refactor: use XML-style tags for stdio discovery output

- Replace magic string prefixes with self-documenting XML tags
- Add explicit start/end markers to handle OS buffering edge cases
- Make regex parsing more robust and less greedy
- Addresses review comment about regex being too greedy

Author: taeold

scripts/bin-test/test.ts

@@ -210,7 +210,7 @@ async function runStdioDiscovery(modulePath: string): Promise<DiscoveryResult> {
 
     proc.on("close", () => {
       clearTimeout(timeoutId);
-      const manifestMatch = stderr.match(/__FIREBASE_FUNCTIONS_MANIFEST__:([\s\S]+)/);
+      const manifestMatch = stderr.match(/<FIREBASE_FUNCTIONS_MANIFEST>\n([\s\S]+?)\n<\/FIREBASE_FUNCTIONS_MANIFEST>/);
       if (manifestMatch) {
         const base64 = manifestMatch[1];
         const manifestJson = Buffer.from(base64, "base64").toString("utf8");
@@ -219,7 +219,7 @@ async function runStdioDiscovery(modulePath: string): Promise<DiscoveryResult> {
         return;
       }
 
-      const errorMatch = stderr.match(/__FIREBASE_FUNCTIONS_MANIFEST_ERROR__:([\s\S]+)/);
+      const errorMatch = stderr.match(/<FIREBASE_FUNCTIONS_MANIFEST_ERROR>\n([\s\S]+?)\n<\/FIREBASE_FUNCTIONS_MANIFEST_ERROR>/);
       if (errorMatch) {
         resolve({ success: false, error: errorMatch[1] });
         return;

src/bin/firebase-functions.ts

@@ -49,21 +49,23 @@ if (args.length > 1) {
   functionsDir = args[0];
 }
 
-const MANIFEST_PREFIX = "__FIREBASE_FUNCTIONS_MANIFEST__:";
-const MANIFEST_ERROR_PREFIX = "__FIREBASE_FUNCTIONS_MANIFEST_ERROR__:";
+const MANIFEST_START_TAG = "<FIREBASE_FUNCTIONS_MANIFEST>";
+const MANIFEST_END_TAG = "</FIREBASE_FUNCTIONS_MANIFEST>";
+const MANIFEST_ERROR_START_TAG = "<FIREBASE_FUNCTIONS_MANIFEST_ERROR>";
+const MANIFEST_ERROR_END_TAG = "</FIREBASE_FUNCTIONS_MANIFEST_ERROR>";
 
 async function runStdioDiscovery() {
   try {
     const stack = await loadStack(functionsDir);
     const wireFormat = stackToWire(stack);
     const manifestJson = JSON.stringify(wireFormat);
     const base64 = Buffer.from(manifestJson).toString("base64");
-    process.stderr.write(`${MANIFEST_PREFIX}${base64}\n`);
+    process.stderr.write(`${MANIFEST_START_TAG}\n${base64}\n${MANIFEST_END_TAG}\n`);
     process.exitCode = 0;
   } catch (e) {
     console.error("Failed to generate manifest from function source:", e);
     const message = e instanceof Error ? e.message : String(e);
-    process.stderr.write(`${MANIFEST_ERROR_PREFIX}${message}\n`);
+    process.stderr.write(`${MANIFEST_ERROR_START_TAG}\n${message}\n${MANIFEST_ERROR_END_TAG}\n`);
     process.exitCode = 1;
   }
 }