lib: suppress source map lookup exceptions

benchmark/fixtures/simple-error-stack.ts

@@ -5,11 +5,13 @@
 const lorem = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.';
 
 function simpleErrorStack() {
-  try {
-    (lorem as any).BANG();
-  } catch (e) {
-    return e.stack;
-  }
+  [1].map(() => {
+    try {
+      (lorem as any).BANG();
+    } catch (e) {
+      return e.stack;
+    }
+  })
 }
 
 export {

lib/internal/source_map/prepare_stack_trace.js

@@ -53,9 +53,15 @@ function prepareStackTraceWithSourceMaps(error, trace) {
       const sm = fileName === lastFileName ?
         lastSourceMap :
         findSourceMap(fileName);
-      lastSourceMap = sm;
-      lastFileName = fileName;
+      // Only when a source map is found, cache it for the next iteration.
+      // This is a performance optimization to avoid interleaving with JS builtin function
+      // invalidating the cache.
+      // - at myFunc (file:///path/to/file.js:1:2)
+      // - at Array.map (<anonymous>)
+      // - at myFunc (file:///path/to/file.js:3:4)
       if (sm) {
+        lastSourceMap = sm;
+        lastFileName = fileName;
         return `${kStackLineAt}${serializeJSStackFrame(sm, callSite, trace[i + 1])}`;
       }
     } catch (err) {

lib/internal/source_map/source_map_cache.js

@@ -155,6 +155,9 @@ function maybeCacheSourceMap(filename, content, moduleInstance, isGeneratedSourc
   }
 
   const data = dataFromUrl(filename, sourceMapURL);
+  // `data` could be null if the source map is invalid.
+  // In this case, create a cache entry with null data with source url for test coverage.
+
   const entry = {
     __proto__: null,
     lineLengths: lineLengths(content),
@@ -277,6 +280,8 @@ function sourceMapFromDataUrl(sourceURL, url) {
       const parsedData = JSONParse(decodedData);
       return sourcesToAbsolute(sourceURL, parsedData);
     } catch (err) {
+      // TODO(legendecas): warn about invalid source map JSON string.
+      // But it could be verbose.
       debug(err);
       return null;
     }
@@ -331,24 +336,43 @@ function sourceMapCacheToObject() {
 
 /**
  * Find a source map for a given actual source URL or path.
+ *
+ * This function may be invoked from user code or test runner, this must not throw
+ * any exceptions.
  * @param {string} sourceURL - actual source URL or path
  * @returns {import('internal/source_map/source_map').SourceMap | undefined} a source map or undefined if not found
  */
 function findSourceMap(sourceURL) {
-  if (RegExpPrototypeExec(kLeadingProtocol, sourceURL) === null) {
-    sourceURL = pathToFileURL(sourceURL).href;
+  if (typeof sourceURL !== 'string') {
+    return undefined;
   }
-  SourceMap ??= require('internal/source_map/source_map').SourceMap;
-  const entry = getModuleSourceMapCache().get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
-  if (entry === undefined) {
+
+  // No source maps for builtin modules.
+  if (sourceURL.startsWith('node:')) {
     return undefined;
   }
-  let sourceMap = entry.sourceMap;
-  if (sourceMap === undefined) {
-    sourceMap = new SourceMap(entry.data, { lineLengths: entry.lineLengths });
-    entry.sourceMap = sourceMap;
+
+  SourceMap ??= require('internal/source_map/source_map').SourceMap;
+  try {
+    if (RegExpPrototypeExec(kLeadingProtocol, sourceURL) === null) {
+      // If the sourceURL is an invalid path, this will throw an error.
+      sourceURL = pathToFileURL(sourceURL).href;
+    }
+    const entry = getModuleSourceMapCache().get(sourceURL) ?? generatedSourceMapCache.get(sourceURL);
+    if (entry?.data == null) {
+      return undefined;
+    }
+
+    let sourceMap = entry.sourceMap;
+    if (sourceMap === undefined) {
+      sourceMap = new SourceMap(entry.data, { lineLengths: entry.lineLengths });
+      entry.sourceMap = sourceMap;
+    }
+    return sourceMap;
+  } catch (err) {
+    debug(err);
+    return undefined;
   }
-  return sourceMap;
 }
 
 module.exports = {