fix: report fork-PR resolution errors instead of a traceback

[vitali87]

Summary

• pr-split split '#999' (or user:branch) printed a Python stack trace when fetch_fork_pr / fetch_fork_branch raised: nothing in split caught GitOperationError and there is no top-level handler. The call is now wrapped and the prepared ErrorMsg printed with exit code 1.
• fetch_fork_pr reported a same-repo PR as "not found or is not from a fork". It now raises a distinct PR_NOT_FROM_FORK message telling the user to pass the head branch name instead; a deleted fork (head.repo null) still reports PR_NOT_FOUND.

Test plan

• New tests: CLI reports the error without a traceback; same-repo PR gets the specific message
• uv run ruff check / ruff format --check clean
• uv run pytest -q — 446 passed

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Configuration used: defaults

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📥 Commits

Reviewing files that changed from the base of the PR and between d6c8930 and 19a65fe.

📒 Files selected for processing (5)

• pr_split/cli.py
• pr_split/exceptions.py
• pr_split/git_ops/prs.py
• tests/test_cli_coverage.py
• tests/test_git_prs_coverage.py

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[greptile-apps]

Greptile Summary

This change improves fork-reference failures by showing clean CLI errors and by distinguishing same-repository pull requests from deleted or missing forks. Runtime coverage confirmed that ordinary fork-resolution errors now exit cleanly and that same-repository and deleted-fork responses receive the intended messages. A malformed GitHub pull-request response still escapes as an uncaught JSON decoding exception, leaving users without a useful error message.

Confidence Score: 4/5

Not ready to merge until malformed pull-request responses are converted into the same user-facing resolution error path.

The affected command path was exercised with an authored runtime harness, which reproduced the uncaught JSON decoding exception while also confirming the intended clean handling for normal resolution errors.

Files Needing Attention: pr_split/git_ops/prs.py needs to normalize malformed GitHub response data before it reaches the CLI handler; pr_split/cli.py catches only the project exception hierarchy.

T-Rex Logs

What T-Rex did

• T-Rex produced a focused fork-reference runtime harness and captured the base revision, PR fix: report fork-PR resolution errors instead of a traceback #56 head, and focused PR fix: report fork-PR resolution errors instead of a traceback #56 test output to validate the P1 finding.
• T-Rex issued a second finding-proof for another P1 finding to ensure reviewer coverage.
• T-Rex performed general-contract-validation-proof work, documenting a malformed JSON head capture, the CLI error handling fixes, and the fork-classification behavior for related PRs.

_{Ran code and verified through T-Rex}

Comments Outside Diff (2)

1. pr_split/git_ops/prs.py, line 99 (link)

   Malformed pull-request responses bypass CLI error handling

   fetch_fork_pr calls json.loads without converting malformed GitHub output into a GitOperationError. A response such as not-json therefore makes split #44 terminate with an uncaught JSONDecodeError and no user-facing error, because split only catches PRSplitError. Normalize decoding and malformed-payload failures to a project error so this path receives the same clean CLI handling as other pull-request resolution failures.

   Artifacts

   
   

   Focused fork-reference runtime harness source

   • Authored Python harness that mocks GitHub and Git boundaries while invoking the actual Typer CLI and fork resolver paths, providing the exact executable reproduction.

   Base revision fork-reference runtime output

   • Executed harness output from the PR base revision, showing the original uncaught resolver error and pre-change combined fork message.

   PR #56 head fork-reference runtime output

   • Executed harness output from PR fix: report fork-PR resolution errors instead of a traceback #56 HEAD, proving the clean resolver and fork classification changes while exposing the remaining uncaught malformed-JSON exception.

   Focused PR #56 test output

   • Executed the three committed focused tests for CLI resolver handling, same-repository classification, and deleted forks; all passed.

   

   _{Ran code and verified through T-Rex}

2. pr_split/git_ops/prs.py:99; propagation gap pr_split/cli.py:735-739

   Malformed GitHub pull-request payload bypasses fork-reference CLI error handling

   • Bug
     • split #44 with a malformed GitHub API response (not-json) exits with an uncaught JSONDecodeError and emits no user-facing error. The runtime harness confirms the exception is not a PRSplitError, so the new handler does not handle it. Typer's in-process test runner captured no traceback text, but the unhandled exception itself is proven.
   • Cause
     • fetch_fork_pr calls json.loads(raw) without translating json.JSONDecodeError into GitOperationError; split catches only PRSplitError.
   • Fix
     • Wrap JSON decoding and payload extraction in fetch_fork_pr and raise GitOperationError(ErrorMsg.PR_NOT_FOUND(number=pr_number)) (or another explicit API-response error) from JSONDecodeError, KeyError, and malformed structural values.

   _{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "fix: report fork-PR resolution errors in..." | Re-trigger Greptile}

[vitali87]

Addressed the Greptile finding: fetch_fork_pr now converts a malformed API response (invalid JSON, non-object, missing head/base) into GitOperationError(PR_RESPONSE_INVALID), so it reaches the same clean CLI error path. Parametrised test added.

[greptile-apps]

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