Preserve output on command timeout

When a command times out, the system now preserves and returns any output
that was collected before the timeout occurred. This improves the user
experience by not losing potentially valuable partial output.

Changes:
- Add partial_output to CommandTimeoutError
- Capture and return partial output in timeout scenarios
- Update documentation to reflect new behavior

Fixes SWE-agent#29

Co-Authored-By: Erkin Alp Güney <[email protected]>

Author: devin-ai-integration[bot]

Diff for: src/swerex/exceptions.py

@@ -25,7 +25,18 @@ def __init__(self, message: str, *, extra_info: dict[str, Any] = None):
         self.extra_info = extra_info
 
 
-class CommandTimeoutError(SwerexException, RuntimeError, TimeoutError): ...
+class CommandTimeoutError(SwerexException, RuntimeError, TimeoutError):
+    """Raised when a command times out, but includes any output collected before the timeout.
+
+    Attributes:
+        partial_output (str): The output that was collected before the timeout occurred
+    """
+    def __init__(self, message: str, partial_output: str = "", *, extra_info: dict[str, Any] = None):
+        super().__init__(message)
+        self.partial_output = partial_output
+        if extra_info is None:
+            extra_info = {}
+        self.extra_info = extra_info
 
 
 class NoExitCodeError(SwerexException, RuntimeError): ...

Diff for: src/swerex/runtime/local.py

@@ -217,12 +217,12 @@ async def run(self, action: BashAction | BashInterruptAction) -> BashObservation
 
         Raises:
             SessionNotInitializedError: If the shell is not initialized.
-            CommandTimeoutError: If the command times out.
+            CommandTimeoutError: If the command times out. The error will contain any output collected before the timeout.
             NonZeroExitCodeError: If the command has a non-zero exit code and `action.check` is True.
             NoExitCodeError: If we cannot get the exit code of the command.
 
         Returns:
-            BashObservation: The observation of the command.
+            BashObservation: The observation of the command, including any partial output if a timeout occurred.
         """
         if self.shell is None:
             msg = "shell not initialized"
@@ -231,7 +231,11 @@ async def run(self, action: BashAction | BashInterruptAction) -> BashObservation
             return await self.interrupt(action)
         if action.is_interactive_command or action.is_interactive_quit:
             return await self._run_interactive(action)
-        r = await self._run_normal(action)
+        try:
+            r = await self._run_normal(action)
+        except CommandTimeoutError as e:
+            # Return partial output on timeout
+            return BashObservation(output=e.partial_output, exit_code=None, failure_reason="timeout")
         if action.check == "raise" and r.exit_code != 0:
             msg = (
                 f"Command {action.command!r} failed with exit code {r.exit_code}. " f"Here is the output:\n{r.output!r}"
@@ -309,8 +313,9 @@ async def _run_normal(self, action: BashAction) -> BashObservation:
             expect_index = self.shell.expect(expect_strings, timeout=action.timeout)  # type: ignore
             matched_expect_string = expect_strings[expect_index]
         except pexpect.TIMEOUT as e:
+            partial_output = _strip_control_chars(self.shell.before).strip()  # type: ignore
             msg = f"timeout after {action.timeout} seconds while running command {action.command!r}"
-            raise CommandTimeoutError(msg) from e
+            raise CommandTimeoutError(msg, partial_output=partial_output) from e
         output: str = _strip_control_chars(self.shell.before).strip()  # type: ignore
 
         # Part 3: Get the exit code