lib: don't parse windows drive letters as schemes

lib/internal/source_map/source_map_cache.js

@@ -39,6 +39,7 @@ const kLeadingProtocol = /^\w+:\/\//;
 const kSourceMappingURLMagicComment = /\/[*/]#\s+sourceMappingURL=(?<sourceMappingURL>[^\s]+)/g;
 const kSourceURLMagicComment = /\/[*/]#\s+sourceURL=(?<sourceURL>[^\s]+)/g;
 
+const { isAbsolute } = require('path');
 const { fileURLToPath, pathToFileURL, URL } = require('internal/url');
 
 let SourceMap;
@@ -251,9 +252,13 @@ function sourceMapFromDataUrl(sourceURL, 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).
+// If the sources are absolute paths, the sources are converted to absolute file URLs.
 function sourcesToAbsolute(baseURL, data) {
   data.sources = data.sources.map((source) => {
     source = (data.sourceRoot || '') + source;
+    if (isAbsolute(source)) {
+      return pathToFileURL(source).href;
+    }
     return new URL(source, baseURL).href;
   });
   // The sources array is now resolved to absolute URLs, sourceRoot should

test/fixtures/source-map/ts-node.ts

@@ -0,0 +1,11 @@
+function foo(str: string) {
+  return str;
+}
+
+foo('noop');
+
+// To recreate (Windows only):
+//
+// const filePath = require.resolve('./test/fixtures/source-map/ts-node.ts');
+// const compiled = require('ts-node').create({ transpileOnly: true }).compile(fs.readFileSync(filePath, 'utf8'), filePath);
+// fs.writeFileSync('test/fixtures/source-map/ts-node-win32.js', compiled);

test/parallel/test-source-map-enable.js

@@ -289,6 +289,30 @@ function nextdir() {
   assert.match(output.stderr.toString(), /at functionC.*10:3/);
 }
 
+// Properly converts Windows absolute paths to absolute URLs.
+// Refs: https://github.com/nodejs/node/issues/50523
+// Refs: https://github.com/TypeStrong/ts-node/issues/1769
+{
+  const coverageDirectory = nextdir();
+  const output = spawnSync(process.execPath, [
+    require.resolve('../fixtures/source-map/ts-node-win32.js'),
+  ], { env: { ...process.env, NODE_V8_COVERAGE: coverageDirectory } });
+  assert.strictEqual(output.status, 0);
+  assert.strictEqual(output.stderr.toString(), '');
+  const sourceMap = getSourceMapFromCache(
+    'ts-node-win32.js',
+    coverageDirectory
+  );
+  // base64 JSON should have been decoded, the D: in the sources field should
+  // have been taken as the drive letter on Windows, the scheme on POSIX.
+  assert.strictEqual(
+    sourceMap.data.sources[0],
+    common.isWindows ?
+      'file:///D:/workspaces/node/test/fixtures/source-map/ts-node.ts' :
+      'd:/workspaces/node/test/fixtures/source-map/ts-node.ts'
+  );
+}
+
 // Stores and applies source map associated with file that throws while
 // being required.
 {