fix(debugger): address TS errors (#6966)

Address a large majority of the TS type errors in the debugger code. The
only actual change to the runtime logic is the following:

When adding a new breakpoint to a file that has a source map, we now
validate that the generated position can be identified. If not, we abort
and don't add the breakpoint (which most likely would have failed
anyway). An error will be sent to the debugger diagnostics endpoint if
that happens.

Another minor, but hopefully invisible change, is that all private
fields in the `JSONBuffer` class are now properly private instead of
just being prefixed with an underscore.

The only debugger TS errors not addressed in this commit are the following:
- The ones already addressed in #6965
- The ones which will disappear once
  #6951 lands

This commit also adds a `tsconfig.debugger.json` file, which can be used
to check the types of the debugger code:

    ./node_modules/.bin/tsc --noEmit -p tsconfig.debugger.json

Author: watson

integration-tests/debugger/basic.spec.js

@@ -124,7 +124,11 @@ describe('Dynamic Instrumentation', function () {
             const expected = expectedPayloads.shift()
             assertObjectContains(event, expected)
             assertUUID(event.debugger.diagnostics.runtimeId)
-            if (event.debugger.diagnostics.status === 'INSTALLED') triggers.shift()()
+            if (event.debugger.diagnostics.status === 'INSTALLED') {
+              const trigger = triggers.shift()
+              assert.ok(trigger, 'expecting a trigger function to be defined')
+              trigger()
+            }
             endIfDone()
           })
         })
@@ -195,12 +199,14 @@ describe('Dynamic Instrumentation', function () {
 
       it(
         'should send expected error diagnostics messages if probe type isn\'t supported',
+        // @ts-expect-error Expecting this probe type to be invalid
         unsupporedOrInvalidProbesTest(t.generateProbeConfig({ type: 'INVALID_PROBE' }))
       )
 
       it(
         'should send expected error diagnostics messages if it isn\'t a line-probe',
         unsupporedOrInvalidProbesTest(
+          // @ts-expect-error Expecting this probe type to be invalid
           t.generateProbeConfig({ where: { typeName: 'index.js', methodName: 'handlerA' } })
         )
       )
@@ -513,7 +519,11 @@ describe('Dynamic Instrumentation', function () {
 
         t.agent.on('debugger-diagnostics', ({ payload }) => {
           payload.forEach((event) => {
-            if (event.debugger.diagnostics.status === 'INSTALLED') triggers.shift()().catch(done)
+            if (event.debugger.diagnostics.status === 'INSTALLED') {
+              const trigger = triggers.shift()
+              assert.ok(trigger, 'expecting a trigger function to be defined')
+              trigger().catch(done)
+            }
           })
         })
 
@@ -587,6 +597,12 @@ describe('Dynamic Instrumentation', function () {
       })
 
       it('should adhere to individual probes sample rate', function (done) {
+        /** @type {(() => void) & { calledOnce?: boolean }} */
+        const doneWhenCalledTwice = () => {
+          if (doneWhenCalledTwice.calledOnce) return done()
+          doneWhenCalledTwice.calledOnce = true
+        }
+
         const rcConfig1 = t.breakpoints[0].generateRemoteConfig({ sampling: { snapshotsPerSecond: 1 } })
         const rcConfig2 = t.breakpoints[1].generateRemoteConfig({ sampling: { snapshotsPerSecond: 1 } })
         const state = {
@@ -632,11 +648,6 @@ describe('Dynamic Instrumentation', function () {
 
         t.agent.addRemoteConfig(rcConfig1)
         t.agent.addRemoteConfig(rcConfig2)
-
-        function doneWhenCalledTwice () {
-          if (doneWhenCalledTwice.calledOnce) return done()
-          doneWhenCalledTwice.calledOnce = true
-        }
       })
     })
 

integration-tests/debugger/target-app/basic.js

@@ -1,6 +1,7 @@
 'use strict'
 
 require('dd-trace/init')
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/target-app/redact.js

@@ -1,6 +1,7 @@
 'use strict'
 
 require('dd-trace/init')
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/target-app/snapshot-pruning.js

@@ -3,6 +3,7 @@
 require('dd-trace/init')
 
 const { randomBytes } = require('crypto')
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/target-app/snapshot-time-budget.js

@@ -2,6 +2,7 @@
 
 require('dd-trace/init')
 
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/target-app/snapshot.js

@@ -1,6 +1,7 @@
 'use strict'
 
 require('dd-trace/init')
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/target-app/template.js

@@ -2,6 +2,7 @@
 
 require('dd-trace/init')
 const { inspect } = require('util')
+// @ts-expect-error This code is running in a sandbox where fastify is available
 const Fastify = require('fastify')
 
 const fastify = Fastify({ logger: { level: 'error' } })

integration-tests/debugger/utils.js

@@ -22,6 +22,12 @@ const pollInterval = 0.1
  *   GenerateProbeConfigFn
  */
 
+/**
+ * Bound version of generateProbeConfig that only requires optional overrides (breakpoint is already bound).
+ *
+ * @typedef {(overrides?: Partial<ProbeConfig>) => ProbeConfig} BoundGenerateProbeConfigFn
+ */
+
 /**
  * @typedef {Object} BreakpointInfo
  * @property {string} sourceFile
@@ -37,7 +43,7 @@ const pollInterval = 0.1
  *   rcConfig: object|null,
  *   triggerBreakpoint: (url: string) => Promise<import('axios').AxiosResponse<unknown>>,
  *   generateRemoteConfig: (overrides?: object) => object,
- *   generateProbeConfig: GenerateProbeConfigFn
+ *   generateProbeConfig: BoundGenerateProbeConfigFn
  * }} EnrichedBreakpoint
  */
 
@@ -59,7 +65,7 @@ const pollInterval = 0.1
  * @property {() => Promise<import('axios').AxiosResponse<unknown>>} triggerBreakpoint - Triggers the primary breakpoint
  *   once installed.
  * @property {(overrides?: object) => object} generateRemoteConfig - Generates RC for the primary breakpoint.
- * @property {GenerateProbeConfigFn} generateProbeConfig - Generates probe config for the primary breakpoint.
+ * @property {BoundGenerateProbeConfigFn} generateProbeConfig - Generates probe config for the primary breakpoint.
  */
 
 module.exports = {

packages/dd-trace/src/debugger/devtools_client/breakpoints.js

@@ -80,8 +80,17 @@ async function addBreakpoint (probe) {
     log.debug(
       '[debugger:devtools_client] Translating location using source map for %s:%d:%d (probe: %s, version: %d)',
       file, lineNumber, columnNumber, probe.id, probe.version
-    );
-    ({ line: lineNumber, column: columnNumber } = await getGeneratedPosition(url, source, lineNumber, sourceMapURL))
+    )
+    const position = await getGeneratedPosition(url, source, lineNumber, sourceMapURL)
+    if (position.line !== null && position.column !== null) {
+      lineNumber = position.line
+      columnNumber = position.column
+    } else {
+      throw new Error(
+        // eslint-disable-next-line @stylistic/max-len
+        `Could not find generated position for ${url}:${lineNumber}:${columnNumber} (probe: ${probe.id}, version: ${probe.version})`
+      )
+    }
   }
 
   try {

packages/dd-trace/src/debugger/devtools_client/index.js

@@ -46,6 +46,7 @@ let snapshotProbeIndexBuffer, snapshotProbeIndex
 
 if (SUPPORT_ARRAY_BUFFER_RESIZE) {
   // TODO: Is a limit of 256 snapshots ever going to be a problem?
+  // @ts-ignore - ArrayBuffer constructor with maxByteLength is available in Node.js 20+ but not in @types/node@18
   // eslint-disable-next-line n/no-unsupported-features/es-syntax
   snapshotProbeIndexBuffer = new ArrayBuffer(1, { maxByteLength: 256 })
   // TODO: Is a limit of 256 probes ever going to be a problem?