feat(server): rethrow handler plugin

apps/content/.vitepress/config.ts

@@ -150,6 +150,7 @@ export default withMermaid(defineConfig({
             { text: 'Batch Requests', link: '/docs/plugins/batch-requests' },
             { text: 'Client Retry', link: '/docs/plugins/client-retry' },
             { text: 'Retry After', link: '/docs/plugins/retry-after' },
+            { text: 'Rethrow Handler', link: '/docs/plugins/rethrow-handler' },
             { text: 'Compression', link: '/docs/plugins/compression' },
             { text: 'Body Limit', link: '/docs/plugins/body-limit' },
             { text: 'Simple CSRF Protection', link: '/docs/plugins/simple-csrf-protection' },

apps/content/docs/openapi/integrations/implement-contract-in-nest.md

@@ -222,8 +222,11 @@ Configure the `@orpc/nest` module by importing `ORPCModule` in your NestJS appli
 ```ts
 import { Module } from '@nestjs/common'
 import { REQUEST } from '@nestjs/core'
-import { onError, ORPCModule } from '@orpc/nest'
+import { onError, ORPCError, ORPCModule } from '@orpc/nest'
 import { Request } from 'express' // if you use express adapter
+import {
+  experimental_RethrowHandlerPlugin as RethrowHandlerPlugin,
+} from '@orpc/server/plugins'
 
 declare module '@orpc/nest' {
   /**
@@ -246,7 +249,15 @@ declare module '@orpc/nest' {
         context: { request }, // oRPC context, accessible from middlewares, etc.
         eventIteratorKeepAliveInterval: 5000, // 5 seconds
         customJsonSerializers: [],
-        plugins: [], // most oRPC plugins are compatible
+        plugins: [
+          new RethrowHandlerPlugin({
+            filter: (error) => {
+              // Rethrow all non-ORPCError errors
+              // This allows unhandled exceptions to bubble up to NestJS global exception filters
+              return !(error instanceof ORPCError)
+            },
+          })
+        ], // most oRPC plugins are compatible
       }),
       inject: [REQUEST],
     }),

apps/content/docs/plugins/rethrow-handler.md

@@ -0,0 +1,38 @@
+---
+title: Rethrow Handler Plugin
+description: A plugin to catch and rethrow specific errors during request handling instead of handling them in the oRPC error flow.
+---
+
+# Rethrow Handler Plugin
+
+The `RethrowHandlerPlugin` allows you to catch and rethrow specific errors that occur during request handling. This is particularly useful when your framework has its own error handling mechanism (e.g., global exception filters in NestJS, error middleware in Express) and you want certain errors to be processed by that mechanism instead of being handled by the oRPC error handling flow.
+
+## Usage
+
+```ts twoslash
+import { ORPCError } from '@orpc/server'
+import { RPCHandler } from '@orpc/server/fetch'
+import { router } from './shared/planet'
+
+// ---cut---
+import {
+  experimental_RethrowHandlerPlugin as RethrowHandlerPlugin,
+} from '@orpc/server/plugins'
+
+const handler = new RPCHandler(router, {
+  plugins: [
+    new RethrowHandlerPlugin({
+      // Decide which errors should be rethrown.
+      filter: (error) => {
+        // Example: Rethrow all non-ORPCError errors
+        // This allows unhandled exceptions to bubble up to your framework
+        return !(error instanceof ORPCError)
+      },
+    }),
+  ],
+})
+```
+
+::: info
+The `handler` can be any supported oRPC handler, such as [RPCHandler](/docs/rpc-handler), [OpenAPIHandler](/docs/openapi/openapi-handler), or another custom handler.
+:::

packages/server/src/plugins/index.ts

@@ -2,5 +2,6 @@ export * from './batch'
 export * from './cors'
 export * from './request-headers'
 export * from './response-headers'
+export * from './rethrow'
 export * from './simple-csrf-protection'
 export * from './strict-get-method'

packages/server/src/plugins/rethrow.test.ts

@@ -0,0 +1,195 @@
+import { ORPCError } from '@orpc/client'
+import { RPCHandler } from '../adapters/fetch'
+import { os } from '../builder'
+import { experimental_RethrowHandlerPlugin as RethrowHandlerPlugin } from './rethrow'
+
+beforeEach(() => {
+  vi.clearAllMocks()
+})
+
+describe('rethrowHandlerPlugin', () => {
+  it('should rethrow errors when filter returns true', async () => {
+    class CustomError extends Error {
+      constructor(message: string, public readonly code: number) {
+        super(message)
+        this.name = 'CustomError'
+      }
+    }
+
+    const customError = new CustomError('Error with code', 42)
+
+    const handler = new RPCHandler({
+      ping: os.handler(() => {
+        throw customError
+      }),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({
+          filter: () => true, // Always rethrow
+        }),
+      ],
+    })
+
+    await expect(
+      handler.handle(new Request('http://localhost/ping', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).rejects.toThrow(customError)
+  })
+
+  it('should not rethrow errors when filter returns false', async () => {
+    const customError = new Error('Custom error that should not be rethrown')
+
+    const handler = new RPCHandler({
+      ping: os.handler(() => {
+        throw customError
+      }),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({
+          filter: () => false, // Never rethrow
+        }),
+      ],
+    })
+
+    await expect(
+      handler.handle(new Request('http://localhost/ping', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).resolves.toEqual({ matched: true, response: expect.toSatisfy((response: Response) => response.status === 500) })
+  })
+
+  it('should rethrow non-ORPCError errors and handle ORPCError normally', async () => {
+    const handler = new RPCHandler({
+      throwCustom: os.handler(() => {
+        throw new Error('Custom error')
+      }),
+      throwORPC: os.handler(() => {
+        throw new ORPCError('BAD_REQUEST', { message: 'ORPC error' })
+      }),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({
+          filter: error => !(error instanceof ORPCError),
+        }),
+      ],
+    })
+
+    // Non-ORPCError should be rethrown
+    await expect(
+      handler.handle(new Request('http://localhost/throwCustom', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).rejects.toThrow('Custom error')
+
+    // ORPCError should be handled normally (not rethrown)
+    await expect(
+      handler.handle(new Request('http://localhost/throwORPC', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).resolves.toEqual({ matched: true, response: expect.toSatisfy((response: Response) => response.status === 400) })
+  })
+
+  it('should pass error and options to filter function', async () => {
+    const filter = vi.fn(() => false)
+    const thrownError = new Error('Test error')
+
+    const handler = new RPCHandler({
+      ping: os.handler(() => {
+        throw thrownError
+      }),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({ filter }),
+      ],
+    })
+
+    await handler.handle(new Request('http://localhost/ping', {
+      method: 'POST',
+      body: JSON.stringify({}),
+      headers: { 'Content-Type': 'application/json' },
+    }))
+
+    expect(filter).toHaveBeenCalledTimes(1)
+    expect(filter).toHaveBeenCalledWith(
+      thrownError,
+      expect.objectContaining({
+        request: expect.objectContaining({
+          method: 'POST',
+        }),
+        context: expect.any(Object),
+      }),
+    )
+  })
+
+  it('should work normally without errors being thrown', async () => {
+    const handler = new RPCHandler({
+      ping: os.handler(() => 'pong'),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({
+          filter: () => true,
+        }),
+      ],
+    })
+
+    await expect(
+      handler.handle(new Request('http://localhost/ping', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).resolves.toEqual({
+      matched: true,
+      response: expect.toSatisfy((response: Response) => response.status === 200),
+    })
+  })
+
+  it('should response error if other plugins or interceptors corrupt the context', async () => {
+    const handler = new RPCHandler({
+      ping: os.handler(() => 'pong'),
+    }, {
+      strictGetMethodPluginEnabled: false,
+      plugins: [
+        new RethrowHandlerPlugin({
+          filter: () => true,
+        }),
+        {
+          init(options) {
+            options.rootInterceptors?.push(async (options) => {
+              // Corrupt the context
+              return options.next({
+                ...options,
+                context: {},
+              })
+            })
+          },
+        },
+      ],
+    })
+
+    await expect(
+      handler.handle(new Request('http://localhost/ping', {
+        method: 'POST',
+        body: JSON.stringify({}),
+        headers: { 'Content-Type': 'application/json' },
+      })),
+    ).resolves.toEqual({
+      matched: true,
+      response: expect.toSatisfy((response: Response) => response.status === 500),
+    })
+  })
+})

packages/server/src/plugins/rethrow.ts

@@ -0,0 +1,88 @@
+import type { ThrowableError, Value } from '@orpc/shared'
+import type { StandardHandlerInterceptorOptions, StandardHandlerOptions, StandardHandlerPlugin } from '../adapters/standard'
+import type { Context } from '../context'
+import { value } from '@orpc/shared'
+
+export interface experimental_RethrowHandlerPluginOptions<T extends Context> {
+  /**
+   * Decide which errors should be rethrown.
+   *
+   * @example
+   * ```ts
+   * const rethrowPlugin = new RethrowHandlerPlugin({
+   *   filter: (error) => {
+   *     // Rethrow all non-ORPCError errors
+   *     return !(error instanceof ORPCError)
+   *   }
+   * })
+   * ```
+   */
+  filter: Value<boolean, [error: ThrowableError, options: StandardHandlerInterceptorOptions<T>]>
+}
+
+interface RethrowHandlerPluginContext {
+  error?: { value: ThrowableError }
+}
+
+/**
+ * The plugin allows you to catch and rethrow specific errors that occur during request handling.
+ * This is particularly useful when your framework has its own error handling mechanism
+ * (e.g., global exception filters in NestJS, error middleware in Express)
+ * and you want certain errors to be processed by that mechanism instead of being handled by the
+ * oRPC error handling flow.
+ *
+ * @see {@link https://orpc.dev/docs/plugins/rethrow-handler Rethrow Handler Plugin Docs}
+ */
+export class experimental_RethrowHandlerPlugin<T extends Context> implements StandardHandlerPlugin<T> {
+  private readonly filter: experimental_RethrowHandlerPluginOptions<T>['filter']
+
+  CONTEXT_SYMBOL = Symbol('ORPC_RETHROW_HANDLER_PLUGIN_CONTEXT')
+
+  constructor(options: experimental_RethrowHandlerPluginOptions<T>) {
+    this.filter = options.filter
+  }
+
+  init(options: StandardHandlerOptions<T>): void {
+    options.rootInterceptors ??= []
+    options.interceptors ??= []
+
+    options.rootInterceptors.push(async (options) => {
+      const pluginContext: RethrowHandlerPluginContext = {}
+
+      const result = await options.next({
+        ...options,
+        context: {
+          ...options.context,
+          [this.CONTEXT_SYMBOL]: pluginContext,
+        },
+      })
+
+      if (pluginContext.error) {
+        throw pluginContext.error.value
+      }
+
+      return result
+    })
+
+    options.interceptors.unshift(async (options) => {
+      const pluginContext = options.context[this.CONTEXT_SYMBOL] as RethrowHandlerPluginContext | undefined
+
+      if (!pluginContext) {
+        throw new TypeError('[RethrowHandlerPlugin] Rethrow handler context has been corrupted or modified by another plugin or interceptor')
+      }
+
+      try {
+        // await is important here to catch both sync and async errors
+        return await options.next()
+      }
+      catch (error) {
+        if (value(this.filter, error as ThrowableError, options)) {
+          pluginContext.error = { value: error as ThrowableError }
+          return { matched: false, response: undefined }
+        }
+
+        throw error
+      }
+    })
+  }
+}