[refactor] Move sourcemapping logic to dedicated file (#81310)

Resolves #81231 (comment)

Author: eps1lon

package.json

@@ -305,7 +305,8 @@
     "patchedDependencies": {
       "[email protected]": "patches/[email protected]",
       "[email protected]": "patches/[email protected]",
-      "@ampproject/[email protected]": "patches/@[email protected]"
+      "@ampproject/[email protected]": "patches/@[email protected]",
+      "@types/[email protected]": "patches/@[email protected]"
     }
   }
 }

packages/next/src/server/dev/hot-reloader-turbopack.ts

@@ -77,12 +77,10 @@ import { FAST_REFRESH_RUNTIME_RELOAD } from './messages'
 import { generateEncryptionKeyBase64 } from '../app-render/encryption-utils-server'
 import { isAppPageRouteDefinition } from '../route-definitions/app-page-route-definition'
 import { normalizeAppPath } from '../../shared/lib/router/utils/app-paths'
+import type { ModernSourceMapPayload } from '../lib/source-maps'
 import { getNodeDebugType } from '../lib/utils'
 import { isMetadataRouteFile } from '../../lib/metadata/is-metadata-route'
-import {
-  setBundlerFindSourceMapImplementation,
-  type ModernSourceMapPayload,
-} from '../patch-error-inspect'
+import { setBundlerFindSourceMapImplementation } from '../patch-error-inspect'
 import { getNextErrorFeedbackMiddleware } from '../../next-devtools/server/get-next-error-feedback-middleware'
 import {
   formatIssue,

packages/next/src/server/dev/middleware-turbopack.ts

@@ -12,12 +12,15 @@ import { openFileInEditor } from '../../next-devtools/server/launch-editor'
 import type { StackFrame } from 'next/dist/compiled/stacktrace-parser'
 import {
   SourceMapConsumer,
-  type BasicSourceMapConsumer,
   type NullableMappedPosition,
 } from 'next/dist/compiled/source-map08'
 import type { Project, TurbopackStackFrame } from '../../build/swc/types'
+import {
+  type ModernSourceMapPayload,
+  findApplicableSourceMapPayload,
+} from '../lib/source-maps'
 import { getSourceMapFromFile } from './get-source-map-from-file'
-import { findSourceMap, type SourceMapPayload } from 'node:module'
+import { findSourceMap } from 'node:module'
 import { pathToFileURL } from 'node:url'
 import { inspect } from 'node:util'
 
@@ -170,61 +173,6 @@ function createStackFrame(
   } satisfies TurbopackStackFrame
 }
 
-/**
- * https://tc39.es/source-map/#index-map
- */
-interface IndexSourceMapSection {
-  offset: {
-    line: number
-    column: number
-  }
-  map: ModernRawSourceMap
-}
-
-// TODO(veil): Upstream types
-interface IndexSourceMap {
-  version: number
-  file: string
-  sections: IndexSourceMapSection[]
-}
-
-interface ModernRawSourceMap extends SourceMapPayload {
-  ignoreList?: number[]
-}
-
-type ModernSourceMapPayload = ModernRawSourceMap | IndexSourceMap
-
-/**
- * Finds the sourcemap payload applicable to a given frame.
- * Equal to the input unless an Index Source Map is used.
- */
-function findApplicableSourceMapPayload(
-  frame: TurbopackStackFrame,
-  payload: ModernSourceMapPayload
-): ModernRawSourceMap | undefined {
-  if ('sections' in payload) {
-    const frameLine = frame.line ?? 0
-    const frameColumn = frame.column ?? 0
-    // Sections must not overlap and must be sorted: https://tc39.es/source-map/#section-object
-    // Therefore the last section that has an offset less than or equal to the frame is the applicable one.
-    // TODO(veil): Binary search
-    let section: IndexSourceMapSection | undefined = payload.sections[0]
-    for (
-      let i = 0;
-      i < payload.sections.length &&
-      payload.sections[i].offset.line <= frameLine &&
-      payload.sections[i].offset.column <= frameColumn;
-      i++
-    ) {
-      section = payload.sections[i]
-    }
-
-    return section === undefined ? undefined : section.map
-  } else {
-    return payload
-  }
-}
-
 /**
  * @returns 1-based lines and 0-based columns
  */
@@ -244,7 +192,7 @@ async function nativeTraceSource(
   }
 
   if (sourceMapPayload !== undefined) {
-    let consumer: BasicSourceMapConsumer
+    let consumer: SourceMapConsumer
     try {
       consumer = await new SourceMapConsumer(sourceMapPayload)
     } catch (cause) {
@@ -282,7 +230,8 @@ async function nativeTraceSource(
     if (traced !== null) {
       const { originalPosition, sourceContent } = traced
       const applicableSourceMap = findApplicableSourceMapPayload(
-        frame,
+        frame.line ?? 0,
+        frame.column ?? 0,
         sourceMapPayload
       )
 

packages/next/src/server/dev/middleware-webpack.ts

@@ -1,12 +1,13 @@
 import { findSourceMap, type SourceMap } from 'module'
 import path from 'path'
 import { fileURLToPath, pathToFileURL } from 'url'
-import {
-  SourceMapConsumer,
-  type BasicSourceMapConsumer,
-} from 'next/dist/compiled/source-map08'
+import { SourceMapConsumer } from 'next/dist/compiled/source-map08'
 import type { StackFrame } from 'next/dist/compiled/stacktrace-parser'
 import { getSourceMapFromFile } from './get-source-map-from-file'
+import {
+  sourceMapIgnoreListsEverything,
+  type ModernSourceMapPayload,
+} from '../lib/source-maps'
 import { openFileInEditor } from '../../next-devtools/server/launch-editor'
 import {
   getOriginalCodeFrame,
@@ -15,7 +16,6 @@ import {
   type OriginalStackFramesResponse,
 } from '../../next-devtools/server/shared'
 import { middlewareResponse } from '../../next-devtools/server/middleware-response'
-export { getSourceMapFromFile }
 
 import type { IncomingMessage, ServerResponse } from 'http'
 import type webpack from 'webpack'
@@ -50,13 +50,13 @@ type SourceAttributes = {
 type Source =
   | {
       type: 'file'
-      sourceMap: RawSourceMap
+      sourceMap: ModernSourceMapPayload
       ignoredSources: IgnoredSources
       moduleURL: string
     }
   | {
       type: 'bundle'
-      sourceMap: RawSourceMap
+      sourceMap: ModernSourceMapPayload
       ignoredSources: IgnoredSources
       compilation: webpack.Compilation
       moduleId: string
@@ -87,10 +87,10 @@ function getSourcePath(source: string) {
  * @returns 1-based lines and 0-based columns
  */
 async function findOriginalSourcePositionAndContent(
-  sourceMap: RawSourceMap,
+  sourceMap: ModernSourceMapPayload,
   position: { lineNumber: number | null; column: number | null }
 ): Promise<SourceAttributes | null> {
-  let consumer: BasicSourceMapConsumer
+  let consumer: SourceMapConsumer
   try {
     consumer = await new SourceMapConsumer(sourceMap)
   } catch (cause) {
@@ -309,7 +309,11 @@ async function getSource(
     return {
       type: 'file',
       sourceMap: sourceMapPayload,
-      ignoredSources: getIgnoredSources(sourceMapPayload),
+
+      ignoredSources: getIgnoredSources(
+        // @ts-expect-error -- TODO: Support IndexSourceMap
+        sourceMapPayload
+      ),
       moduleURL: sourceURL,
     }
   }
@@ -411,12 +415,6 @@ function getOriginalStackFrames({
   )
 }
 
-function sourceMapIgnoreListsEverything(
-  sourceMap: RawSourceMap & { ignoreList?: number[] }
-): boolean {
-  return sourceMap.sources.length === sourceMap.ignoreList?.length
-}
-
 async function getOriginalStackFrame({
   isServer,
   isEdgeServer,

packages/next/src/server/lib/source-maps.ts

@@ -0,0 +1,82 @@
+/**
+ * https://tc39.es/source-map/#index-map
+ */
+interface IndexSourceMapSection {
+  offset: {
+    line: number
+    column: number
+  }
+  map: BasicSourceMapPayload
+}
+
+// TODO(veil): Upstream types
+/** https://tc39.es/ecma426/#sec-index-source-map */
+interface IndexSourceMap {
+  version: number
+  file: string
+  sections: IndexSourceMapSection[]
+}
+
+/** https://tc39.es/ecma426/#sec-source-map-format */
+interface BasicSourceMapPayload {
+  version: number
+  // TODO: Move to https://github.com/jridgewell/sourcemaps which is actively maintained
+  /** WARNING: `file` is optional. */
+  file: string
+  sourceRoot?: string
+  // TODO: Move to https://github.com/jridgewell/sourcemaps which is actively maintained
+  /** WARNING: `sources[number]` can be `null`. */
+  sources: Array<string>
+  names: Array<string>
+  mappings: string
+  ignoreList?: number[]
+}
+
+export type ModernSourceMapPayload = BasicSourceMapPayload | IndexSourceMap
+
+// TODO: This should take the BasicSourceMapPayload. Only the relevant section
+// needs to ignore list everything making this check effectively O(1) multiplied
+// by the complexity of finding the section.
+export function sourceMapIgnoreListsEverything(
+  sourceMap: ModernSourceMapPayload
+): boolean {
+  if ('sections' in sourceMap) {
+    return sourceMap.sections.every((section) => {
+      return sourceMapIgnoreListsEverything(section.map)
+    })
+  }
+  return (
+    sourceMap.ignoreList !== undefined &&
+    sourceMap.sources.length === sourceMap.ignoreList.length
+  )
+}
+
+/**
+ * Finds the sourcemap payload applicable to a given frame.
+ * Equal to the input unless an Index Source Map is used.
+ */
+export function findApplicableSourceMapPayload(
+  lineNumber: number,
+  columnNumber: number,
+  payload: ModernSourceMapPayload
+): BasicSourceMapPayload | undefined {
+  if ('sections' in payload) {
+    // Sections must not overlap and must be sorted: https://tc39.es/source-map/#section-object
+    // Therefore the last section that has an offset less than or equal to the frame is the applicable one.
+    // TODO(veil): Binary search
+    let section: IndexSourceMapSection | undefined = payload.sections[0]
+    for (
+      let i = 0;
+      i < payload.sections.length &&
+      payload.sections[i].offset.line <= lineNumber &&
+      payload.sections[i].offset.column <= columnNumber;
+      i++
+    ) {
+      section = payload.sections[i]
+    }
+
+    return section === undefined ? undefined : section.map
+  } else {
+    return payload
+  }
+}