process: add lineLength to source-map-cache

Without the line lengths of in-memory transpiled source, it's not
possible to convert from byte ofsets to line/column offsets.

PR-URL: #29863
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/cli.md

@@ -1191,8 +1191,9 @@ If found, Source Map data is appended to the top-level key `source-map-cache`
 on the JSON coverage object.
 
 `source-map-cache` is an object with keys representing the files source maps
-were extracted from, and the values include the raw source-map URL
-(in the key `url`) and the parsed Source Map V3 information (in the key `data`).
+were extracted from, and values which include the raw source-map URL
+(in the key `url`), the parsed Source Map V3 information (in the key `data`),
+and the line lengths of the source file (in the key `lineLengths`).
 
 ```json
 {
@@ -1218,7 +1219,13 @@ were extracted from, and the values include the raw source-map URL
  ],
  "mappings": "MAAMA,IACJC,YAAaC",
  "sourceRoot": "./"
- }
+ },
+ "lineLengths": [
+ 13,
+ 62,
+ 38,
+ 27
+ ]
  }
  }
 }

lib/internal/bootstrap/pre_execution.js

@@ -25,7 +25,7 @@ function prepareMainThreadExecution(expandArgv1 = false) {
  // prepareStackTrace method, replacing the default in errors.js.
  if (getOptionValue('--enable-source-maps')) {
  const { prepareStackTrace } =
- require('internal/source_map/source_map_cache');
+ require('internal/source_map/prepare_stack_trace');
  const { setPrepareStackTraceCallback } = internalBinding('errors');
  setPrepareStackTraceCallback(prepareStackTrace);
  }

lib/internal/source_map/prepare_stack_trace.js

@@ -0,0 +1,52 @@
+'use strict';
+
+const debug = require('internal/util/debuglog').debuglog('source_map');
+const { findSourceMap } = require('internal/source_map/source_map_cache');
+const { overrideStackTrace } = require('internal/errors');
+
+// 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('')}`;
+};
+
+module.exports = {
+ prepareStackTrace,
+};

lib/internal/source_map/source_map_cache.js

@@ -17,7 +17,6 @@ const cjsSourceMapCache = new WeakMap();
 // on filenames.
 const esmSourceMapCache = new Map();
 const { fileURLToPath, URL } = require('url');
-const { overrideStackTrace } = require('internal/errors');
 
 let experimentalSourceMaps;
 function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
@@ -38,18 +37,22 @@ function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
 
  const match = content.match(/\/[*/]#\s+sourceMappingURL=(?<sourceMappingURL>[^\s]+)/);
  if (match) {
+ const data = dataFromUrl(basePath, match.groups.sourceMappingURL);
+ const url = data ? null : match.groups.sourceMappingURL;
  if (cjsModuleInstance) {
  cjsSourceMapCache.set(cjsModuleInstance, {
  filename,
- url: match.groups.sourceMappingURL,
- data: dataFromUrl(basePath, match.groups.sourceMappingURL)
+ lineLengths: lineLengths(content),
+ data,
+ url
  });
  } 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)
+ lineLengths: lineLengths(content),
+ data,
+ url
  });
  }
  }
@@ -73,6 +76,18 @@ function dataFromUrl(basePath, sourceMappingURL) {
  }
 }
 
+// Cache the length of each line in the file that a source map was extracted
+// from. This allows translation from byte offset V8 coverage reports,
+// to line/column offset Source Map V3.
+function lineLengths(content) {
+ // We purposefully keep \r as part of the line-length calculation, in
+ // cases where there is a \r\n separator, so that this can be taken into
+ // account in coverage calculations.
+ return content.split(/\n|\u2028|\u2029/).map((line) => {
+ return line.length;
+ });
+}
+
 function sourceMapFromFile(sourceMapFile) {
  try {
  const content = fs.readFileSync(sourceMapFile, 'utf8');
@@ -161,56 +176,14 @@ function appendCJSCache(obj) {
  const value = cjsSourceMapCache.get(Module._cache[key]);
  if (value) {
  obj[`file://${key}`] = {
- url: value.url,
- data: value.data
+ lineLengths: value.lineLengths,
+ data: value.data,
+ url: value.url
  };
  }
  });
 }
 
-// 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) {
@@ -230,8 +203,8 @@ function findSourceMap(uri, error) {
 }
 
 module.exports = {
+ findSourceMap,
  maybeCacheSourceMap,
- prepareStackTrace,
  rekeySourceMap,
  sourceMapCacheToObject,
 };

node.gyp

@@ -176,6 +176,7 @@
  'lib/internal/repl/history.js',
  'lib/internal/repl/utils.js',
  'lib/internal/socket_list.js',
+ 'lib/internal/source_map/prepare_stack_trace.js',
  'lib/internal/source_map/source_map.js',
  'lib/internal/source_map/source_map_cache.js',
  'lib/internal/test/binding.js',

test/parallel/test-source-map.js

@@ -193,6 +193,36 @@ function nextdir() {
  );
 }
 
+// Does not persist url parameter if source-map has been parsed.
+{
+ const coverageDirectory = nextdir();
+ spawnSync(process.execPath, [
+ require.resolve('../fixtures/source-map/inline-base64.js')
+ ], { env: { ...process.env, NODE_V8_COVERAGE: coverageDirectory } });
+ const sourceMap = getSourceMapFromCache(
+ 'inline-base64.js',
+ coverageDirectory
+ );
+ assert.strictEqual(sourceMap.url, null);
+}
+
+// Persists line lengths for in-memory representation of source file.
+{
+ const coverageDirectory = nextdir();
+ spawnSync(process.execPath, [
+ require.resolve('../fixtures/source-map/istanbul-throw.js')
+ ], { env: { ...process.env, NODE_V8_COVERAGE: coverageDirectory } });
+ const sourceMap = getSourceMapFromCache(
+ 'istanbul-throw.js',
+ coverageDirectory
+ );
+ if (common.isWindows) {
+ assert.deepStrictEqual(sourceMap.lineLengths, [1086, 31, 185, 649, 0]);
+ } else {
+ assert.deepStrictEqual(sourceMap.lineLengths, [1085, 30, 184, 648, 0]);
+ }
+}
+
 function getSourceMapFromCache(fixtureFile, coverageDirectory) {
  const jsonFiles = fs.readdirSync(coverageDirectory);
  for (const jsonFile of jsonFiles) {