Fix jj large-file warnings leaking into UI output

[ArthurHeymans]

Summary

Fix jj stderr warnings leaking into Majutsu UI output when jj refuses to snapshot large untracked files, such as binary/reference files above snapshot.max-new-file-size.

The leak showed up in two places:

• rendered buffers such as diff/status, because majutsu-jj-wash inserted jj output with stderr mixed into stdout;
• machine-readable/completion paths, because the responsive process-file replacement did not honor explicit nil stderr destinations like (list t nil), allowing warnings to be parsed as candidates.

Changes

• Route explicit nil stderr destinations to a throwaway stderr process in the responsive process runner, matching process-file semantics.
• Capture stderr separately in majutsu-jj-wash.
  • Successful commands now render stdout only.
  • Failing commands still include stderr when the caller requests error output.
• Add regression tests for discarded stderr, successful warning stderr, and preserved failure stderr.

Validation

• Ran the majutsu-process-test.el and majutsu-jj-test.el test files together: 66/66 passed.
• Manually verified against a jj worktree with large untracked pdf files: the snapshot warning no longer appears in washed status/diff output.

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of command errors so error output is preserved when requested and discarded when not needed.
  • Fixed temporary error-output cleanup to avoid leaving behind leftover files.
  • Prevented error text from being mixed into normal output when it should be suppressed.

• Tests

  • Added regression tests covering successful runs, failed runs with preserved error output, and cases where error output is explicitly disabled.

[coderabbitai]

Walkthrough

The process runner (majutsu--process-file-responsive) is updated to discard stderr without mixing it into stdout when the caller passes nil as the stderr destination. The jj wash layer (majutsu-jj-wash) gains a guaranteed err-file temp-file lifecycle via unwind-protect, conditional insertion of stderr content when keep-error is set, and explicit temp-file cleanup on return.

Changes

stderr discard and keep-error handling

Layer / File(s)	Summary
Process runner stderr discard fix majutsu-process.el, test/majutsu-process-test.el	Adds a stderr-discard flag; creates a temporary stderr buffer for both string-path and nil destinations, but restricts write-region flush to string-path destinations only. New regression test confirms stdout-only output when stderr destination is nil.
majutsu-jj-wash err-file lifecycle and keep-error insertion majutsu-jj.el, test/majutsu-jj-test.el	Wraps majutsu-process-file call in unwind-protect and writes an empty err-file when the command does not produce one. Inserts err-file contents into the buffer on the no-output and non-zero-exit branches when keep-error is non-nil. Cleans up err-file via prog1/ignore-errors on return. Two new ERT tests cover stderr discard on success and stderr preservation on failure.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 A rabbit digs tunnels for stderr to hide,
No errors shall leak to the stdout inside.
keep-error speaks up when the exit is bad,
And prog1 cleans temp files — no litter to add!
With unwind-protect guarding each burrow at night,
The wash basin gleams and the output is right. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: jj large-file warnings leaking into UI output.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

majutsu-jj.el (1)

872-884: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Colorize kept stderr before returning.

These new insert-file-contents paths run after the existing ANSI pass, so KEEP-ERROR now inserts raw stderr escape sequences into the buffer. Since Majutsu runs jj with --color=always by default, failing commands can render unreadable control bytes here.

Suggested fix

       (when keep-error
-        (insert-file-contents err-file))
+        (let ((err-beg (point)))
+          (insert-file-contents err-file)
+          (when (and majutsu-process-apply-ansi-colors
+                     (> (point) err-beg))
+            (let ((ansi-color-apply-face-function
+                   #'ansi-color-apply-text-property-face))
+              (ansi-color-apply-on-region err-beg (point))))))
@@
       (when keep-error
-        (insert-file-contents err-file))
+        (let ((err-beg (point)))
+          (insert-file-contents err-file)
+          (when (and majutsu-process-apply-ansi-colors
+                     (> (point) err-beg))
+            (let ((ansi-color-apply-face-function
+                   #'ansi-color-apply-text-property-face))
+              (ansi-color-apply-on-region err-beg (point))))))

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@majutsu-jj.el` around lines 872 - 884, Kept stderr is being inserted without
ANSI cleanup in the `keep-error` and failure-path branches of `majutsu-jj.el`,
so raw escape sequences can reach the buffer after the existing color-processing
step. Update the `insert-file-contents` handling in the `wash-jj-output` flow to
run the same ANSI stripping/colorization logic on `err-file` before inserting
it, especially in the `keep-error` path and the nonzero-exit failure branch. Use
the surrounding `keep-error`, `wash-anyway`, and `exit` handling in this
function to ensure all retained stderr is rendered consistently.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@majutsu-jj.el`:
- Around line 872-884: Kept stderr is being inserted without ANSI cleanup in the
`keep-error` and failure-path branches of `majutsu-jj.el`, so raw escape
sequences can reach the buffer after the existing color-processing step. Update
the `insert-file-contents` handling in the `wash-jj-output` flow to run the same
ANSI stripping/colorization logic on `err-file` before inserting it, especially
in the `keep-error` path and the nonzero-exit failure branch. Use the
surrounding `keep-error`, `wash-anyway`, and `exit` handling in this function to
ensure all retained stderr is rendered consistently.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 27e46d86-7cc3-4601-9245-49b542445e67

📥 Commits

Reviewing files that changed from the base of the PR and between 9c93891 and 616828f.

📒 Files selected for processing (4)

• majutsu-jj.el
• majutsu-process.el
• test/majutsu-jj-test.el
• test/majutsu-process-test.el