test(langfuse): structural guard for setup_hook + hook file coexistence

[yasinBursali]

DRAFT: must merge AFTER #1040. This PR's tests assert that langfuse's service.setup_hook and hooks/post_install.sh exist. Both are added by upstream PR #1040 (the langfuse postgres uid 70 install fix). Until #1040 merges, these tests fail on bare upstream/main — that's expected. Promote to ready-for-review after git rebase upstream/main post-#1040.

What

Add TestLangfuseManifestHook to dream-server/extensions/services/dashboard-api/tests/test_hooks.py. Two narrow structural-guard assertions that langfuse's manifest declares service.setup_hook = "hooks/post_install.sh" AND that the referenced hook file exists on disk.

Why

The langfuse postgres uid 70 install fix relies on service.setup_hook pointing at hooks/post_install.sh. If either drifts (file renamed, manifest field removed, hook deleted), the host agent's _validate_hook_path returns None, _handle_install silently skips the hook at the if hook_path: guard, and langfuse silently regresses to the broken Linux postgres uid mismatch behaviour with no CI signal. The structural guard catches that.

How

Append a single test class to the existing test_hooks.py (the established home for hook-related tests, sharing its import yaml, pathlib.Path, and class-based conventions):

class TestLangfuseManifestHook:
    def test_langfuse_manifest_declares_post_install_hook(self):
        ext_dir = Path(__file__).resolve().parents[2] / "langfuse"
        manifest = yaml.safe_load((ext_dir / "manifest.yaml").read_text())
        setup_hook = manifest.get("service", {}).get("setup_hook")
        assert setup_hook == "hooks/post_install.sh", (...)

    def test_langfuse_post_install_hook_file_exists(self):
        ext_dir = Path(__file__).resolve().parents[2] / "langfuse"
        hook_path = ext_dir / "hooks" / "post_install.sh"
        assert hook_path.is_file(), (...)

Path expression Path(__file__).resolve().parents[2] / "langfuse" is the corrected form: parents[0] = tests/, parents[1] = dashboard-api/, parents[2] = extensions/services/. (The original issue suggestion Path(__file__).resolve().parent.parent / "dream-server" / ... resolves to a nonexistent path — fixed during implementation.)

Defensive manifest.get("service", {}).get("setup_hook") mirrors the host agent's own style at line 441 — produces a clean AssertionError if the entire service: block is removed in some future regression, instead of a less-actionable KeyError.

Assertion messages reference the langfuse postgres uid 70 install fix conceptually rather than a transient PR number, so the wording remains accurate after rebase regardless of whether that fix's PR number changes.

Testing

• python3 -m py_compile → PASS
• ruff → clean (no new warnings, no unused imports)
• Path math validation: Path(__file__).resolve().parents[2] / "langfuse" resolves to extensions/services/langfuse ✓
• Bare-branch test: FAILS as expected (manifest field + hook file absent on upstream/main until fix(langfuse): chown postgres/clickhouse data dirs to image uids on Linux #1040 lands)
• Combined-state test (apply gh pr diff 1040 | git apply locally, run tests, revert): both new tests PASS cleanly; revert leaves worktree pristine
• Existing test classes (TestResolveHook ×7, TestCheckBashVersion ×3, TestHookEnvAllowlist ×1): 11 / 11 still pass — no regression

Manual (operator after #1040 merges):

1. git fetch upstream && git rebase upstream/main — should be a clean fast-forward / mechanical merge with no conflicts (this PR only modifies test_hooks.py; fix(langfuse): chown postgres/clickhouse data dirs to image uids on Linux #1040 does not touch that file)
2. pytest dream-server/extensions/services/dashboard-api/tests/test_hooks.py::TestLangfuseManifestHook -v → both tests PASS
3. (Adversarial) Rename hooks/post_install.sh to hooks/postinstall.sh and re-run → second test fails with the actionable diagnostic message

Review

Critique Guardian APPROVED (post-warning-fix re-review). The two warnings from the first CG pass — stale "PR #1040" mentions in source and missing .get() defensive style — were both addressed before commit.

Platform Impact

Platform	Impact
macOS / Linux / Windows (WSL2)	Pure pytest. CI runs on Linux. Test logic platform-neutral (Path manipulations + YAML parse).

[yasinBursali]

MUST MERGE AFTER #1040. This PR's tests assert that langfuse/manifest.yaml declares service.setup_hook and that langfuse/hooks/post_install.sh exists — both added by #1040. Tests fail on bare upstream/main until #1040 lands. Rebasing post-#1040 is mechanical (no file overlap).

[Lightheartdevs]

Audit follow-up: keep draft / stack on the implementation.

The structural guard is useful, but this branch currently asserts that the Langfuse hook implementation already exists while the branch does not include it. Please retarget/stack this on the PR that adds the hook file and service.setup_hook, or include the implementation here so the tests pass on the branch itself.

[Lightheartdevs]

This is still draft and still red on its own branch. I re-ran the focused hook tests locally:

python -m pytest dream-server/extensions/services/dashboard-api/tests/test_hooks.py -q

Result: 2 failed, 11 passed. The two new assertions fail because this branch does not include the Langfuse service.setup_hook = hooks/post_install.sh manifest change or the extensions/services/langfuse/hooks/post_install.sh file. That means the PR adds a regression guard for a fix that is not present in the branch.

Please stack/rebase this after the Langfuse hook implementation is merge-ready, or include the implementation here, then undraft and rerun the API job. As-is it cannot merge because it intentionally redlines CI.