[source-map] Refactor away 'sourceMapToSourceList' weak map

The 'sourceMapToSourceList' maps from source map objects to a list of
sourceURLs which that source map contains. This is also useful when
dealing with index source maps.

Unfortunately this doesn't play nicely when resolving "sourceIndices"
from mappings, since you'd first have to resolve the raw source map
object, before you could resolve the full index.

This CL cleans this up by getting rid of the weak map alltogether:
We store the 'SourceInfo' objects in a plain array, indexed by the
"sourceIndex". For index maps, we simply concatenate all the sources
in the order of the "child source maps".

To preserve the existing behavior (and fast access), we also map
the 'sourceURL' to SourceInfo object in a separate map. If a source
map contains multiple 'sources' entries that resolve to the same
URL, then the first one wins. Same as the old implementation.

[email protected]

Bug: 390337576
Change-Id: I2ae7c6b3d0667b98390085eb949cdee52375ef7f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6180299
Reviewed-by: Kim-Anh Tran <[email protected]>
Commit-Queue: Simon Zünd <[email protected]>

Author: szuend

front_end/core/sdk/SourceMap.ts

@@ -174,9 +174,8 @@ class ScopeTreeEntry implements ScopeEntry {
   }
 }
 
-const sourceMapToSourceList = new WeakMap<SourceMapV3, Platform.DevToolsPath.UrlString[]>();
-
 interface SourceInfo {
+  sourceURL: Platform.DevToolsPath.UrlString;
   content: string|null;
   ignoreListHint: boolean;
   reverseMappings: number[]|null;
@@ -189,7 +188,9 @@ export class SourceMap {
   readonly #sourceMappingURL: Platform.DevToolsPath.UrlString;
   readonly #baseURL: Platform.DevToolsPath.UrlString;
   #mappingsInternal: SourceMapEntry[]|null;
-  readonly #sourceInfos: Map<Platform.DevToolsPath.UrlString, SourceInfo>;
+
+  readonly #sourceInfos: SourceInfo[] = [];
+  readonly #sourceInfoByURL = new Map<Platform.DevToolsPath.UrlString, SourceInfo>();
 
   #scopesInfo: SourceMapScopesInfo|null = null;
 
@@ -206,7 +207,6 @@ export class SourceMap {
     this.#baseURL = (Common.ParsedURL.schemeIs(sourceMappingURL, 'data:')) ? compiledURL : sourceMappingURL;
 
     this.#mappingsInternal = null;
-    this.#sourceInfos = new Map();
     if ('sections' in this.#json) {
       if (this.#json.sections.find(section => 'url' in section)) {
         Common.Console.Console.instance().warn(
@@ -225,11 +225,11 @@ export class SourceMap {
   }
 
   sourceURLs(): Platform.DevToolsPath.UrlString[] {
-    return [...this.#sourceInfos.keys()];
+    return [...this.#sourceInfoByURL.keys()];
   }
 
   embeddedContentByURL(sourceURL: Platform.DevToolsPath.UrlString): string|null {
-    const entry = this.#sourceInfos.get(sourceURL);
+    const entry = this.#sourceInfoByURL.get(sourceURL);
     if (!entry) {
       return null;
     }
@@ -404,7 +404,7 @@ export class SourceMap {
 
   private reversedMappings(sourceURL: Platform.DevToolsPath.UrlString): number[] {
     this.#ensureMappingsProcessed();
-    return this.#sourceInfos.get(sourceURL)?.reverseMappings ?? [];
+    return this.#sourceInfoByURL.get(sourceURL)?.reverseMappings ?? [];
   }
 
   #ensureMappingsProcessed(): void {
@@ -441,7 +441,7 @@ export class SourceMap {
     }
 
     for (const [url, reverseMap] of reverseMappingsPerUrl.entries()) {
-      const info = this.#sourceInfos.get(url);
+      const info = this.#sourceInfoByURL.get(url);
       if (!info) {
         continue;
       }
@@ -475,7 +475,6 @@ export class SourceMap {
   }
 
   private parseSources(sourceMap: SourceMapV3Object): void {
-    const sourcesList = [];
     const sourceRoot = sourceMap.sourceRoot ?? '';
     const ignoreList = new Set(sourceMap.ignoreList ?? sourceMap.x_google_ignoreList);
     for (let i = 0; i < sourceMap.sources.length; ++i) {
@@ -495,31 +494,28 @@ export class SourceMap {
       const url =
           Common.ParsedURL.ParsedURL.completeURL(this.#baseURL, href) || (href as Platform.DevToolsPath.UrlString);
       const source = sourceMap.sourcesContent && sourceMap.sourcesContent[i];
-      sourcesList.push(url);
-      if (!this.#sourceInfos.has(url)) {
-        const content = source ?? null;
-        const ignoreListHint = ignoreList.has(i);
-        this.#sourceInfos.set(url, {content, ignoreListHint, reverseMappings: null, scopeTree: null});
+      const sourceInfo: SourceInfo = {
+        sourceURL: url,
+        content: source ?? null,
+        ignoreListHint: ignoreList.has(i),
+        reverseMappings: null,
+        scopeTree: null,
+      };
+      this.#sourceInfos.push(sourceInfo);
+      if (!this.#sourceInfoByURL.has(url)) {
+        this.#sourceInfoByURL.set(url, sourceInfo);
       }
     }
-    sourceMapToSourceList.set(sourceMap, sourcesList);
   }
 
   private parseMap(map: SourceMapV3Object, baseSourceIndex: number, lineNumber: number, columnNumber: number): void {
-    let sourceIndex = 0;
+    let sourceIndex = baseSourceIndex;
     let sourceLineNumber = 0;
     let sourceColumnNumber = 0;
     let nameIndex = 0;
-    // TODO(crbug.com/1011811): refactor away map.
-    // `sources` can be undefined if it wasn't previously
-    // processed and added to the list. However, that
-    // is not WAI and we should make sure that we can
-    // only reach this point when we are certain
-    // we have the list available.
-    const sources = sourceMapToSourceList.get(map);
     const names = map.names ?? [];
     const tokenIter = new TokenIterator(map.mappings);
-    let sourceURL: Platform.DevToolsPath.UrlString|undefined = sources && sources[sourceIndex];
+    let sourceURL: Platform.DevToolsPath.UrlString = this.#sourceInfos[sourceIndex].sourceURL;
 
     while (true) {
       if (tokenIter.peek() === ',') {
@@ -544,50 +540,40 @@ export class SourceMap {
       const sourceIndexDelta = tokenIter.nextVLQ();
       if (sourceIndexDelta) {
         sourceIndex += sourceIndexDelta;
-        if (sources) {
-          sourceURL = sources[sourceIndex];
-        }
+        sourceURL = this.#sourceInfos[sourceIndex].sourceURL;
       }
       sourceLineNumber += tokenIter.nextVLQ();
       sourceColumnNumber += tokenIter.nextVLQ();
 
       if (!tokenIter.hasNext() || this.isSeparator(tokenIter.peek())) {
-        this.mappings().push(new SourceMapEntry(
-            lineNumber, columnNumber, baseSourceIndex + sourceIndex, sourceURL, sourceLineNumber, sourceColumnNumber));
+        this.mappings().push(
+            new SourceMapEntry(lineNumber, columnNumber, sourceIndex, sourceURL, sourceLineNumber, sourceColumnNumber));
         continue;
       }
 
       nameIndex += tokenIter.nextVLQ();
       this.mappings().push(new SourceMapEntry(
-          lineNumber, columnNumber, baseSourceIndex + sourceIndex, sourceURL, sourceLineNumber, sourceColumnNumber,
-          names[nameIndex]));
+          lineNumber, columnNumber, sourceIndex, sourceURL, sourceLineNumber, sourceColumnNumber, names[nameIndex]));
     }
 
     if (Root.Runtime.experiments.isEnabled(Root.Runtime.ExperimentName.USE_SOURCE_MAP_SCOPES)) {
-      this.parseBloombergScopes(map);
+      this.parseBloombergScopes(map, baseSourceIndex);
       this.#parseScopes(map);
     }
   }
 
-  private parseBloombergScopes(map: SourceMapV3Object): void {
+  private parseBloombergScopes(map: SourceMapV3Object, baseSourceIndex: number): void {
     if (!map.x_com_bloomberg_sourcesFunctionMappings) {
       return;
     }
-    const sources = sourceMapToSourceList.get(map);
-    if (!sources) {
-      return;
-    }
     const names = map.names ?? [];
     const scopeList = map.x_com_bloomberg_sourcesFunctionMappings;
 
-    for (let i = 0; i < sources?.length; i++) {
-      if (!scopeList[i] || !sources[i]) {
-        continue;
-      }
-      const sourceInfo = this.#sourceInfos.get(sources[i]);
-      if (!sourceInfo) {
+    for (let i = 0; i < scopeList.length; i++) {
+      if (!scopeList[i]) {
         continue;
       }
+      const sourceInfo = this.#sourceInfos[baseSourceIndex + i];
       const scopes = scopeList[i];
 
       let nameIndex = 0;
@@ -656,7 +642,7 @@ export class SourceMap {
 
   findScopeEntry(sourceURL: Platform.DevToolsPath.UrlString, sourceLineNumber: number, sourceColumnNumber: number):
       ScopeEntry|null {
-    const sourceInfo = this.#sourceInfos.get(sourceURL);
+    const sourceInfo = this.#sourceInfoByURL.get(sourceURL);
     if (!sourceInfo || !sourceInfo.scopeTree) {
       return null;
     }
@@ -766,7 +752,7 @@ export class SourceMap {
   }
 
   hasIgnoreListHint(sourceURL: Platform.DevToolsPath.UrlString): boolean {
-    return this.#sourceInfos.get(sourceURL)?.ignoreListHint ?? false;
+    return this.#sourceInfoByURL.get(sourceURL)?.ignoreListHint ?? false;
   }
 
   /**