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lib: allow CJS source map cache to be reclaimed
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Unifies the CJS and ESM source map cache map with SourceMapCacheMap
and allows the CJS cache entries to be queried more efficiently with
a source url without iteration on an IterableWeakMap.

Add a test to verify that the CJS source map cache entry can be
reclaimed.

PR-URL: #51711
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
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@legendecas @targos
legendecas authored and targos committed Jun 1, 2024
1 parent 374743c commit fe007cd
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Showing 16 changed files with 393 additions and 277 deletions.
4 changes: 2 additions & 2 deletions lib/internal/modules/cjs/loader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand All @@ -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;
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7 changes: 3 additions & 4 deletions lib/internal/modules/esm/translators.js
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Original file line number Diff line number Diff line change
Expand Up @@ -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
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2 changes: 1 addition & 1 deletion lib/internal/modules/esm/utils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
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25 changes: 22 additions & 3 deletions lib/internal/source_map/prepare_stack_trace.js
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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.
Expand All @@ -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) {
Expand Down
164 changes: 89 additions & 75 deletions lib/internal/source_map/source_map_cache.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@
const {
ArrayPrototypePush,
JSONParse,
ObjectKeys,
RegExpPrototypeExec,
SafeMap,
StringPrototypeCodePointAt,
Expand All @@ -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;
Expand All @@ -52,6 +49,10 @@ function getSourceMapsEnabled() {
return sourceMapsEnabled;
}

/**
* Enables or disables source maps programmatically.
* @param {boolean} val
*/
function setSourceMapsEnabled(val) {
validateBoolean(val, 'val');

Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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');
Expand All @@ -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;
Expand All @@ -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);
Expand Down Expand Up @@ -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');
Expand Down Expand Up @@ -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;
}
Expand Down
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