[macros] ensure we close the socket if the process fails to start

Change-Id: I29a9583080d27ce286d0c2f9f7dfa2d267b60b9d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/332600
Commit-Queue: Konstantin Shcheglov <[email protected]>
Commit-Queue: Jake Macdonald <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Auto-Submit: Jake Macdonald <[email protected]>

Author: jakemac53

pkg/_fe_analyzer_shared/lib/src/macros/executor/process_executor.dart

@@ -60,11 +60,17 @@ class _SingleProcessMacroExecutor extends ExternalMacroExecutorBase {
     } on SocketException catch (_) {
       serverSocket = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
     }
-    Process process = await Process.start(programPath, [
-      ...arguments,
-      serverSocket.address.address,
-      serverSocket.port.toString(),
-    ]);
+    Process process;
+    try {
+      process = await Process.start(programPath, [
+        ...arguments,
+        serverSocket.address.address,
+        serverSocket.port.toString(),
+      ]);
+    } catch (e) {
+      await serverSocket.close();
+      rethrow;
+    }
     process.stderr
         .transform(const Utf8Decoder())
         .listen((content) => throw new RemoteException(content));