process: add source-map support to stack traces

PR-URL: https://github.com/nodejs/node/pull/29564
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 237 insertions, 0 deletions

diff --git a/lib/internal/source_map/source_map_cache.js b/lib/internal/source_map/source_map_cache.js
new file mode 100644
index 0000000000..94a4165546
--- /dev/null
+++ b/lib/internal/source_map/source_map_cache.js
@@ -0,0 +1,237 @@
+'use strict';
+
+// See https://sourcemaps.info/spec.html for SourceMap V3 specification.
+const { Buffer } = require('buffer');
+const debug = require('internal/util/debuglog').debuglog('source_map');
+const { dirname, resolve } = require('path');
+const fs = require('fs');
+const { getOptionValue } = require('internal/options');
+const {
+  normalizeReferrerURL,
+} = require('internal/modules/cjs/helpers');
+const { JSON, Object } = primordials;
+// For cjs, since Module._cache is exposed to users, we use a WeakMap
+// keyed on module, facilitating garbage collection.
+const cjsSourceMapCache = new WeakMap();
+// The esm cache is not exposed to users, so we can use a Map keyed
+// on filenames.
+const esmSourceMapCache = new Map();
+const { fileURLToPath, URL } = require('url');
+const { overrideStackTrace } = require('internal/errors');
+
+let experimentalSourceMaps;
+function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
+  if (experimentalSourceMaps === undefined) {
+    experimentalSourceMaps = getOptionValue('--enable-source-maps');
+  }
+  if (!(process.env.NODE_V8_COVERAGE || experimentalSourceMaps)) return;
+  let basePath;
+  try {
+    filename = normalizeReferrerURL(filename);
+    basePath = dirname(fileURLToPath(filename));
+  } catch (err) {
+    // This is most likely an [eval]-wrapper, which is currently not
+    // supported.
+    debug(err.stack);
+    return;
+  }
+
+  const match = content.match(/\/[*/]#\s+sourceMappingURL=(?<sourceMappingURL>[^\s]+)/);
+  if (match) {
+    if (cjsModuleInstance) {
+      cjsSourceMapCache.set(cjsModuleInstance, {
+        filename,
+        url: match.groups.sourceMappingURL,
+        data: dataFromUrl(basePath, match.groups.sourceMappingURL)
+      });
+    } else {
+      // If there is no cjsModuleInstance assume we are in a
+      // "modules/esm" context.
+      esmSourceMapCache.set(filename, {
+        url: match.groups.sourceMappingURL,
+        data: dataFromUrl(basePath, match.groups.sourceMappingURL)
+      });
+    }
+  }
+}
+
+function dataFromUrl(basePath, sourceMappingURL) {
+  try {
+    const url = new URL(sourceMappingURL);
+    switch (url.protocol) {
+      case 'data:':
+        return sourceMapFromDataUrl(basePath, url.pathname);
+      default:
+        debug(`unknown protocol ${url.protocol}`);
+        return null;
+    }
+  } catch (err) {
+    debug(err.stack);
+    // If no scheme is present, we assume we are dealing with a file path.
+    const sourceMapFile = resolve(basePath, sourceMappingURL);
+    return sourceMapFromFile(sourceMapFile);
+  }
+}
+
+function sourceMapFromFile(sourceMapFile) {
+  try {
+    const content = fs.readFileSync(sourceMapFile, 'utf8');
+    const data = JSON.parse(content);
+    return sourcesToAbsolute(dirname(sourceMapFile), data);
+  } catch (err) {
+    debug(err.stack);
+    return null;
+  }
+}
+
+// data:[<mediatype>][;base64],<data> see:
+// https://tools.ietf.org/html/rfc2397#section-2
+function sourceMapFromDataUrl(basePath, url) {
+  const [format, data] = url.split(',');
+  const splitFormat = format.split(';');
+  const contentType = splitFormat[0];
+  const base64 = splitFormat[splitFormat.length - 1] === 'base64';
+  if (contentType === 'application/json') {
+    const decodedData = base64 ?
+      Buffer.from(data, 'base64').toString('utf8') : data;
+    try {
+      const parsedData = JSON.parse(decodedData);
+      return sourcesToAbsolute(basePath, parsedData);
+    } catch (err) {
+      debug(err.stack);
+      return null;
+    }
+  } else {
+    debug(`unknown content-type ${contentType}`);
+    return null;
+  }
+}
+
+// If the sources are not absolute URLs after prepending of the "sourceRoot",
+// the sources are resolved relative to the SourceMap (like resolving script
+// src in a html document).
+function sourcesToAbsolute(base, data) {
+  data.sources = data.sources.map((source) => {
+    source = (data.sourceRoot || '') + source;
+    if (!/^[\\/]/.test(source[0])) {
+      source = resolve(base, source);
+    }
+    if (!source.startsWith('file://')) source = `file://${source}`;
+    return source;
+  });
+  // The sources array is now resolved to absolute URLs, sourceRoot should
+  // be updated to noop.
+  data.sourceRoot = '';
+  return data;
+}
+
+// Move source map from garbage collected module to alternate key.
+function rekeySourceMap(cjsModuleInstance, newInstance) {
+  const sourceMap = cjsSourceMapCache.get(cjsModuleInstance);
+  if (sourceMap) {
+    cjsSourceMapCache.set(newInstance, sourceMap);
+  }
+}
+
+// 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 = Object.create(null);
+
+  for (const [k, v] of esmSourceMapCache) {
+    obj[k] = v;
+  }
+  appendCJSCache(obj);
+
+  if (Object.keys(obj).length === 0) {
+    return undefined;
+  } else {
+    return obj;
+  }
+}
+
+// Since WeakMap can't be iterated over, we use Module._cache's
+// keys to facilitate Source Map serialization.
+//
+// TODO(bcoe): this means we don't currently serialize source-maps attached
+// to error instances, only module instances.
+function appendCJSCache(obj) {
+  const { Module } = require('internal/modules/cjs/loader');
+  Object.keys(Module._cache).forEach((key) => {
+    const value = cjsSourceMapCache.get(Module._cache[key]);
+    if (value) {
+      obj[`file://${key}`] = {
+        url: value.url,
+        data: value.data
+      };
+    }
+  });
+}
+
+// Create a prettified stacktrace, inserting context from source maps
+// if possible.
+const ErrorToString = Error.prototype.toString; // Capture original toString.
+const prepareStackTrace = (globalThis, error, trace) => {
+  // API for node internals to override error stack formatting
+  // without interfering with userland code.
+  // TODO(bcoe): add support for source-maps to repl.
+  if (overrideStackTrace.has(error)) {
+    const f = overrideStackTrace.get(error);
+    overrideStackTrace.delete(error);
+    return f(error, trace);
+  }
+
+  const { SourceMap } = require('internal/source_map/source_map');
+  const errorString = ErrorToString.call(error);
+
+  if (trace.length === 0) {
+    return errorString;
+  }
+  const preparedTrace = trace.map((t, i) => {
+    let str = i !== 0 ? '\n    at ' : '';
+    str = `${str}${t}`;
+    try {
+      const sourceMap = findSourceMap(t.getFileName(), error);
+      if (sourceMap && sourceMap.data) {
+        const sm = new SourceMap(sourceMap.data);
+        // Source Map V3 lines/columns use zero-based offsets whereas, in
+        // stack traces, they start at 1/1.
+        const [, , url, line, col] =
+                   sm.findEntry(t.getLineNumber() - 1, t.getColumnNumber() - 1);
+        if (url && line !== undefined && col !== undefined) {
+          str +=
+            `\n        -> ${url.replace('file://', '')}:${line + 1}:${col + 1}`;
+        }
+      }
+    } catch (err) {
+      debug(err.stack);
+    }
+    return str;
+  });
+  return `${errorString}\n    at ${preparedTrace.join('')}`;
+};
+
+// Attempt to lookup a source map, which is either attached to a file URI, or
+// keyed on an error instance.
+function findSourceMap(uri, error) {
+  const { Module } = require('internal/modules/cjs/loader');
+  let sourceMap = cjsSourceMapCache.get(Module._cache[uri]);
+  if (!uri.startsWith('file://')) uri = normalizeReferrerURL(uri);
+  if (sourceMap === undefined) {
+    sourceMap = esmSourceMapCache.get(uri);
+  }
+  if (sourceMap === undefined) {
+    const candidateSourceMap = cjsSourceMapCache.get(error);
+    if (candidateSourceMap && uri === candidateSourceMap.filename) {
+      sourceMap = candidateSourceMap;
+    }
+  }
+  return sourceMap;
+}
+
+module.exports = {
+  maybeCacheSourceMap,
+  prepareStackTrace,
+  rekeySourceMap,
+  sourceMapCacheToObject,
+};