1 files changed, 152 insertions, 0 deletions
diff --git a/lib/internal/source_map.js b/lib/internal/source_map.js
new file mode 100644
index 0000000000..4b198ff598
--- /dev/null
+++ b/lib/internal/source_map.js
@@ -0,0 +1,152 @@
+'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 {
+  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');
+
+function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
+  if (!process.env.NODE_V8_COVERAGE) 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, {
+        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;
+}
+
+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.
+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}`] = value;
+    }
+  });
+}
+
+module.exports = {
+  sourceMapCacheToObject,
+  maybeCacheSourceMap
+};