fix: Improve source map stripping to reduce collisions

Author: rschristian

src/plugins/prerender-plugin.js

@@ -507,10 +507,12 @@ export function prerenderPlugin({ prerenderScript, renderTarget, additionalPrere
                         if (output.endsWith('.js')) {
                             const codeOrSource = bundle[output].type == 'chunk' ? 'code' : 'source';
                             if (typeof bundle[output][codeOrSource] !== 'string') continue;
-                            bundle[output][codeOrSource] = bundle[output][codeOrSource].replace(
-                                /\n\/\/#\ssourceMappingURL=.*/,
-                                '',
-                            );
+
+                            const linesOfCode = bundle[output][codeOrSource].trimEnd().split('\n');
+                            if (/^\/\/#\ssourceMappingURL=.*\.map$/.test(linesOfCode.at(-1))) {
+                                linesOfCode.pop();
+                                bundle[output][codeOrSource] = linesOfCode.join('\n');
+                            }
                         }
                     }
                 }

tests/fixtures/source-maps/src/index.js

@@ -11,3 +11,15 @@ if (typeof window !== 'undefined') {
 export async function prerender() {
     return `<h1>Simple Test Result</h1>`;
 }
+
+// Basically mirror preact-www's repl worker
+const PREPEND = `(function (module, exports) {\n`;
+const APPEND = `\n});`;
+export async function process() {
+    const code = `console.log('Hello World');`;
+    let transpiled = `${PREPEND}${code}${APPEND}`;
+
+    transpiled += '\n//# sourceMappingURL=' + 'some-url.js.map';
+
+    return transpiled;
+}

tests/source-maps.test.js

@@ -32,14 +32,17 @@ test('Should strip sourcemaps by default', async () => {
         outDirAssets.find((f) => /^index-.*\.js$/.test(f)),
     );
     const outputChunkCode = await fs.readFile(outputChunk, 'utf-8');
-    assert.is(outputChunkCode.match(/\/\/#\ssourceMappingURL=(.*)/), null);
+    // Ensure arbitrary strings don't get stripped
+    assert.ok(outputChunkCode.match(/\/\/#\ssourceMappingURL=/));
+    // Ensure the sourcemap comment has been removed
+    assert.is(outputChunkCode.match(/^\/\/#\ssourceMappingURL=.*\.map$/m), null);
 
     const outputAsset = path.join(
         outDir,
         outDirAssets.find((f) => /^worker-.*\.js$/.test(f)),
     );
     const outputAssetSource = await fs.readFile(outputAsset, 'utf-8');
-    assert.is(outputAssetSource.match(/\/\/#\ssourceMappingURL=(.*)/), null);
+    assert.is(outputAssetSource.match(/^\/\/#\ssourceMappingURL=.*\.map$/m), null);
 });
 
 test('Should preserve sourcemaps if user has enabled them', async () => {
@@ -64,7 +67,7 @@ test('Should preserve sourcemaps if user has enabled them', async () => {
     const outputJs = await fs.readFile(path.join(outDir, outputJsFileName), 'utf-8');
     assert.match(outputJs, '//# sourceMappingURL=');
 
-    const outputMap = outputJs.match(/\/\/#\ssourceMappingURL=(.*)/)[1];
+    const outputMap = outputJs.match(/^\/\/#\ssourceMappingURL=(.*)\.map$/m)[1];
     assert.ok(outDirAssets.includes(outputMap));
 });