From efa285d98d44b12d30b53bde66e3ad7dbe2b171e Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Mon, 22 Oct 2018 13:21:57 -0700
Subject: [PATCH 01/17] feat: search provider foo

---
 src/extension/api/languageFeatures.ts | 1 +
 src/extension/api/search.ts           | 9 +++++++++
 src/extension/extensionHost.ts        | 8 ++++++++
 src/sourcegraph.d.ts                  | 4 ++++
 4 files changed, 22 insertions(+)
 create mode 100644 src/extension/api/search.ts

diff --git a/src/extension/api/languageFeatures.ts b/src/extension/api/languageFeatures.ts
index cb24164..be62a4b 100644
--- a/src/extension/api/languageFeatures.ts
+++ b/src/extension/api/languageFeatures.ts
@@ -14,6 +14,7 @@ import * as plain from '../../protocol/plainTypes'
 import { ProviderMap } from './common'
 import { ExtDocuments } from './documents'
 import { fromHover, fromLocation, toPosition } from './types'
+import { CombineLatestOperator } from 'rxjs/internal/observable/combineLatest'
 
 /** @internal */
 export interface ExtLanguageFeaturesAPI {
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
new file mode 100644
index 0000000..2d10945
--- /dev/null
+++ b/src/extension/api/search.ts
@@ -0,0 +1,9 @@
+/** @internal */
+export interface ExtSearchFeaturesAPI {}
+
+/** @internal */
+export class ExtSearchFeatures implements ExtSearchFeaturesAPI {
+    public foo(): void {
+        console.log('FOO')
+    }
+}
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index d1c4993..1ce81d7 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -8,6 +8,7 @@ import { ExtConfiguration } from './api/configuration'
 import { ExtContext } from './api/context'
 import { ExtDocuments } from './api/documents'
 import { ExtLanguageFeatures } from './api/languageFeatures'
+import { ExtSearchFeatures } from './api/search'
 import { ExtWindows } from './api/windows'
 import { Location } from './types/location'
 import { Position } from './types/position'
@@ -82,6 +83,9 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const languageFeatures = new ExtLanguageFeatures(proxy('languageFeatures'), documents)
     handleRequests(connection, 'languageFeatures', languageFeatures)
 
+    const searchFeatures = new ExtSearchFeatures()
+    handleRequests(connection, 'searchFeatures', searchFeatures)
+
     const commands = new ExtCommands(proxy('commands'))
     handleRequests(connection, 'commands', commands)
 
@@ -129,6 +133,10 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
                 languageFeatures.registerReferenceProvider(selector, provider),
         },
 
+        search: {
+            foo: () => searchFeatures.foo(),
+        },
+
         commands: {
             registerCommand: (command, callback) => commands.registerCommand({ command, callback }),
             executeCommand: (command, ...args) => commands.executeCommand(command, args),
diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index 051f89c..bc14e99 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -717,6 +717,10 @@ declare module 'sourcegraph' {
         ): ProviderResult<Location[]>
     }
 
+    export namespace search {
+        export function foo(): void
+    }
+
     export namespace languages {
         export function registerHoverProvider(selector: DocumentSelector, provider: HoverProvider): Unsubscribable
 

From 5e4fe5bb076195416a6466344a7b548b015847de Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Mon, 22 Oct 2018 18:13:53 -0700
Subject: [PATCH 02/17] feat: can registerSearchProvider

---
 src/client/api/search.ts              | 42 +++++++++++++++++++++++++++
 src/client/controller.ts              |  2 ++
 src/client/providers/search.ts        | 32 ++++++++++++++++++++
 src/client/registries.ts              |  2 ++
 src/common/proxy.ts                   |  7 +++++
 src/extension/api/languageFeatures.ts |  1 -
 src/extension/api/search.ts           | 23 +++++++++++++--
 src/extension/extensionHost.ts        | 10 +++++--
 src/sourcegraph.d.ts                  |  6 +++-
 9 files changed, 117 insertions(+), 8 deletions(-)
 create mode 100644 src/client/api/search.ts
 create mode 100644 src/client/providers/search.ts

diff --git a/src/client/api/search.ts b/src/client/api/search.ts
new file mode 100644
index 0000000..e64cf28
--- /dev/null
+++ b/src/client/api/search.ts
@@ -0,0 +1,42 @@
+import { from, Observable, Subscription } from 'rxjs'
+import { ExtSearchFeaturesAPI } from 'src/extension/api/search'
+import { Connection } from 'src/protocol/jsonrpc2/connection'
+import { createProxyAndHandleRequests } from '../../common/proxy'
+import { FeatureProviderRegistry } from '../providers/registry'
+import { TransformQuerySignature } from '../providers/search'
+import { SubscriptionMap } from './common'
+
+export interface SearchFeaturesAPI {
+    $registerSearchProvider(id: number): void
+    $unregister(id: number): void
+}
+
+export class SearchFeatures implements SearchFeaturesAPI {
+    private subscriptions = new Subscription()
+    private registrations = new SubscriptionMap()
+    private proxy: ExtSearchFeaturesAPI
+
+    constructor(connection: Connection, private searchRegistry: FeatureProviderRegistry<{}, TransformQuerySignature>) {
+        this.subscriptions.add(this.registrations)
+
+        this.proxy = createProxyAndHandleRequests('searchFeatures', connection, this)
+    }
+
+    public $registerSearchProvider(id: number): void {
+        this.registrations.add(
+            id,
+            this.searchRegistry.registerProvider(
+                {},
+                (query: string): Observable<string | null | undefined> => from(this.proxy.$transformQuery(id, query))
+            )
+        )
+    }
+
+    public $unregister(id: number): void {
+        this.registrations.remove(id)
+    }
+
+    public unsubscribe(): void {
+        this.subscriptions.unsubscribe()
+    }
+}
diff --git a/src/client/controller.ts b/src/client/controller.ts
index f4936bc..2918ad0 100644
--- a/src/client/controller.ts
+++ b/src/client/controller.ts
@@ -19,6 +19,7 @@ import { ClientConfiguration } from './api/configuration'
 import { ClientContext } from './api/context'
 import { ClientDocuments } from './api/documents'
 import { ClientLanguageFeatures } from './api/languageFeatures'
+import { SearchFeatures } from './api/search'
 import { ClientWindows } from './api/windows'
 import { applyContextUpdate, EMPTY_CONTEXT } from './context/context'
 import { EMPTY_ENVIRONMENT, Environment } from './environment'
@@ -268,6 +269,7 @@ export class Controller<X extends Extension, C extends ConfigurationCascade> imp
                 this.registries.textDocumentReferences
             )
         )
+        subscription.add(new SearchFeatures(client, this.registries.search))
         subscription.add(new ClientCommands(client, this.registries.commands))
     }
 
diff --git a/src/client/providers/search.ts b/src/client/providers/search.ts
new file mode 100644
index 0000000..e24353b
--- /dev/null
+++ b/src/client/providers/search.ts
@@ -0,0 +1,32 @@
+import { Observable } from 'rxjs'
+import { switchMap } from 'rxjs/operators'
+import { FeatureProviderRegistry } from './registry'
+
+export type TransformQuerySignature = (query: string) => Observable<string | null | undefined>
+/** Provides hovers from all extensions. */
+export class SearchTransformProviderRegistry extends FeatureProviderRegistry<{}, TransformQuerySignature> {
+    public transformQuery(query: string): Observable<string | null | undefined> {
+        return transformQuery(this.providers, query)
+    }
+}
+
+/**
+ * Returns an observable that emits all providers' hovers whenever any of the last-emitted set of providers emits
+ * hovers.
+ *
+ * Most callers should use TextDocumentHoverProviderRegistry's getHover method, which uses the registered hover
+ * providers.
+ */
+export function transformQuery(
+    providers: Observable<TransformQuerySignature[]>,
+    query: string
+): Observable<string | null | undefined> {
+    return providers.pipe(
+        switchMap(providers => {
+            if (providers.length === 0) {
+                return [null]
+            }
+            return providers[0](query)
+        })
+    )
+}
diff --git a/src/client/registries.ts b/src/client/registries.ts
index c1decd0..ec78f95 100644
--- a/src/client/registries.ts
+++ b/src/client/registries.ts
@@ -7,6 +7,7 @@ import { ContributionRegistry } from './providers/contribution'
 import { TextDocumentDecorationProviderRegistry } from './providers/decoration'
 import { TextDocumentHoverProviderRegistry } from './providers/hover'
 import { TextDocumentLocationProviderRegistry, TextDocumentReferencesProviderRegistry } from './providers/location'
+import { SearchTransformProviderRegistry } from './providers/search'
 
 /**
  * Registries is a container for all provider registries.
@@ -25,4 +26,5 @@ export class Registries<X extends Extension, C extends ConfigurationCascade> {
     public readonly textDocumentTypeDefinition = new TextDocumentLocationProviderRegistry()
     public readonly textDocumentHover = new TextDocumentHoverProviderRegistry()
     public readonly textDocumentDecoration = new TextDocumentDecorationProviderRegistry()
+    public readonly search = new SearchTransformProviderRegistry()
 }
diff --git a/src/common/proxy.ts b/src/common/proxy.ts
index aa50072..9697fd9 100644
--- a/src/common/proxy.ts
+++ b/src/common/proxy.ts
@@ -16,8 +16,12 @@ export function createProxy(call: (name: string, args: any[]) => any): any {
     return new Proxy(Object.create(null), {
         get: (target: any, name: string) => {
             if (!target[name] && name[0] === '$') {
+                console.log('intercepting name', name)
                 target[name] = (...args: any[]) => call(name, args)
+            } else {
+                console.log('not intercepting', name)
             }
+
             return target[name]
         },
     })
@@ -36,7 +40,10 @@ export function handleRequests(connection: Connection, prefix: string, handler:
     for (const name of Object.getOwnPropertyNames(proto)) {
         const value = proto[name]
         if (name[0] === '$' && typeof value === 'function') {
+            console.log('registering request handler', name)
             connection.onRequest(`${prefix}/${name}`, (...args: any[]) => value.apply(handler, args[0]))
+        } else {
+            console.log('not registering', name)
         }
     }
 }
diff --git a/src/extension/api/languageFeatures.ts b/src/extension/api/languageFeatures.ts
index be62a4b..cb24164 100644
--- a/src/extension/api/languageFeatures.ts
+++ b/src/extension/api/languageFeatures.ts
@@ -14,7 +14,6 @@ import * as plain from '../../protocol/plainTypes'
 import { ProviderMap } from './common'
 import { ExtDocuments } from './documents'
 import { fromHover, fromLocation, toPosition } from './types'
-import { CombineLatestOperator } from 'rxjs/internal/observable/combineLatest'
 
 /** @internal */
 export interface ExtLanguageFeaturesAPI {
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index 2d10945..5cb80f6 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -1,9 +1,26 @@
+import { Unsubscribable } from 'rxjs'
+import { SearchProvider } from 'sourcegraph'
+import { SearchFeaturesAPI } from 'src/client/api/search'
+import { ProviderMap } from './common'
+
 /** @internal */
-export interface ExtSearchFeaturesAPI {}
+export interface ExtSearchFeaturesAPI {
+    $transformQuery: (id: number, query: string) => Promise<string | null | undefined>
+}
 
 /** @internal */
 export class ExtSearchFeatures implements ExtSearchFeaturesAPI {
-    public foo(): void {
-        console.log('FOO')
+    private registrations = new ProviderMap<SearchProvider>(id => this.proxy.$unregister(id))
+    constructor(private proxy: SearchFeaturesAPI) {}
+
+    public registerSearchProvider(provider: SearchProvider): Unsubscribable {
+        const { id, subscription } = this.registrations.add(provider)
+        this.proxy.$registerSearchProvider(id)
+        return subscription
+    }
+
+    public $transformQuery(id: number, query: string): Promise<string | null | undefined> {
+        const provider = this.registrations.get<SearchProvider>(id)
+        return Promise.resolve(provider.transformQuery(query))
     }
 }
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index 1ce81d7..17c6017 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -66,7 +66,11 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const sync = () => connection.sendRequest<void>('ping')
     connection.onRequest('ping', () => 'pong')
 
-    const proxy = (prefix: string) => createProxy((name, args) => connection.sendRequest(`${prefix}/${name}`, args))
+    const proxy = (prefix: string) =>
+        createProxy((name, args) => {
+            console.log('proxy calling send request', name)
+            connection.sendRequest(`${prefix}/${name}`, args)
+        })
 
     const context = new ExtContext(proxy('context'))
     handleRequests(connection, 'context', context)
@@ -83,7 +87,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const languageFeatures = new ExtLanguageFeatures(proxy('languageFeatures'), documents)
     handleRequests(connection, 'languageFeatures', languageFeatures)
 
-    const searchFeatures = new ExtSearchFeatures()
+    const searchFeatures = new ExtSearchFeatures(proxy('searchFeatures'))
     handleRequests(connection, 'searchFeatures', searchFeatures)
 
     const commands = new ExtCommands(proxy('commands'))
@@ -134,7 +138,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
         },
 
         search: {
-            foo: () => searchFeatures.foo(),
+            registerSearchProvider: provider => searchFeatures.registerSearchProvider(provider),
         },
 
         commands: {
diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index bc14e99..b70d61b 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -717,8 +717,12 @@ declare module 'sourcegraph' {
         ): ProviderResult<Location[]>
     }
 
+    export interface SearchProvider {
+        transformQuery(query: string): ProviderResult<string>
+    }
+
     export namespace search {
-        export function foo(): void
+        export function registerSearchProvider(provider: SearchProvider): Unsubscribable
     }
 
     export namespace languages {

From de15667e2a26c0033ecb7d482e0d84b7cc68837f Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Tue, 23 Oct 2018 09:46:09 -0700
Subject: [PATCH 03/17] fix: clean up

---
 src/common/proxy.ts            | 6 ------
 src/extension/extensionHost.ts | 6 +-----
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/src/common/proxy.ts b/src/common/proxy.ts
index 9697fd9..ed8ed87 100644
--- a/src/common/proxy.ts
+++ b/src/common/proxy.ts
@@ -16,10 +16,7 @@ export function createProxy(call: (name: string, args: any[]) => any): any {
     return new Proxy(Object.create(null), {
         get: (target: any, name: string) => {
             if (!target[name] && name[0] === '$') {
-                console.log('intercepting name', name)
                 target[name] = (...args: any[]) => call(name, args)
-            } else {
-                console.log('not intercepting', name)
             }
 
             return target[name]
@@ -40,10 +37,7 @@ export function handleRequests(connection: Connection, prefix: string, handler:
     for (const name of Object.getOwnPropertyNames(proto)) {
         const value = proto[name]
         if (name[0] === '$' && typeof value === 'function') {
-            console.log('registering request handler', name)
             connection.onRequest(`${prefix}/${name}`, (...args: any[]) => value.apply(handler, args[0]))
-        } else {
-            console.log('not registering', name)
         }
     }
 }
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index 17c6017..64520b9 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -66,11 +66,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const sync = () => connection.sendRequest<void>('ping')
     connection.onRequest('ping', () => 'pong')
 
-    const proxy = (prefix: string) =>
-        createProxy((name, args) => {
-            console.log('proxy calling send request', name)
-            connection.sendRequest(`${prefix}/${name}`, args)
-        })
+    const proxy = (prefix: string) => createProxy((name, args) => connection.sendRequest(`${prefix}/${name}`, args))
 
     const context = new ExtContext(proxy('context'))
     handleRequests(connection, 'context', context)

From f5fd2be41e2283f22d09fb3d0ac3c2832a1ef9ec Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Tue, 23 Oct 2018 16:58:13 -0700
Subject: [PATCH 04/17] feat: return original query if no providers

---
 src/client/providers/search.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/client/providers/search.ts b/src/client/providers/search.ts
index e24353b..e975a88 100644
--- a/src/client/providers/search.ts
+++ b/src/client/providers/search.ts
@@ -24,7 +24,7 @@ export function transformQuery(
     return providers.pipe(
         switchMap(providers => {
             if (providers.length === 0) {
-                return [null]
+                return [query]
             }
             return providers[0](query)
         })

From e10a9fc394c6b85ca0b93fa3c863443c6ecc287a Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Tue, 23 Oct 2018 17:50:12 -0700
Subject: [PATCH 05/17] docs: update docs

---
 src/client/providers/search.ts | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/client/providers/search.ts b/src/client/providers/search.ts
index e975a88..6a7e985 100644
--- a/src/client/providers/search.ts
+++ b/src/client/providers/search.ts
@@ -3,7 +3,8 @@ import { switchMap } from 'rxjs/operators'
 import { FeatureProviderRegistry } from './registry'
 
 export type TransformQuerySignature = (query: string) => Observable<string | null | undefined>
-/** Provides hovers from all extensions. */
+
+/** Provides transformed queries from the first search extension. */
 export class SearchTransformProviderRegistry extends FeatureProviderRegistry<{}, TransformQuerySignature> {
     public transformQuery(query: string): Observable<string | null | undefined> {
         return transformQuery(this.providers, query)
@@ -11,10 +12,10 @@ export class SearchTransformProviderRegistry extends FeatureProviderRegistry<{},
 }
 
 /**
- * Returns an observable that emits all providers' hovers whenever any of the last-emitted set of providers emits
- * hovers.
+ * Returns an observable that emits the first provider's transformed query whenever any of the last-emitted set of providers emits
+ * a query.
  *
- * Most callers should use TextDocumentHoverProviderRegistry's getHover method, which uses the registered hover
+ * Most callers should use SearchTransformProviderRegistry's getHover method, which uses the registered search
  * providers.
  */
 export function transformQuery(

From 25ca64bf0a7a424a33d36aa8a64e6e75d3f61ffa Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 10:59:43 -0700
Subject: [PATCH 06/17] chore: rename SearchProvider to QueryTransformProvider

---
 src/client/api/search.ts       |  4 ++--
 src/extension/api/search.ts    | 10 +++++-----
 src/extension/extensionHost.ts |  2 +-
 src/sourcegraph.d.ts           |  4 ++--
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/client/api/search.ts b/src/client/api/search.ts
index e64cf28..d82aab4 100644
--- a/src/client/api/search.ts
+++ b/src/client/api/search.ts
@@ -7,7 +7,7 @@ import { TransformQuerySignature } from '../providers/search'
 import { SubscriptionMap } from './common'
 
 export interface SearchFeaturesAPI {
-    $registerSearchProvider(id: number): void
+    $registerQueryTransformProvider(id: number): void
     $unregister(id: number): void
 }
 
@@ -22,7 +22,7 @@ export class SearchFeatures implements SearchFeaturesAPI {
         this.proxy = createProxyAndHandleRequests('searchFeatures', connection, this)
     }
 
-    public $registerSearchProvider(id: number): void {
+    public $registerQueryTransformProvider(id: number): void {
         this.registrations.add(
             id,
             this.searchRegistry.registerProvider(
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index 5cb80f6..8412e23 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -1,5 +1,5 @@
 import { Unsubscribable } from 'rxjs'
-import { SearchProvider } from 'sourcegraph'
+import { QueryTransformProvider } from 'sourcegraph'
 import { SearchFeaturesAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
@@ -10,17 +10,17 @@ export interface ExtSearchFeaturesAPI {
 
 /** @internal */
 export class ExtSearchFeatures implements ExtSearchFeaturesAPI {
-    private registrations = new ProviderMap<SearchProvider>(id => this.proxy.$unregister(id))
+    private registrations = new ProviderMap<QueryTransformProvider>(id => this.proxy.$unregister(id))
     constructor(private proxy: SearchFeaturesAPI) {}
 
-    public registerSearchProvider(provider: SearchProvider): Unsubscribable {
+    public registerQueryTransformProvider(provider: QueryTransformProvider): Unsubscribable {
         const { id, subscription } = this.registrations.add(provider)
-        this.proxy.$registerSearchProvider(id)
+        this.proxy.$registerQueryTransformProvider(id)
         return subscription
     }
 
     public $transformQuery(id: number, query: string): Promise<string | null | undefined> {
-        const provider = this.registrations.get<SearchProvider>(id)
+        const provider = this.registrations.get<QueryTransformProvider>(id)
         return Promise.resolve(provider.transformQuery(query))
     }
 }
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index 64520b9..9a01b67 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -134,7 +134,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
         },
 
         search: {
-            registerSearchProvider: provider => searchFeatures.registerSearchProvider(provider),
+            registerQueryTransformProvider: provider => searchFeatures.registerQueryTransformProvider(provider),
         },
 
         commands: {
diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index b70d61b..749557a 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -717,12 +717,12 @@ declare module 'sourcegraph' {
         ): ProviderResult<Location[]>
     }
 
-    export interface SearchProvider {
+    export interface QueryTransformProvider {
         transformQuery(query: string): ProviderResult<string>
     }
 
     export namespace search {
-        export function registerSearchProvider(provider: SearchProvider): Unsubscribable
+        export function registerQueryTransformProvider(provider: QueryTransformProvider): Unsubscribable
     }
 
     export namespace languages {

From c76d18cc02328b8ffe72fa6e200e8a60271a35b5 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 18:21:03 -0700
Subject: [PATCH 07/17] fix: improve naming

---
 src/client/api/search.ts                 | 14 ++++----
 src/client/controller.ts                 |  4 +--
 src/client/providers/queryTransformer.ts | 45 ++++++++++++++++++++++++
 src/client/providers/search.ts           | 33 -----------------
 src/client/registries.ts                 |  4 +--
 src/extension/api/search.ts              | 18 +++++-----
 src/extension/extensionHost.ts           |  6 ++--
 src/sourcegraph.d.ts                     |  4 +--
 8 files changed, 70 insertions(+), 58 deletions(-)
 create mode 100644 src/client/providers/queryTransformer.ts
 delete mode 100644 src/client/providers/search.ts

diff --git a/src/client/api/search.ts b/src/client/api/search.ts
index d82aab4..9b7d07e 100644
--- a/src/client/api/search.ts
+++ b/src/client/api/search.ts
@@ -1,20 +1,20 @@
 import { from, Observable, Subscription } from 'rxjs'
-import { ExtSearchFeaturesAPI } from 'src/extension/api/search'
+import { ExtSearch } from 'src/extension/api/search'
 import { Connection } from 'src/protocol/jsonrpc2/connection'
 import { createProxyAndHandleRequests } from '../../common/proxy'
+import { TransformQuerySignature } from '../providers/queryTransformer'
 import { FeatureProviderRegistry } from '../providers/registry'
-import { TransformQuerySignature } from '../providers/search'
 import { SubscriptionMap } from './common'
 
-export interface SearchFeaturesAPI {
-    $registerQueryTransformProvider(id: number): void
+export interface SearchAPI {
+    $registerQueryTransformer(id: number): void
     $unregister(id: number): void
 }
 
-export class SearchFeatures implements SearchFeaturesAPI {
+export class Search implements SearchAPI {
     private subscriptions = new Subscription()
     private registrations = new SubscriptionMap()
-    private proxy: ExtSearchFeaturesAPI
+    private proxy: ExtSearch
 
     constructor(connection: Connection, private searchRegistry: FeatureProviderRegistry<{}, TransformQuerySignature>) {
         this.subscriptions.add(this.registrations)
@@ -22,7 +22,7 @@ export class SearchFeatures implements SearchFeaturesAPI {
         this.proxy = createProxyAndHandleRequests('searchFeatures', connection, this)
     }
 
-    public $registerQueryTransformProvider(id: number): void {
+    public $registerQueryTransformer(id: number): void {
         this.registrations.add(
             id,
             this.searchRegistry.registerProvider(
diff --git a/src/client/controller.ts b/src/client/controller.ts
index 2918ad0..1afe818 100644
--- a/src/client/controller.ts
+++ b/src/client/controller.ts
@@ -19,7 +19,7 @@ import { ClientConfiguration } from './api/configuration'
 import { ClientContext } from './api/context'
 import { ClientDocuments } from './api/documents'
 import { ClientLanguageFeatures } from './api/languageFeatures'
-import { SearchFeatures } from './api/search'
+import { Search } from './api/search'
 import { ClientWindows } from './api/windows'
 import { applyContextUpdate, EMPTY_CONTEXT } from './context/context'
 import { EMPTY_ENVIRONMENT, Environment } from './environment'
@@ -269,7 +269,7 @@ export class Controller<X extends Extension, C extends ConfigurationCascade> imp
                 this.registries.textDocumentReferences
             )
         )
-        subscription.add(new SearchFeatures(client, this.registries.search))
+        subscription.add(new Search(client, this.registries.search))
         subscription.add(new ClientCommands(client, this.registries.commands))
     }
 
diff --git a/src/client/providers/queryTransformer.ts b/src/client/providers/queryTransformer.ts
new file mode 100644
index 0000000..e164c79
--- /dev/null
+++ b/src/client/providers/queryTransformer.ts
@@ -0,0 +1,45 @@
+import { Observable, of } from 'rxjs'
+import { flatMap, map, switchMap } from 'rxjs/operators'
+import { FeatureProviderRegistry } from './registry'
+
+export type TransformQuerySignature = (query: string) => Observable<string | null | undefined>
+
+/** Provides transformed queries from the first search extension. */
+export class QueryTransformerRegistry extends FeatureProviderRegistry<{}, TransformQuerySignature> {
+    public transformQuery(query: string): Observable<string | null | undefined> {
+        return transformQuery(this.providers, query)
+    }
+}
+
+/**
+ * Returns an observable that emits all provider's transformed query whenever any of the last-emitted set of providers emits
+ * a query.
+ *
+ * Most callers should use QueryTransformerRegistry's transformQuery method, which uses the registered search
+ * providers.
+ */
+export function transformQuery(
+    providers: Observable<TransformQuerySignature[]>,
+    query: string
+): Observable<string | null | undefined> {
+    return providers.pipe(
+        switchMap(providers => {
+            if (providers.length === 0) {
+                return [query]
+            }
+            // let currentQuery = providers[0](query).pipe(map(q => q))
+            // for (const provider of providers) {
+            //     const str = currentQuery.subscribe()
+            //     currentQuery = provider()
+            // }
+            return providers.reduce(
+                (currentQuery, transformQuery) =>
+                    currentQuery.pipe(
+                        flatMap(q => transformQuery(q).pipe(map(transformedQuery => transformedQuery || q)))
+                    ),
+                of(query)
+            )
+            // of(providers).pipe(reduce((accumulatedValue, currentProvider) => currentProvider(accumulatedValue)), providers[0](query)))
+        })
+    )
+}
diff --git a/src/client/providers/search.ts b/src/client/providers/search.ts
deleted file mode 100644
index 6a7e985..0000000
--- a/src/client/providers/search.ts
+++ /dev/null
@@ -1,33 +0,0 @@
-import { Observable } from 'rxjs'
-import { switchMap } from 'rxjs/operators'
-import { FeatureProviderRegistry } from './registry'
-
-export type TransformQuerySignature = (query: string) => Observable<string | null | undefined>
-
-/** Provides transformed queries from the first search extension. */
-export class SearchTransformProviderRegistry extends FeatureProviderRegistry<{}, TransformQuerySignature> {
-    public transformQuery(query: string): Observable<string | null | undefined> {
-        return transformQuery(this.providers, query)
-    }
-}
-
-/**
- * Returns an observable that emits the first provider's transformed query whenever any of the last-emitted set of providers emits
- * a query.
- *
- * Most callers should use SearchTransformProviderRegistry's getHover method, which uses the registered search
- * providers.
- */
-export function transformQuery(
-    providers: Observable<TransformQuerySignature[]>,
-    query: string
-): Observable<string | null | undefined> {
-    return providers.pipe(
-        switchMap(providers => {
-            if (providers.length === 0) {
-                return [query]
-            }
-            return providers[0](query)
-        })
-    )
-}
diff --git a/src/client/registries.ts b/src/client/registries.ts
index ec78f95..1eb20f3 100644
--- a/src/client/registries.ts
+++ b/src/client/registries.ts
@@ -7,7 +7,7 @@ import { ContributionRegistry } from './providers/contribution'
 import { TextDocumentDecorationProviderRegistry } from './providers/decoration'
 import { TextDocumentHoverProviderRegistry } from './providers/hover'
 import { TextDocumentLocationProviderRegistry, TextDocumentReferencesProviderRegistry } from './providers/location'
-import { SearchTransformProviderRegistry } from './providers/search'
+import { QueryTransformerRegistry } from './providers/queryTransformer'
 
 /**
  * Registries is a container for all provider registries.
@@ -26,5 +26,5 @@ export class Registries<X extends Extension, C extends ConfigurationCascade> {
     public readonly textDocumentTypeDefinition = new TextDocumentLocationProviderRegistry()
     public readonly textDocumentHover = new TextDocumentHoverProviderRegistry()
     public readonly textDocumentDecoration = new TextDocumentDecorationProviderRegistry()
-    public readonly search = new SearchTransformProviderRegistry()
+    public readonly search = new QueryTransformerRegistry()
 }
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index 8412e23..e7def54 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -1,26 +1,26 @@
 import { Unsubscribable } from 'rxjs'
-import { QueryTransformProvider } from 'sourcegraph'
-import { SearchFeaturesAPI } from 'src/client/api/search'
+import { QueryTransformerProvider } from 'sourcegraph'
+import { SearchAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
 /** @internal */
-export interface ExtSearchFeaturesAPI {
+export interface ExtSearchAPI {
     $transformQuery: (id: number, query: string) => Promise<string | null | undefined>
 }
 
 /** @internal */
-export class ExtSearchFeatures implements ExtSearchFeaturesAPI {
-    private registrations = new ProviderMap<QueryTransformProvider>(id => this.proxy.$unregister(id))
-    constructor(private proxy: SearchFeaturesAPI) {}
+export class ExtSearch implements ExtSearchAPI {
+    private registrations = new ProviderMap<QueryTransformerProvider>(id => this.proxy.$unregister(id))
+    constructor(private proxy: SearchAPI) {}
 
-    public registerQueryTransformProvider(provider: QueryTransformProvider): Unsubscribable {
+    public registerQueryTransformer(provider: QueryTransformerProvider): Unsubscribable {
         const { id, subscription } = this.registrations.add(provider)
-        this.proxy.$registerQueryTransformProvider(id)
+        this.proxy.$registerQueryTransformer(id)
         return subscription
     }
 
     public $transformQuery(id: number, query: string): Promise<string | null | undefined> {
-        const provider = this.registrations.get<QueryTransformProvider>(id)
+        const provider = this.registrations.get<QueryTransformerProvider>(id)
         return Promise.resolve(provider.transformQuery(query))
     }
 }
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index 9a01b67..d45048b 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -8,7 +8,7 @@ import { ExtConfiguration } from './api/configuration'
 import { ExtContext } from './api/context'
 import { ExtDocuments } from './api/documents'
 import { ExtLanguageFeatures } from './api/languageFeatures'
-import { ExtSearchFeatures } from './api/search'
+import { ExtSearch } from './api/search'
 import { ExtWindows } from './api/windows'
 import { Location } from './types/location'
 import { Position } from './types/position'
@@ -83,7 +83,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const languageFeatures = new ExtLanguageFeatures(proxy('languageFeatures'), documents)
     handleRequests(connection, 'languageFeatures', languageFeatures)
 
-    const searchFeatures = new ExtSearchFeatures(proxy('searchFeatures'))
+    const searchFeatures = new ExtSearch(proxy('searchFeatures'))
     handleRequests(connection, 'searchFeatures', searchFeatures)
 
     const commands = new ExtCommands(proxy('commands'))
@@ -134,7 +134,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
         },
 
         search: {
-            registerQueryTransformProvider: provider => searchFeatures.registerQueryTransformProvider(provider),
+            registerQueryTransformer: provider => searchFeatures.registerQueryTransformer(provider),
         },
 
         commands: {
diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index 749557a..81ba84e 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -717,12 +717,12 @@ declare module 'sourcegraph' {
         ): ProviderResult<Location[]>
     }
 
-    export interface QueryTransformProvider {
+    export interface QueryTransformerProvider {
         transformQuery(query: string): ProviderResult<string>
     }
 
     export namespace search {
-        export function registerQueryTransformProvider(provider: QueryTransformProvider): Unsubscribable
+        export function registerQueryTransformer(provider: QueryTransformerProvider): Unsubscribable
     }
 
     export namespace languages {

From 8a1c7aa78c978337626afea8f588dcebe6c9b0d6 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 18:24:37 -0700
Subject: [PATCH 08/17] chore: add tests for queryTransformer

---
 src/client/providers/queryTransformer.test.ts | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 src/client/providers/queryTransformer.test.ts

diff --git a/src/client/providers/queryTransformer.test.ts b/src/client/providers/queryTransformer.test.ts
new file mode 100644
index 0000000..468b857
--- /dev/null
+++ b/src/client/providers/queryTransformer.test.ts
@@ -0,0 +1,66 @@
+import * as assert from 'assert'
+import { of } from 'rxjs'
+import { TestScheduler } from 'rxjs/testing'
+import { transformQuery, TransformQuerySignature } from './queryTransformer'
+
+const scheduler = () => new TestScheduler((a, b) => assert.deepStrictEqual(a, b))
+
+const FIXTURE_INPUT = 'foo'
+const FIXTURE_RESULT_MERGED = 'foo bar'
+const FIXTURE_RESULT = 'bar'
+
+describe('transformQuery', () => {
+    describe('0 providers', () => {
+        it('returns original query', () =>
+            scheduler().run(({ cold, expectObservable }) =>
+                expectObservable(
+                    transformQuery(cold<TransformQuerySignature[]>('-a-|', { a: [] }), FIXTURE_INPUT)
+                ).toBe('-a-|', {
+                    a: FIXTURE_INPUT,
+                })
+            ))
+    })
+
+    describe('1 provider', () => {
+        it('returns result from provider', () =>
+            scheduler().run(({ cold, expectObservable }) =>
+                expectObservable(
+                    transformQuery(
+                        cold<TransformQuerySignature[]>('-a-|', {
+                            a: [q => of(FIXTURE_RESULT)],
+                        }),
+                        FIXTURE_INPUT
+                    )
+                ).toBe('-a-|', { a: FIXTURE_RESULT })
+            ))
+    })
+
+    describe('2 providers', () => {
+        it('returns a single query transformed by both providers', () =>
+            scheduler().run(({ cold, expectObservable }) =>
+                expectObservable(
+                    transformQuery(
+                        cold<TransformQuerySignature[]>('-a-|', {
+                            a: [q => of(q), q => of(`${q} ${FIXTURE_RESULT}`)],
+                        }),
+                        FIXTURE_INPUT
+                    )
+                ).toBe('-a-|', { a: FIXTURE_RESULT_MERGED })
+            ))
+    })
+
+    describe('Multiple emissions', () => {
+        it('returns stream of results', () =>
+            scheduler().run(({ cold, expectObservable }) =>
+                expectObservable(
+                    transformQuery(
+                        cold<TransformQuerySignature[]>('-a-b-|', {
+                            a: [q => of(q)],
+                            b: [q => of(FIXTURE_RESULT)],
+                        }),
+                        FIXTURE_INPUT
+                    )
+                ).toBe('-a-b-|', { a: FIXTURE_INPUT, b: FIXTURE_RESULT })
+            ))
+    })
+})

From 39590b952d832f4f0faea27231af068f34fe4087 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 18:36:14 -0700
Subject: [PATCH 09/17] fix: remove commented chaining attempts

---
 src/client/providers/queryTransformer.ts | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/src/client/providers/queryTransformer.ts b/src/client/providers/queryTransformer.ts
index e164c79..665caa1 100644
--- a/src/client/providers/queryTransformer.ts
+++ b/src/client/providers/queryTransformer.ts
@@ -12,7 +12,7 @@ export class QueryTransformerRegistry extends FeatureProviderRegistry<{}, Transf
 }
 
 /**
- * Returns an observable that emits all provider's transformed query whenever any of the last-emitted set of providers emits
+ * Returns an observable that emits a query transformed by all providers whenever any of the last-emitted set of providers emits
  * a query.
  *
  * Most callers should use QueryTransformerRegistry's transformQuery method, which uses the registered search
@@ -27,11 +27,6 @@ export function transformQuery(
             if (providers.length === 0) {
                 return [query]
             }
-            // let currentQuery = providers[0](query).pipe(map(q => q))
-            // for (const provider of providers) {
-            //     const str = currentQuery.subscribe()
-            //     currentQuery = provider()
-            // }
             return providers.reduce(
                 (currentQuery, transformQuery) =>
                     currentQuery.pipe(
@@ -39,7 +34,6 @@ export function transformQuery(
                     ),
                 of(query)
             )
-            // of(providers).pipe(reduce((accumulatedValue, currentProvider) => currentProvider(accumulatedValue)), providers[0](query)))
         })
     )
 }

From 4847f2bd81be2daf439392ff7dcef982af616f0a Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 18:45:54 -0700
Subject: [PATCH 10/17] fix: more renames and cleanup

---
 src/client/api/search.ts | 7 +++++--
 src/client/controller.ts | 2 +-
 src/client/registries.ts | 2 +-
 src/common/proxy.ts      | 1 -
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/client/api/search.ts b/src/client/api/search.ts
index 9b7d07e..bb8a011 100644
--- a/src/client/api/search.ts
+++ b/src/client/api/search.ts
@@ -16,7 +16,10 @@ export class Search implements SearchAPI {
     private registrations = new SubscriptionMap()
     private proxy: ExtSearch
 
-    constructor(connection: Connection, private searchRegistry: FeatureProviderRegistry<{}, TransformQuerySignature>) {
+    constructor(
+        connection: Connection,
+        private queryTransformerRegistry: FeatureProviderRegistry<{}, TransformQuerySignature>
+    ) {
         this.subscriptions.add(this.registrations)
 
         this.proxy = createProxyAndHandleRequests('searchFeatures', connection, this)
@@ -25,7 +28,7 @@ export class Search implements SearchAPI {
     public $registerQueryTransformer(id: number): void {
         this.registrations.add(
             id,
-            this.searchRegistry.registerProvider(
+            this.queryTransformerRegistry.registerProvider(
                 {},
                 (query: string): Observable<string | null | undefined> => from(this.proxy.$transformQuery(id, query))
             )
diff --git a/src/client/controller.ts b/src/client/controller.ts
index 1afe818..9ff66be 100644
--- a/src/client/controller.ts
+++ b/src/client/controller.ts
@@ -269,7 +269,7 @@ export class Controller<X extends Extension, C extends ConfigurationCascade> imp
                 this.registries.textDocumentReferences
             )
         )
-        subscription.add(new Search(client, this.registries.search))
+        subscription.add(new Search(client, this.registries.queryTransformer))
         subscription.add(new ClientCommands(client, this.registries.commands))
     }
 
diff --git a/src/client/registries.ts b/src/client/registries.ts
index 1eb20f3..59e6640 100644
--- a/src/client/registries.ts
+++ b/src/client/registries.ts
@@ -26,5 +26,5 @@ export class Registries<X extends Extension, C extends ConfigurationCascade> {
     public readonly textDocumentTypeDefinition = new TextDocumentLocationProviderRegistry()
     public readonly textDocumentHover = new TextDocumentHoverProviderRegistry()
     public readonly textDocumentDecoration = new TextDocumentDecorationProviderRegistry()
-    public readonly search = new QueryTransformerRegistry()
+    public readonly queryTransformer = new QueryTransformerRegistry()
 }
diff --git a/src/common/proxy.ts b/src/common/proxy.ts
index ed8ed87..aa50072 100644
--- a/src/common/proxy.ts
+++ b/src/common/proxy.ts
@@ -18,7 +18,6 @@ export function createProxy(call: (name: string, args: any[]) => any): any {
             if (!target[name] && name[0] === '$') {
                 target[name] = (...args: any[]) => call(name, args)
             }
-
             return target[name]
         },
     })

From 13e53ba050261804898c0d086c8a314631b5e5c6 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Wed, 24 Oct 2018 23:44:49 -0700
Subject: [PATCH 11/17] chore: add integration test

---
 src/integration-test/search.test.ts | 46 +++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 src/integration-test/search.test.ts

diff --git a/src/integration-test/search.test.ts b/src/integration-test/search.test.ts
new file mode 100644
index 0000000..16ff881
--- /dev/null
+++ b/src/integration-test/search.test.ts
@@ -0,0 +1,46 @@
+import * as assert from 'assert'
+import { take } from 'rxjs/operators'
+import { integrationTestContext } from './helpers.test'
+
+describe('search (integration)', () => {
+    it('registers a query transformer', async () => {
+        const { clientController, extensionHost, ready } = await integrationTestContext()
+
+        // Register the provider and call it
+        const unsubscribe = extensionHost.search.registerQueryTransformer({ transformQuery: () => 'bar' })
+        await ready
+        assert.deepStrictEqual(
+            await clientController.registries.queryTransformer
+                .transformQuery('foo')
+                .pipe(take(1))
+                .toPromise(),
+            'bar'
+        )
+
+        // Unregister the provider and ensure it's removed
+        unsubscribe.unsubscribe()
+        assert.deepStrictEqual(
+            await clientController.registries.queryTransformer
+                .transformQuery('foo')
+                .pipe(take(1))
+                .toPromise(),
+            'foo'
+        )
+    })
+
+    it('supports multiple query transformers', async () => {
+        const { clientController, extensionHost, ready } = await integrationTestContext()
+
+        // Register the provider and call it
+        extensionHost.search.registerQueryTransformer({ transformQuery: q => `${q} bar` })
+        extensionHost.search.registerQueryTransformer({ transformQuery: q => `${q} baz` })
+        await ready
+        assert.deepStrictEqual(
+            await clientController.registries.queryTransformer
+                .transformQuery('foo')
+                .pipe(take(1))
+                .toPromise(),
+            'foo bar baz'
+        )
+    })
+})

From 4bbef152809446f35607b59531d11a5db09f2f58 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 11:38:17 -0700
Subject: [PATCH 12/17] fix: address comments

---
 src/client/api/search.ts                      |  6 ++-
 src/client/providers/queryTransformer.test.ts | 14 ++++---
 src/client/providers/queryTransformer.ts      | 19 ++++-----
 src/extension/api/search.ts                   | 12 +++---
 src/extension/extensionHost.ts                |  6 +--
 src/integration-test/search.test.ts           |  6 +--
 src/sourcegraph.d.ts                          | 40 +++++++++++++++----
 7 files changed, 64 insertions(+), 39 deletions(-)

diff --git a/src/client/api/search.ts b/src/client/api/search.ts
index bb8a011..22d1d30 100644
--- a/src/client/api/search.ts
+++ b/src/client/api/search.ts
@@ -6,11 +6,13 @@ import { TransformQuerySignature } from '../providers/queryTransformer'
 import { FeatureProviderRegistry } from '../providers/registry'
 import { SubscriptionMap } from './common'
 
+/** @internal */
 export interface SearchAPI {
     $registerQueryTransformer(id: number): void
     $unregister(id: number): void
 }
 
+/** @internal */
 export class Search implements SearchAPI {
     private subscriptions = new Subscription()
     private registrations = new SubscriptionMap()
@@ -22,7 +24,7 @@ export class Search implements SearchAPI {
     ) {
         this.subscriptions.add(this.registrations)
 
-        this.proxy = createProxyAndHandleRequests('searchFeatures', connection, this)
+        this.proxy = createProxyAndHandleRequests('search', connection, this)
     }
 
     public $registerQueryTransformer(id: number): void {
@@ -30,7 +32,7 @@ export class Search implements SearchAPI {
             id,
             this.queryTransformerRegistry.registerProvider(
                 {},
-                (query: string): Observable<string | null | undefined> => from(this.proxy.$transformQuery(id, query))
+                (query: string): Observable<string> => from(this.proxy.$transformQuery(id, query))
             )
         )
     }
diff --git a/src/client/providers/queryTransformer.test.ts b/src/client/providers/queryTransformer.test.ts
index 468b857..766b2e4 100644
--- a/src/client/providers/queryTransformer.test.ts
+++ b/src/client/providers/queryTransformer.test.ts
@@ -6,8 +6,9 @@ import { transformQuery, TransformQuerySignature } from './queryTransformer'
 const scheduler = () => new TestScheduler((a, b) => assert.deepStrictEqual(a, b))
 
 const FIXTURE_INPUT = 'foo'
-const FIXTURE_RESULT_MERGED = 'foo bar'
 const FIXTURE_RESULT = 'bar'
+const FIXTURE_RESULT_TWO = 'qux'
+const FIXTURE_RESULT_MERGED = 'foo bar qux'
 
 describe('transformQuery', () => {
     describe('0 providers', () => {
@@ -41,7 +42,7 @@ describe('transformQuery', () => {
                 expectObservable(
                     transformQuery(
                         cold<TransformQuerySignature[]>('-a-|', {
-                            a: [q => of(q), q => of(`${q} ${FIXTURE_RESULT}`)],
+                            a: [q => of(`${q} ${FIXTURE_RESULT}`), q => of(`${q} ${FIXTURE_RESULT_TWO}`)],
                         }),
                         FIXTURE_INPUT
                     )
@@ -55,12 +56,15 @@ describe('transformQuery', () => {
                 expectObservable(
                     transformQuery(
                         cold<TransformQuerySignature[]>('-a-b-|', {
-                            a: [q => of(q)],
-                            b: [q => of(FIXTURE_RESULT)],
+                            a: [q => of(`${q} ${FIXTURE_RESULT}`)],
+                            b: [q => of(`${q} ${FIXTURE_RESULT_TWO}`)],
                         }),
                         FIXTURE_INPUT
                     )
-                ).toBe('-a-b-|', { a: FIXTURE_INPUT, b: FIXTURE_RESULT })
+                ).toBe('-a-b-|', {
+                    a: `${FIXTURE_INPUT} ${FIXTURE_RESULT}`,
+                    b: `${FIXTURE_INPUT} ${FIXTURE_RESULT_TWO}`,
+                })
             ))
     })
 })
diff --git a/src/client/providers/queryTransformer.ts b/src/client/providers/queryTransformer.ts
index 665caa1..ae32f24 100644
--- a/src/client/providers/queryTransformer.ts
+++ b/src/client/providers/queryTransformer.ts
@@ -2,11 +2,11 @@ import { Observable, of } from 'rxjs'
 import { flatMap, map, switchMap } from 'rxjs/operators'
 import { FeatureProviderRegistry } from './registry'
 
-export type TransformQuerySignature = (query: string) => Observable<string | null | undefined>
+export type TransformQuerySignature = (query: string) => Observable<string>
 
-/** Provides transformed queries from the first search extension. */
+/** Transforms search queries using registered query transformers from extensions. */
 export class QueryTransformerRegistry extends FeatureProviderRegistry<{}, TransformQuerySignature> {
-    public transformQuery(query: string): Observable<string | null | undefined> {
+    public transformQuery(query: string): Observable<string> {
         return transformQuery(this.providers, query)
     }
 }
@@ -15,13 +15,10 @@ export class QueryTransformerRegistry extends FeatureProviderRegistry<{}, Transf
  * Returns an observable that emits a query transformed by all providers whenever any of the last-emitted set of providers emits
  * a query.
  *
- * Most callers should use QueryTransformerRegistry's transformQuery method, which uses the registered search
- * providers.
+ * Most callers should use QueryTransformerRegistry's transformQuery method, which uses the registered query transformers
+ *
  */
-export function transformQuery(
-    providers: Observable<TransformQuerySignature[]>,
-    query: string
-): Observable<string | null | undefined> {
+export function transformQuery(providers: Observable<TransformQuerySignature[]>, query: string): Observable<string> {
     return providers.pipe(
         switchMap(providers => {
             if (providers.length === 0) {
@@ -29,9 +26,7 @@ export function transformQuery(
             }
             return providers.reduce(
                 (currentQuery, transformQuery) =>
-                    currentQuery.pipe(
-                        flatMap(q => transformQuery(q).pipe(map(transformedQuery => transformedQuery || q)))
-                    ),
+                    currentQuery.pipe(flatMap(q => transformQuery(q).pipe(map(transformedQuery => transformedQuery)))),
                 of(query)
             )
         })
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index e7def54..ea8863b 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -1,26 +1,26 @@
 import { Unsubscribable } from 'rxjs'
-import { QueryTransformerProvider } from 'sourcegraph'
+import { QueryTransformer } from 'sourcegraph'
 import { SearchAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
 /** @internal */
 export interface ExtSearchAPI {
-    $transformQuery: (id: number, query: string) => Promise<string | null | undefined>
+    $transformQuery: (id: number, query: string) => Promise<string>
 }
 
 /** @internal */
 export class ExtSearch implements ExtSearchAPI {
-    private registrations = new ProviderMap<QueryTransformerProvider>(id => this.proxy.$unregister(id))
+    private registrations = new ProviderMap<QueryTransformer>(id => this.proxy.$unregister(id))
     constructor(private proxy: SearchAPI) {}
 
-    public registerQueryTransformer(provider: QueryTransformerProvider): Unsubscribable {
+    public registerQueryTransformer(provider: QueryTransformer): Unsubscribable {
         const { id, subscription } = this.registrations.add(provider)
         this.proxy.$registerQueryTransformer(id)
         return subscription
     }
 
-    public $transformQuery(id: number, query: string): Promise<string | null | undefined> {
-        const provider = this.registrations.get<QueryTransformerProvider>(id)
+    public $transformQuery(id: number, query: string): Promise<string> {
+        const provider = this.registrations.get<QueryTransformer>(id)
         return Promise.resolve(provider.transformQuery(query))
     }
 }
diff --git a/src/extension/extensionHost.ts b/src/extension/extensionHost.ts
index d45048b..7bb8724 100644
--- a/src/extension/extensionHost.ts
+++ b/src/extension/extensionHost.ts
@@ -83,8 +83,8 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
     const languageFeatures = new ExtLanguageFeatures(proxy('languageFeatures'), documents)
     handleRequests(connection, 'languageFeatures', languageFeatures)
 
-    const searchFeatures = new ExtSearch(proxy('searchFeatures'))
-    handleRequests(connection, 'searchFeatures', searchFeatures)
+    const search = new ExtSearch(proxy('search'))
+    handleRequests(connection, 'search', search)
 
     const commands = new ExtCommands(proxy('commands'))
     handleRequests(connection, 'commands', commands)
@@ -134,7 +134,7 @@ function createExtensionHandle(initData: InitData, connection: Connection): type
         },
 
         search: {
-            registerQueryTransformer: provider => searchFeatures.registerQueryTransformer(provider),
+            registerQueryTransformer: provider => search.registerQueryTransformer(provider),
         },
 
         commands: {
diff --git a/src/integration-test/search.test.ts b/src/integration-test/search.test.ts
index 16ff881..cdc08df 100644
--- a/src/integration-test/search.test.ts
+++ b/src/integration-test/search.test.ts
@@ -17,7 +17,7 @@ describe('search (integration)', () => {
             'bar'
         )
 
-        // Unregister the provider and ensure it's removed
+        // Unregister the provider and ensure it's removed.
         unsubscribe.unsubscribe()
         assert.deepStrictEqual(
             await clientController.registries.queryTransformer
@@ -33,14 +33,14 @@ describe('search (integration)', () => {
 
         // Register the provider and call it
         extensionHost.search.registerQueryTransformer({ transformQuery: q => `${q} bar` })
-        extensionHost.search.registerQueryTransformer({ transformQuery: q => `${q} baz` })
+        extensionHost.search.registerQueryTransformer({ transformQuery: q => `${q} qux` })
         await ready
         assert.deepStrictEqual(
             await clientController.registries.queryTransformer
                 .transformQuery('foo')
                 .pipe(take(1))
                 .toPromise(),
-            'foo bar baz'
+            'foo bar qux'
         )
     })
 })
diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index 81ba84e..7e99c1f 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -717,14 +717,6 @@ declare module 'sourcegraph' {
         ): ProviderResult<Location[]>
     }
 
-    export interface QueryTransformerProvider {
-        transformQuery(query: string): ProviderResult<string>
-    }
-
-    export namespace search {
-        export function registerQueryTransformer(provider: QueryTransformerProvider): Unsubscribable
-    }
-
     export namespace languages {
         export function registerHoverProvider(selector: DocumentSelector, provider: HoverProvider): Unsubscribable
 
@@ -793,6 +785,38 @@ declare module 'sourcegraph' {
         ): Unsubscribable
     }
 
+    /**
+     * A query transformer changes a user's query before passing it to the search backend.
+     * Query transformers allow extensions to define new search query operators and syntax,
+     * for example, by replacing certain custom operators (e.g. `go.imports:`) with a regular expression.
+     *
+     */
+    export interface QueryTransformer {
+        /**
+         * Transforms a search query into another, valid query. If there are no transformations to be made
+         * the original query is returned.
+         *
+         * @param query A search query provided by a client.
+         */
+        transformQuery(query: string): string | Promise<string>
+    }
+
+    /**
+     * Search functionality can be augmented by extensions. Extensions can register query transformers
+     * to alter queries provided by users.
+     */
+    export namespace search {
+        /**
+         * Registers a query transformer.
+         *
+         * Multiple transformers can be registered. In that case, all transformers will be executed
+         * and the result is a single query that has been altered by all transformers.
+         *
+         * @param provider A query transformer.
+         */
+        export function registerQueryTransformer(provider: QueryTransformer): Unsubscribable
+    }
+
     /**
      * Commands are functions that are implemented and registered by extensions. Extensions can invoke any command
      * (including commands registered by other extensions). The extension can also define contributions (in

From c112fa70f3419660376fad5bdb072009b2f3e738 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 11:49:54 -0700
Subject: [PATCH 13/17] fix: remove unneeded internal tsdoc directives

---
 src/extension/api/search.ts | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index ea8863b..90f989e 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -3,12 +3,10 @@ import { QueryTransformer } from 'sourcegraph'
 import { SearchAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
-/** @internal */
 export interface ExtSearchAPI {
     $transformQuery: (id: number, query: string) => Promise<string>
 }
 
-/** @internal */
 export class ExtSearch implements ExtSearchAPI {
     private registrations = new ProviderMap<QueryTransformer>(id => this.proxy.$unregister(id))
     constructor(private proxy: SearchAPI) {}

From 61756bc2ecc91bbeba12343156d2a12294f484e3 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 13:15:49 -0700
Subject: [PATCH 14/17] fix: add string as transform query return type

---
 src/client/providers/queryTransformer.ts | 2 +-
 src/extension/api/search.ts              | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/client/providers/queryTransformer.ts b/src/client/providers/queryTransformer.ts
index ae32f24..2621cb2 100644
--- a/src/client/providers/queryTransformer.ts
+++ b/src/client/providers/queryTransformer.ts
@@ -22,7 +22,7 @@ export function transformQuery(providers: Observable<TransformQuerySignature[]>,
     return providers.pipe(
         switchMap(providers => {
             if (providers.length === 0) {
-                return [query]
+                return query
             }
             return providers.reduce(
                 (currentQuery, transformQuery) =>
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index 90f989e..13f674c 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -4,7 +4,7 @@ import { SearchAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
 export interface ExtSearchAPI {
-    $transformQuery: (id: number, query: string) => Promise<string>
+    $transformQuery: (id: number, query: string) => string | Promise<string>
 }
 
 export class ExtSearch implements ExtSearchAPI {
@@ -17,8 +17,8 @@ export class ExtSearch implements ExtSearchAPI {
         return subscription
     }
 
-    public $transformQuery(id: number, query: string): Promise<string> {
+    public $transformQuery(id: number, query: string): string | Promise<string> {
         const provider = this.registrations.get<QueryTransformer>(id)
-        return Promise.resolve(provider.transformQuery(query))
+        return provider.transformQuery(query)
     }
 }

From f1326e366f1c5538c90ae5dcbe290a4b2ddefe18 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 13:56:06 -0700
Subject: [PATCH 15/17] Revert "fix: add string as transform query return type"

This reverts commit 61756bc2ecc91bbeba12343156d2a12294f484e3.
---
 src/client/providers/queryTransformer.ts | 2 +-
 src/extension/api/search.ts              | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/client/providers/queryTransformer.ts b/src/client/providers/queryTransformer.ts
index 2621cb2..ae32f24 100644
--- a/src/client/providers/queryTransformer.ts
+++ b/src/client/providers/queryTransformer.ts
@@ -22,7 +22,7 @@ export function transformQuery(providers: Observable<TransformQuerySignature[]>,
     return providers.pipe(
         switchMap(providers => {
             if (providers.length === 0) {
-                return query
+                return [query]
             }
             return providers.reduce(
                 (currentQuery, transformQuery) =>
diff --git a/src/extension/api/search.ts b/src/extension/api/search.ts
index 13f674c..90f989e 100644
--- a/src/extension/api/search.ts
+++ b/src/extension/api/search.ts
@@ -4,7 +4,7 @@ import { SearchAPI } from 'src/client/api/search'
 import { ProviderMap } from './common'
 
 export interface ExtSearchAPI {
-    $transformQuery: (id: number, query: string) => string | Promise<string>
+    $transformQuery: (id: number, query: string) => Promise<string>
 }
 
 export class ExtSearch implements ExtSearchAPI {
@@ -17,8 +17,8 @@ export class ExtSearch implements ExtSearchAPI {
         return subscription
     }
 
-    public $transformQuery(id: number, query: string): string | Promise<string> {
+    public $transformQuery(id: number, query: string): Promise<string> {
         const provider = this.registrations.get<QueryTransformer>(id)
-        return provider.transformQuery(query)
+        return Promise.resolve(provider.transformQuery(query))
     }
 }

From 480071bdaf81463b8890b956cb26b8cd8c25e696 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 14:46:57 -0700
Subject: [PATCH 16/17] fix: update docs

---
 src/sourcegraph.d.ts | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index 7e99c1f..258dc89 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -786,10 +786,10 @@ declare module 'sourcegraph' {
     }
 
     /**
-     * A query transformer changes a user's query before passing it to the search backend.
-     * Query transformers allow extensions to define new search query operators and syntax,
-     * for example, by replacing certain custom operators (e.g. `go.imports:`) with a regular expression.
+     * A query transformer alters a user's search query before executing a search.
      *
+     * Query transformers allow extensions to define new search query operators and syntax, for example,
+     * by matching strings in a query (e.g. `go.imports:`) and replacing them with a regular expression or string.
      */
     export interface QueryTransformer {
         /**
@@ -802,8 +802,7 @@ declare module 'sourcegraph' {
     }
 
     /**
-     * Search functionality can be augmented by extensions. Extensions can register query transformers
-     * to alter queries provided by users.
+     * API for extensions to augment search functionality.
      */
     export namespace search {
         /**

From 4c57caee474fff019d621f7a86b1fb7edd31ed33 Mon Sep 17 00:00:00 2001
From: Farhan Attamimi <farhan@sourcegraph.com>
Date: Fri, 26 Oct 2018 14:56:36 -0700
Subject: [PATCH 17/17] fix: docs

---
 src/sourcegraph.d.ts | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/sourcegraph.d.ts b/src/sourcegraph.d.ts
index 258dc89..097ccf2 100644
--- a/src/sourcegraph.d.ts
+++ b/src/sourcegraph.d.ts
@@ -796,7 +796,7 @@ declare module 'sourcegraph' {
          * Transforms a search query into another, valid query. If there are no transformations to be made
          * the original query is returned.
          *
-         * @param query A search query provided by a client.
+         * @param query A search query.
          */
         transformQuery(query: string): string | Promise<string>
     }
@@ -808,8 +808,9 @@ declare module 'sourcegraph' {
         /**
          * Registers a query transformer.
          *
-         * Multiple transformers can be registered. In that case, all transformers will be executed
-         * and the result is a single query that has been altered by all transformers.
+         * Multiple transformers can be registered. In that case, all transformations will be applied
+         * and the result is a single query that has been altered by all transformers. The order in
+         * which transfomers are applied is not defined.
          *
          * @param provider A query transformer.
          */