fix(cli): make lint-translations exit non-zero when translations differ

[Zuhef]

Problem

chainlit lint-translations reports differences and then exits 0, so it cannot gate anything. Issue #2993 identified this as the reason locale keys drift unnoticed, and it is true even for the app translations the command is actually pointed at.

The chain is silent end to end:

• lint_translation_json prints the differences and returns None
• lint_translations returns None
• chainlit_lint_translations calls it and ignores the result, so Click exits 0

Change

• lint_translation_json returns the differences it printed. Additive - existing callers that ignore the return value are unaffected, and the printed output is unchanged.
• lint_translations returns the total count across all linted files.
• The CLI command prints a summary and raises SystemExit(1) when the count is non-zero.

Two incidental cleanups in the same function: the per-file loop was nested inside the ground-truth with open(...) block, holding that handle open for the entire run, so it is dedented; and os.listdir is now sorted so the report order is deterministic. Happy to drop either if you would rather keep the diff to the exit code alone.

Verification

Ran on Windows against a directory containing all 23 packaged locales, comparing a clean main worktree with the patched tree:

	files linted	differences reported	exit code
main	23	6	0
patched	23	6	1

Same six differences either way - only the exit code changes. A directory whose translations match the ground truth still exits 0.

The six it finds are the real gaps from #2993, which is a useful independent cross-check: this is the CLI path rather than the test suite, and it reports exactly chat.favorites.remove (ar-SA, da-DK), components.DatePickerInput (de-DE, it, ko) and chat.fileUpload.browse (ja).

pytest backend/tests/test_translations.py - 39 passed. New tests cover the returned error list, the aggregate count for both clean and broken input, and that non-JSON files in the directory are ignored.

ruff format --check clean on all four files. ruff check reports two RUF036 findings at config.py:391-392, which are pre-existing and outside this change.

Note

While verifying this I hit a separate pre-existing problem: on a stock Windows console the command dies with a UnicodeEncodeError printing the ✅/❌ markers, since the console code page cannot encode them. It only runs with PYTHONIOENCODING=utf-8 set. That is independent of this change and I have not touched it here - happy to open a separate issue or PR for it if useful.

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Summary by cubic

Make chainlit lint-translations fail fast when translations differ. Previously it printed differences and exited 0; now it exits 1 so CI can gate locale changes.

• lint_translation_json returns the list of differences (printed output unchanged).
• lint_translations returns the total difference count and sorts the directory listing for deterministic reports.
• The CLI prints a summary and exits 1 when the count is non-zero.
• Moved the per-file loop out of the ground-truth with open(...) block to avoid holding the handle open.
• Tests cover returned errors, aggregate counts for clean/broken inputs, and ignoring non-JSON files.

^{Written for commit af2f7ad. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}

[dokterbob]

@codex review

[Copilot]

Pull request overview

Updates the translation linter so translation differences can reliably fail CI.

Changes:

• Returns detected differences and aggregates their count.
• Produces deterministic file ordering.
• Exits with status 1 and prints a summary when differences exist.
• Adds coverage for return values, counting, and file filtering.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
backend/chainlit/translations.py	Returns detected structural differences.
backend/chainlit/config.py	Aggregates differences across sorted translation files.
backend/chainlit/cli/__init__.py	Exits non-zero when differences are found.
backend/tests/test_translations.py	Tests difference reporting and aggregation.

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[dokterbob]

LGTM.