errors: do not call resolve on URLs with schemes

Based on advice from webpack project, this PR stops trying to resolve
sources with a webpack:// scheme (or other schemes, as they represent
absolute URLs). Source content is now loaded from the sourcesContent
lookup, if it is populated (allowing for non file:// schemes).

Refs: #35325

Author: bcoe

lib/internal/source_map/prepare_stack_trace.js

@@ -40,14 +40,12 @@ const prepareStackTrace = (globalThis, error, trace) => {
   }
 
   let errorSource = '';
-  let firstSource;
   let firstLine;
   let firstColumn;
   const preparedTrace = trace.map((t, i) => {
     if (i === 0) {
       firstLine = t.getLineNumber();
       firstColumn = t.getColumnNumber();
-      firstSource = t.getFileName();
     }
     let str = i !== 0 ? '\n    at ' : '';
     str = `${str}${t}`;
@@ -63,16 +61,21 @@ const prepareStackTrace = (globalThis, error, trace) => {
         } = sm.findEntry(t.getLineNumber() - 1, t.getColumnNumber() - 1);
         if (originalSource && originalLine !== undefined &&
             originalColumn !== undefined) {
-          const originalSourceNoScheme = originalSource
-            .replace(/^file:\/\//, '');
           if (i === 0) {
             firstLine = originalLine + 1;
             firstColumn = originalColumn + 1;
-            firstSource = originalSourceNoScheme;
+
             // Show error in original source context to help user pinpoint it:
-            errorSource = getErrorSource(firstSource, firstLine, firstColumn);
+            errorSource = getErrorSource(
+              sm.payload,
+              originalSource,
+              firstLine,
+              firstColumn
+            );
           }
           // Show both original and transpiled stack trace information:
+          const originalSourceNoScheme = originalSource
+            .replace(/^file:\/\//, '');
           str += `\n        -> ${originalSourceNoScheme}:${originalLine + 1}:` +
             `${originalColumn + 1}`;
         }
@@ -88,15 +91,26 @@ const prepareStackTrace = (globalThis, error, trace) => {
 // 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.
-function getErrorSource(firstSource, firstLine, firstColumn) {
+function getErrorSource(payload, originalSource, firstLine, firstColumn) {
   let exceptionLine = '';
+  const originalSourceNoScheme = originalSource.replace(/^file:\/\//, '');
+
   let source;
-  try {
-    source = readFileSync(firstSource, 'utf8');
-  } catch (err) {
-    debug(err);
-    return exceptionLine;
+  const sourceContentIndex = payload.sources.indexOf(originalSource);
+  if (payload.sourcesContent?.[sourceContentIndex]) {
+    // First we check if the original source content was provided in the
+    // source map itself:
+    source = payload.sourcesContent[sourceContentIndex];
+  } else {
+    // If no sourcesContent was found, attempt to load the original source
+    // from disk:
+    try {
+      source = readFileSync(originalSourceNoScheme, 'utf8');
+    } catch (err) {
+      debug(err);
+    }
   }
+
   const lines = source.split(/\r?\n/, firstLine);
   const line = lines[firstLine - 1];
   if (!line) return exceptionLine;
@@ -110,7 +124,8 @@ function getErrorSource(firstSource, firstLine, firstColumn) {
   }
   prefix = prefix.slice(0, -1); // The last character is the '^'.
 
-  exceptionLine = `${firstSource}:${firstLine}\n${line}\n${prefix}^\n\n`;
+  exceptionLine =
+              `${originalSourceNoScheme}:${firstLine}\n${line}\n${prefix}^\n\n`;
   return exceptionLine;
 }
 

lib/internal/source_map/source_map_cache.js

@@ -165,14 +165,16 @@ function sourceMapFromDataUrl(basePath, url) {
 // 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).
+// TODO(bcoe): refactor to use new URL(url, base), rather than path.resolve.
 function sourcesToAbsolute(base, data) {
   data.sources = data.sources.map((source) => {
     source = (data.sourceRoot || '') + source;
+    // An absolute URI does not need to be resolved, return it:
+    if (source.match(/(?<scheme>^\w+):\/\//)) return source;
     if (!/^[\\/]/.test(source[0])) {
       source = resolve(base, source);
     }
-    if (!source.startsWith('file://')) source = `file://${source}`;
-    return source;
+    return `file://${source}`;
   });
   // The sources array is now resolved to absolute URLs, sourceRoot should
   // be updated to noop.

test/fixtures/source-map/webpack.js

@@ -265,6 +265,23 @@ function nextdir() {
   );
 }
 
+// Does not attempt to apply path resolution logic to absolute URLs
+// with schemes.
+// Refs: https://github.com/webpack/webpack/issues/9601
+// Refs: https://sourcemaps.info/spec.html#h.75yo6yoyk7x5
+{
+  const output = spawnSync(process.execPath, [
+    '--enable-source-maps',
+    require.resolve('../fixtures/source-map/webpack.js')
+  ]);
+  // Error in original context of source content:
+  assert.ok(
+    output.stderr.toString().match(/throw new Error\('oh no!'\)\n.*\^/)
+  );
+  // Rewritten stack trace:
+  assert.ok(output.stderr.toString().includes('webpack:///./webpack.js:14:9'));
+}
+
 function getSourceMapFromCache(fixtureFile, coverageDirectory) {
   const jsonFiles = fs.readdirSync(coverageDirectory);
   for (const jsonFile of jsonFiles) {