lib: allow CJS source map cache to be reclaimed

lib/internal/modules/cjs/loader.js

@@ -1335,7 +1335,7 @@ function wrapSafe(filename, content, cjsModuleInstance, codeCache, format) {
     // Cache the source map for the module if present.
     const { sourceMapURL } = script;
     if (sourceMapURL) {
-      maybeCacheSourceMap(filename, content, this, false, undefined, sourceMapURL);
+      maybeCacheSourceMap(filename, content, cjsModuleInstance, false, undefined, sourceMapURL);
     }
 
     return {
@@ -1358,7 +1358,7 @@ function wrapSafe(filename, content, cjsModuleInstance, codeCache, format) {
 
   // Cache the source map for the module if present.
   if (result.sourceMapURL) {
-    maybeCacheSourceMap(filename, content, this, false, undefined, result.sourceMapURL);
+    maybeCacheSourceMap(filename, content, cjsModuleInstance, false, undefined, result.sourceMapURL);
   }
 
   return result;

lib/internal/modules/esm/translators.js

@@ -178,13 +178,12 @@ translators.set('module', function moduleStrategy(url, source, isMain) {
 function loadCJSModule(module, source, url, filename, isMain) {
   const compileResult = compileFunctionForCJSLoader(source, filename, isMain, false);
 
+  const { function: compiledWrapper, sourceMapURL } = compileResult;
   // Cache the source map for the cjs module if present.
-  if (compileResult.sourceMapURL) {
-    maybeCacheSourceMap(url, source, null, false, undefined, compileResult.sourceMapURL);
+  if (sourceMapURL) {
+    maybeCacheSourceMap(url, source, module, false, undefined, sourceMapURL);
   }
 
-  const compiledWrapper = compileResult.function;
-
   const cascadedLoader = require('internal/modules/esm/loader').getOrInitializeCascadedLoader();
   const __dirname = dirname(filename);
   // eslint-disable-next-line func-name-matching,func-style

lib/internal/modules/esm/utils.js

@@ -341,7 +341,7 @@ function compileSourceTextModule(url, source, cascadedLoader) {
   }
   // Cache the source map for the module if present.
   if (wrap.sourceMapURL) {
-    maybeCacheSourceMap(url, source, null, false, undefined, wrap.sourceMapURL);
+    maybeCacheSourceMap(url, source, wrap, false, undefined, wrap.sourceMapURL);
   }
   return wrap;
 }

lib/internal/source_map/prepare_stack_trace.js

@@ -114,9 +114,15 @@ function getOriginalSymbolName(sourceMap, trace, curIndex) {
   }
 }
 
-// Places a snippet of code from where the exception was originally thrown
-// above the stack trace. This logic is modeled after GetErrorSource in
-// node_errors.cc.
+/**
+ * Return a snippet of code from where the exception was originally thrown
+ * above the stack trace. This called from GetErrorSource in node_errors.cc.
+ * @param {import('internal/source_map/source_map').SourceMap} sourceMap - the source map to be used
+ * @param {string} originalSourcePath - path or url of the original source
+ * @param {number} originalLine - line number in the original source
+ * @param {number} originalColumn - column number in the original source
+ * @returns {string | undefined} - the exact line in the source content or undefined if file not found
+ */
 function getErrorSource(
   sourceMap,
   originalSourcePath,
@@ -154,6 +160,12 @@ function getErrorSource(
   return exceptionLine;
 }
 
+/**
+ * Retrieve the original source code from the source map's `sources` list or disk.
+ * @param {import('internal/source_map/source_map').SourceMap.payload} payload
+ * @param {string} originalSourcePath - path or url of the original source
+ * @returns {string | undefined} - the source content or undefined if file not found
+ */
 function getOriginalSource(payload, originalSourcePath) {
   let source;
   // payload.sources has been normalized to be an array of absolute urls.
@@ -177,6 +189,13 @@ function getOriginalSource(payload, originalSourcePath) {
   return source;
 }
 
+/**
+ * Retrieve exact line in the original source code from the source map's `sources` list or disk.
+ * @param {string} fileName - actual file name
+ * @param {number} lineNumber - actual line number
+ * @param {number} columnNumber - actual column number
+ * @returns {string | undefined} - the source content or undefined if file not found
+ */
 function getSourceMapErrorSource(fileName, lineNumber, columnNumber) {
   const sm = findSourceMap(fileName);
   if (sm === undefined) {

lib/internal/source_map/source_map_cache.js

@@ -3,7 +3,6 @@
 const {
   ArrayPrototypePush,
   JSONParse,
-  ObjectKeys,
   RegExpPrototypeExec,
   SafeMap,
   StringPrototypeCodePointAt,
@@ -25,17 +24,15 @@ const {
 } = require('internal/errors');
 const { getLazy } = require('internal/util');
 
-// Since the CJS module cache is mutable, which leads to memory leaks when
-// modules are deleted, we use a WeakMap so that the source map cache will
-// be purged automatically:
-const getCjsSourceMapCache = getLazy(() => {
-  const { IterableWeakMap } = require('internal/util/iterable_weak_map');
-  return new IterableWeakMap();
+const getModuleSourceMapCache = getLazy(() => {
+  const { SourceMapCacheMap } = require('internal/source_map/source_map_cache_map');
+  return new SourceMapCacheMap();
 });
 
-// The esm cache is not mutable, so we can use a Map without memory concerns:
-const esmSourceMapCache = new SafeMap();
-// The generated sources is not mutable, so we can use a Map without memory concerns:
+// The generated source module/script instance is not accessible, so we can use
+// a Map without memory concerns. Separate generated source entries with the module
+// source entries to avoid overriding the module source entries with arbitrary
+// source url magic comments.
 const generatedSourceMapCache = new SafeMap();
 const kLeadingProtocol = /^\w+:\/\//;
 const kSourceMappingURLMagicComment = /\/[*/]#\s+sourceMappingURL=(?<sourceMappingURL>[^\s]+)/g;
@@ -52,6 +49,10 @@ function getSourceMapsEnabled() {
   return sourceMapsEnabled;
 }
 
+/**
+ * Enables or disables source maps programmatically.
+ * @param {boolean} val
+ */
 function setSourceMapsEnabled(val) {
   validateBoolean(val, 'val');
 
@@ -72,6 +73,14 @@ function setSourceMapsEnabled(val) {
   sourceMapsEnabled = val;
 }
 
+/**
+ * Extracts the source url from the content if present. For example
+ * //# sourceURL=file:///path/to/file
+ *
+ * Read more at: https://tc39.es/source-map-spec/#linking-evald-code-to-named-generated-code
+ * @param {string} content - source content
+ * @returns {string | null} source url or null if not present
+ */
 function extractSourceURLMagicComment(content) {
   let match;
   let matchSourceURL;
@@ -90,6 +99,14 @@ function extractSourceURLMagicComment(content) {
   return sourceURL;
 }
 
+/**
+ * Extracts the source map url from the content if present. For example
+ * //# sourceMappingURL=file:///path/to/file
+ *
+ * Read more at: https://tc39.es/source-map-spec/#linking-generated-code
+ * @param {string} content - source content
+ * @returns {string | null} source map url or null if not present
+ */
 function extractSourceMapURLMagicComment(content) {
   let match;
   let lastMatch;
@@ -104,7 +121,17 @@ function extractSourceMapURLMagicComment(content) {
   return lastMatch.groups.sourceMappingURL;
 }
 
-function maybeCacheSourceMap(filename, content, cjsModuleInstance, isGeneratedSource, sourceURL, sourceMapURL) {
+/**
+ * Caches the source map if it is present in the content, with the given filename, moduleInstance, and sourceURL.
+ * @param {string} filename - the actual filename
+ * @param {string} content - the actual source content
+ * @param {import('internal/modules/cjs/loader').Module | ModuleWrap} moduleInstance - a module instance that
+ * associated with the source, once this is reclaimed, the source map entry will be removed from the cache
+ * @param {boolean} isGeneratedSource - if the source was generated and evaluated with the global eval
+ * @param {string | undefined} sourceURL - the source url
+ * @param {string | undefined} sourceMapURL - the source map url
+ */
+function maybeCacheSourceMap(filename, content, moduleInstance, isGeneratedSource, sourceURL, sourceMapURL) {
   const sourceMapsEnabled = getSourceMapsEnabled();
   if (!(process.env.NODE_V8_COVERAGE || sourceMapsEnabled)) return;
   const { normalizeReferrerURL } = require('internal/modules/helpers');
@@ -130,45 +157,32 @@ function maybeCacheSourceMap(filename, content, cjsModuleInstance, isGeneratedSo
   }
 
   const data = dataFromUrl(filename, sourceMapURL);
-  const url = data ? null : sourceMapURL;
-  if (cjsModuleInstance) {
-    getCjsSourceMapCache().set(cjsModuleInstance, {
-      __proto__: null,
-      filename,
-      lineLengths: lineLengths(content),
-      data,
-      url,
-      sourceURL,
-    });
-  } else if (isGeneratedSource) {
-    const entry = {
-      __proto__: null,
-      lineLengths: lineLengths(content),
-      data,
-      url,
-      sourceURL,
-    };
+  const entry = {
+    __proto__: null,
+    lineLengths: lineLengths(content),
+    data,
+    // Save the source map url if it is not a data url.
+    sourceMapURL: data ? null : sourceMapURL,
+    sourceURL,
+  };
+
+  if (isGeneratedSource) {
     generatedSourceMapCache.set(filename, entry);
     if (sourceURL) {
       generatedSourceMapCache.set(sourceURL, entry);
     }
-  } else {
-    // If there is no cjsModuleInstance and is not generated source assume we are in a
-    // "modules/esm" context.
-    const entry = {
-      __proto__: null,
-      lineLengths: lineLengths(content),
-      data,
-      url,
-      sourceURL,
-    };
-    esmSourceMapCache.set(filename, entry);
-    if (sourceURL) {
-      esmSourceMapCache.set(sourceURL, entry);
-    }
+    return;
   }
+  // If it is not a generated source, we assume we are in a "cjs/esm"
+  // context.
+  const keys = sourceURL ? [filename, sourceURL] : [filename];
+  getModuleSourceMapCache().set(keys, entry, moduleInstance);
 }
 
+/**
+ * Caches the source map if it is present in the eval'd source.
+ * @param {string} content - the eval'd source code
+ */
 function maybeCacheGeneratedSourceMap(content) {
   const sourceMapsEnabled = getSourceMapsEnabled();
   if (!(process.env.NODE_V8_COVERAGE || sourceMapsEnabled)) return;
@@ -186,6 +200,14 @@ function maybeCacheGeneratedSourceMap(content) {
   }
 }
 
+/**
+ * Resolves source map payload data from the source url and source map url.
+ * If the source map url is a data url, the data is returned.
+ * Otherwise the source map url is resolved to a file path and the file is read.
+ * @param {string} sourceURL - url of the source file
+ * @param {string} sourceMappingURL - url of the source map
+ * @returns {object} deserialized source map JSON object
+ */
 function dataFromUrl(sourceURL, sourceMappingURL) {
   try {
     const url = new URL(sourceMappingURL);
@@ -227,7 +249,11 @@ function lineLengths(content) {
   return output;
 }
 
-
+/**
+ * Read source map from file.
+ * @param {string} mapURL - file url of the source map
+ * @returns {object} deserialized source map JSON object
+ */
 function sourceMapFromFile(mapURL) {
   try {
     const fs = require('fs');
@@ -281,56 +307,44 @@ function sourcesToAbsolute(baseURL, data) {
   return data;
 }
 
-// WARNING: The `sourceMapCacheToObject` and `appendCJSCache` run during
-// shutdown. In particular, they also run when Workers are terminated, making
-// it important that they do not call out to any user-provided code, including
-// built-in prototypes that might have been tampered with.
+// WARNING: The `sourceMapCacheToObject` runs during shutdown. In particular,
+// it also runs when Workers are terminated, making it important that it does
+// not call out to any user-provided code, including built-in prototypes that
+// might have been tampered with.
 
 // Get serialized representation of source-map cache, this is used
 // to persist a cache of source-maps to disk when NODE_V8_COVERAGE is enabled.
 function sourceMapCacheToObject() {
-  const obj = { __proto__: null };
-
-  for (const { 0: k, 1: v } of esmSourceMapCache) {
-    obj[k] = v;
-  }
-
-  appendCJSCache(obj);
-
-  if (ObjectKeys(obj).length === 0) {
+  const moduleSourceMapCache = getModuleSourceMapCache();
+  if (moduleSourceMapCache.size === 0) {
     return undefined;
   }
-  return obj;
-}
 
-function appendCJSCache(obj) {
-  for (const value of getCjsSourceMapCache()) {
-    obj[value.filename] = {
+  const obj = { __proto__: null };
+  for (const { 0: k, 1: v } of moduleSourceMapCache) {
+    obj[k] = {
       __proto__: null,
-      lineLengths: value.lineLengths,
-      data: value.data,
-      url: value.url,
+      lineLengths: v.lineLengths,
+      data: v.data,
+      url: v.sourceMapURL,
     };
   }
+  return obj;
 }
 
+/**
+ * Find a source map for a given actual source URL or path.
+ * @param {string} sourceURL - actual source URL or path
+ * @returns {import('internal/source_map/source_map').SourceMap | undefined} a source map or undefined if not found
+ */
 function findSourceMap(sourceURL) {
   if (RegExpPrototypeExec(kLeadingProtocol, sourceURL) === null) {
     sourceURL = pathToFileURL(sourceURL).href;
   }
   if (!SourceMap) {
     SourceMap = require('internal/source_map/source_map').SourceMap;
   }
-  let entry = esmSourceMapCache.get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
-  if (entry === undefined) {
-    for (const value of getCjsSourceMapCache()) {
-      const filename = value.filename;
-      const cachedSourceURL = value.sourceURL;
-      if (sourceURL === filename || sourceURL === cachedSourceURL) {
-        entry = value;
-      }
-    }
-  }
+  const entry = getModuleSourceMapCache().get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
   if (entry === undefined) {
     return undefined;
   }