fix: Make sourceMappingURL heuristic more resilient (#378)

Author: Luca Forstner

packages/bundler-plugin-core/src/debug-id-upload.ts

@@ -298,10 +298,35 @@ async function determineSourceMapPathFromBundle(
   const sourceMappingUrlMatch = bundleSource.match(/^\s*\/\/# sourceMappingURL=(.*)$/m);
   if (sourceMappingUrlMatch) {
     const sourceMappingUrl = path.normalize(sourceMappingUrlMatch[1] as string);
-    if (path.isAbsolute(sourceMappingUrl)) {
-      return sourceMappingUrl;
+
+    let isUrl;
+    let isSupportedUrl;
+    try {
+      const url = new URL(sourceMappingUrl);
+      isUrl = true;
+      isSupportedUrl = url.protocol === "file:";
+    } catch {
+      isUrl = false;
+      isSupportedUrl = false;
+    }
+
+    let absoluteSourceMapPath;
+    if (isSupportedUrl) {
+      absoluteSourceMapPath = sourceMappingUrl;
+    } else if (isUrl) {
+      return;
+    } else if (path.isAbsolute(sourceMappingUrl)) {
+      absoluteSourceMapPath = sourceMappingUrl;
     } else {
-      return path.join(path.dirname(bundlePath), sourceMappingUrl);
+      absoluteSourceMapPath = path.join(path.dirname(bundlePath), sourceMappingUrl);
+    }
+
+    try {
+      // Check if the file actually exists
+      await util.promisify(fs.access)(absoluteSourceMapPath);
+      return absoluteSourceMapPath;
+    } catch (e) {
+      // noop
     }
   }