fix: decode subprocess output with errors="replace" to keep the reader thread alive

src/openjd/adaptor_runtime/process/_logging_subprocess.py

@@ -64,6 +64,13 @@ def __init__(
             stderr=subprocess.PIPE,
             stdout=subprocess.PIPE,
             encoding=encoding,
+            # Decode the subprocess output leniently. DCC batch processes may emit
+            # locale-encoded (non-UTF-8) bytes on stdout/stderr; with the default strict
+            # error handling a single undecodable byte raises UnicodeDecodeError in the
+            # stream-reader thread, killing it. Once the reader thread is gone the pipe is
+            # no longer drained, the subprocess blocks on a full stdout pipe, and the job
+            # deadlocks. Replacing undecodable bytes keeps the reader alive.
+            errors="replace",
             cwd=startup_directory,
         )
         if OSName.is_windows():  # pragma: is-posix

test/openjd/adaptor_runtime/integ/process/test_integration_logging_subprocess.py

@@ -151,6 +151,37 @@ def test_log_levels(self, log_level: int, caplog):
 
         assert any(r.message == message and r.levelno == _STDERR_LEVEL for r in records)
 
+    @pytest.mark.timeout(10)
+    def test_non_utf8_output_does_not_kill_reader(self, caplog):
+        """
+        A subprocess that writes a non-UTF-8 (locale-encoded) byte to stdout must not kill the
+        stream-reader thread. If the reader thread dies, lines emitted after the undecodable byte
+        are never logged and the stdout pipe stops being drained, which can deadlock the subprocess.
+        This is a regression test for that failure mode; the undecodable byte must be tolerated and
+        subsequent output must still be logged.
+        """
+        # GIVEN
+        caplog.set_level(_STDOUT_LEVEL)
+        # 0xc7 is "Ç" in cp1252 and is not a valid standalone UTF-8 byte.
+        script = (
+            "import sys; "
+            "sys.stdout.buffer.write(b'before\\n'); "
+            "sys.stdout.buffer.write(b'bad \\xc7 byte\\n'); "
+            "sys.stdout.buffer.write(b'after\\n'); "
+            "sys.stdout.buffer.flush()"
+        )
+
+        # WHEN
+        p = LoggingSubprocess(args=[sys.executable, "-c", script])
+        p.wait()
+        p._cleanup_io_threads()
+
+        # THEN
+        # "after" is only logged if the reader thread survived the undecodable byte.
+        assert "after" in caplog.text
+        # The undecodable byte is replaced rather than raising.
+        assert "�" in caplog.text
+
     def test_executable_not_found(self):
         """When calling LoggingSubprocess with a missing executable, FileNotFoundError will be raised"""
         args = ["missing_executable"]

test/openjd/adaptor_runtime/unit/process/test_logging_subprocess.py

@@ -69,6 +69,7 @@ def test_process_creation(self, mock_popen: mock.Mock, mock_stream_logger: mock.
         popen_params = dict(
             args=args,
             encoding="utf-8",
+            errors="replace",
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
@@ -482,6 +483,7 @@ def test_startup_directory_default(self, mock_popen_autospec: mock.Mock):
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
             encoding="utf-8",
+            errors="replace",
             cwd=None,
         )
         if OSName.is_windows():
@@ -504,6 +506,7 @@ def test_start_directory(self, mock_popen_autospec: mock.Mock):
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
             encoding="utf-8",
+            errors="replace",
             cwd="startup_dir",
         )
         if OSName.is_windows():