Fix and re-enable the commissioner-generated-passcode Linux tv CI test

Author: shaoltan-amazon

.github/workflows/examples-linux-tv-casting-app.yaml

@@ -72,16 +72,13 @@ jobs:
                     "python3 ./scripts/tests/run_tv_casting_test.py"
               timeout-minutes: 2 # Comment this out to debug if GitHub Action times out.
 
-            # TODO: this test is flaky and was disabled
-            #       https://github.com/project-chip/connectedhomeip/issues/34598
-            #
-            #  - name:
-            #        Test casting from Linux tv-casting-app to Linux tv-app -
-            #        Commissioner Generated Passcode
-            #    run: |
-            #        ./scripts/run_in_build_env.sh \
-            #          "python3 ./scripts/tests/run_tv_casting_test.py --commissioner-generated-passcode=True"
-            #    timeout-minutes: 2 # Comment this out to debug if GitHub Action times out.
+            - name:
+                  Test casting from Linux tv-casting-app to Linux tv-app -
+                  Commissioner Generated Passcode
+              run: |
+                  ./scripts/run_in_build_env.sh \
+                    "python3 ./scripts/tests/run_tv_casting_test.py --commissioner-generated-passcode=True"
+              timeout-minutes: 2 # Comment this out to debug if GitHub Action times out.
 
             - name: Uploading Size Reports
               uses: ./.github/actions/upload-size-reports

scripts/tests/linux/log_line_processing.py

@@ -63,26 +63,27 @@ def _io_thread(self):
         err_wait = select.poll()
         err_wait.register(self.process.stderr, select.POLLIN | select.POLLHUP)
 
-        with open(self.output_path, "wt") as f:
+        with open(self.output_path, "wt", buffering=1) as f:
             f.write("PROCESS START: %s\n" % time.ctime())
+            f.flush()
             while not self.done:
                 changes = out_wait.poll(0.1)
-                if changes:
-                    out_line = self.process.stdout.readline()
-                    if not out_line:
-                        # stdout closed (otherwise readline should have at least \n)
-                        continue
-                    f.write(out_line)
-                    self.output_lines.put(out_line)
-
-                changes = err_wait.poll(0)
-                if changes:
-                    err_line = self.process.stderr.readline()
-                    if not err_line:
-                        # stderr closed (otherwise readline should have at least \n)
-                        continue
-                    f.write(f"!!STDERR!! : {err_line}")
+                for fd, _ in changes:
+                    if fd == self.process.stdout.fileno():
+                        while True:
+                            out_line = self.process.stdout.readline()
+                            if not out_line:
+                                break
+                            f.write(out_line)
+                            f.flush()
+                            self.output_lines.put(out_line)
+                    elif fd == self.process.stderr.fileno():
+                        err_line = self.process.stderr.readline()
+                        if err_line:
+                            f.write(f"!!STDERR!! : {err_line}")
+                            f.flush()
             f.write("PROCESS END: %s\n" % time.ctime())
+            f.flush()
 
     def __enter__(self):
         self.done = False
@@ -92,6 +93,7 @@ def __enter__(self):
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
             text=True,
+            bufsize=1,
         )
         self.io_thread = threading.Thread(target=self._io_thread)
         self.io_thread.start()