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>

Author: bcoe

doc/api/cli.md

@@ -1199,8 +1199,9 @@ 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
 {
@@ -1226,7 +1227,13 @@ 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';
+
+constdebug=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.
+constErrorToString=Error.prototype.toString;// Capture original toString.
+constprepareStackTrace=(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)){
+constf=overrideStackTrace.get(error);
+overrideStackTrace.delete(error);
+returnf(error,trace);
+}
+
+const{ SourceMap }=require('internal/source_map/source_map');
+consterrorString=ErrorToString.call(error);
+
+if(trace.length===0){
+returnerrorString;
+}
+constpreparedTrace=trace.map((t,i)=>{
+letstr=i!==0 ? '\n at ' : '';
+str=`${str}${t}`;
+try{
+constsourceMap=findSourceMap(t.getFileName(),error);
+if(sourceMap&&sourceMap.data){
+constsm=newSourceMap(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}:${col+1}`;
+}
+}
+}catch(err){
+debug(err.stack);
+}
+returnstr;
+});
+return`${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.
 constesmSourceMapCache=newMap();
 const{ fileURLToPath,URL}=require('url');
-const{ overrideStackTrace }=require('internal/errors');
 
 letexperimentalSourceMaps;
 functionmaybeCacheSourceMap(filename,content,cjsModuleInstance){
@@ -38,18 +37,22 @@ function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
 
 constmatch=content.match(/\/[*/]#\s+sourceMappingURL=(?<sourceMappingURL>[^\s]+)/);
 if(match){
+constdata=dataFromUrl(basePath,match.groups.sourceMappingURL);
+consturl=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.
+functionlineLengths(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.
+returncontent.split(/\n|\u2028|\u2029/).map((line)=>{
+returnline.length;
+});
+}
+
 functionsourceMapFromFile(sourceMapFile){
 try{
 constcontent=fs.readFileSync(sourceMapFile,'utf8');
@@ -161,56 +176,14 @@ function appendCJSCache(obj) {
 constvalue=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.
-constErrorToString=Error.prototype.toString;// Capture original toString.
-constprepareStackTrace=(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)){
-constf=overrideStackTrace.get(error);
-overrideStackTrace.delete(error);
-returnf(error,trace);
-}
-
-const{ SourceMap }=require('internal/source_map/source_map');
-consterrorString=ErrorToString.call(error);
-
-if(trace.length===0){
-returnerrorString;
-}
-constpreparedTrace=trace.map((t,i)=>{
-letstr=i!==0 ? '\n at ' : '';
-str=`${str}${t}`;
-try{
-constsourceMap=findSourceMap(t.getFileName(),error);
-if(sourceMap&&sourceMap.data){
-constsm=newSourceMap(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}:${col+1}`;
-}
-}
-}catch(err){
-debug(err.stack);
-}
-returnstr;
-});
-return`${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.
 functionfindSourceMap(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.
+{
+constcoverageDirectory=nextdir();
+spawnSync(process.execPath,[
+require.resolve('../fixtures/source-map/inline-base64.js')
+],{env: { ...process.env,NODE_V8_COVERAGE: coverageDirectory}});
+constsourceMap=getSourceMapFromCache(
+'inline-base64.js',
+coverageDirectory
+);
+assert.strictEqual(sourceMap.url,null);
+}
+
+// Persists line lengths for in-memory representation of source file.
+{
+constcoverageDirectory=nextdir();
+spawnSync(process.execPath,[
+require.resolve('../fixtures/source-map/istanbul-throw.js')
+],{env: { ...process.env,NODE_V8_COVERAGE: coverageDirectory}});
+constsourceMap=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]);
+}
+}
+
 functiongetSourceMapFromCache(fixtureFile,coverageDirectory){
 constjsonFiles=fs.readdirSync(coverageDirectory);
 for(constjsonFileofjsonFiles){