lib: suppress source map lookup exceptions

When the source map data are invalid json strings, skip construct
SourceMap on it. Additionally, suppress exceptions on source map lookups
and fix test runners crash on invalid source maps.

Author: legendecas

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 +336,38 @@ 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) {
+  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;
   }
-  let sourceMap = entry.sourceMap;
-  if (sourceMap === undefined) {
-    sourceMap = new SourceMap(entry.data, { lineLengths: entry.lineLengths });
-    entry.sourceMap = sourceMap;
-  }
-  return sourceMap;
 }
 
 module.exports = {