fix(OMN-16692): a psql that did not run must fail loudly, not read as schema drift

[jonahgabriel]

OMN-16692 — a psql that did not run must never be read as schema drift

tests/integration/migrations/test_node_migration_shape_drift_omn15376.py asserted directly on psql stdout at four sites. A psql that did not run — binary missing or broken, server unreachable, permission error, ON_ERROR_STOP abort — exits non-zero with empty stdout, so those asserts turned a missing prerequisite into a content mismatch that reads as real schema drift. That is exactly what the 2026-08-26 runner-class flip surfaced in the Migration Integration Test job: the log printed psql client unavailable, and the test then failed with

assert '' == 'delegation_routing_tenant_overlay_pkey:p,delegation_routing_tenant_overlay_tenant_task_uq:u'

The missing-returncode-check predates the flip; the flip only routed the job somewhere psql was not guaranteed. It will recur on any future runner-class change.

Fix

One helper, used for every read of psql output:

def _psql_stdout(result: subprocess.CompletedProcess[str], what: str) -> str:
    assert result.returncode == 0, (
        f"psql did not run successfully ({what}): exit {result.returncode}. "
        f"This is a missing/failed prerequisite, NOT schema drift.\n"
        f"stdout={result.stdout!r}\nstderr={result.stderr!r}"
    )
    return result.stdout.strip()

Sites converted:

Site	Before
delegation_routing_tenant_overlay constraint probe (ticket :875)	assert constraints.stdout.strip() == (...) — no returncode check
delegation_routing_tenant_overlay shape probe (ticket :855)	assert shape.stdout.strip() == "0|0|..." — no returncode check
column-presence probe in the GREEN test	assert present.stdout.strip() == "1" — no returncode check
row-count probe in the row-preservation test	assert rows.stdout.strip() == "2" — no returncode check
_schema_snapshot	already checked returncode; now routed through the same helper so there is one reader
pg_roles probe in _new_database	if "1" not in exists.stdout — a failed probe silently decided "role missing" and moved on

Assertion messages still print the raw stdout, so a genuine content mismatch reads exactly as before. Two guard tests cover the helper directly (pure CompletedProcess, no Postgres), living in this module for the same reason the OMN-16412 host guards do — the whole file is skipped at import when psql is unavailable.

Evidence — the module run both with and without psql

Local Postgres path: no ambient OMNIBASE_INFRA_DB_URL/POSTGRES_HOST, so the suite built its own ephemeral cluster from local initdb.

1. psql present (baseline, full module)

$ env -u OMNIBASE_INFRA_DB_URL -u POSTGRES_HOST uv run pytest \
    tests/integration/migrations/test_node_migration_shape_drift_omn15376.py -p no:randomly -n 0 -q
25 passed, 3 warnings in 26.52s

2. psql absent — no OMN15376_REQUIRE_PG → explicit skip with a reason

$ env -u OMNIBASE_INFRA_DB_URL -u POSTGRES_HOST PATH=/usr/bin:/bin:/usr/sbin:/sbin \
    python -m pytest ... -p no_psql_plugin -rs -q
SKIPPED [1] test_node_migration_shape_drift_omn15376.py:132: psql not available
1 skipped, 3 warnings in 0.10s

3. psql absent — OMN15376_REQUIRE_PG=1 → hard failure at collection, no vacuous green

$ ... OMN15376_REQUIRE_PG=1 python -m pytest ... -p no_psql_plugin -q
E   AssertionError: OMN15376_REQUIRE_PG=1 but psql is not available
ERROR tests/integration/migrations/test_node_migration_shape_drift_omn15376.py

Note on the shim: a bare PATH strip does not simulate absence on a Homebrew box, because _pg_bin() falls back to a hardcoded /opt/homebrew/opt/postgresql@*/bin lookup. The absence runs therefore used a small pytest plugin that blinds both lookups (shutil.which → None for psql/initdb/pg_ctl, and an empty glob for /opt/homebrew/opt) in addition to the PATH strip — otherwise runs 2 and 3 would have quietly found psql anyway and proven nothing.

4. The actual defect, RED → GREEN. A psql wrapper that passes through for every call except the constraint probe, where it exits 2 with empty stdout — i.e. psql present but the invocation failing, the case a module-level skip cannot catch:

# pre-fix (this file at origin/dev)
E   AssertionError: assert '' == 'delegation_r...ant_task_uq:u'
E     - delegation_routing_tenant_overlay_pkey:p,delegation_routing_tenant_overlay_tenant_task_uq:u
1 failed

# post-fix, identical shim
E   AssertionError: psql did not run successfully (delegation_routing_tenant_overlay constraint probe):
E     exit 2. This is a missing/failed prerequisite, NOT schema drift.
E     stdout=''
E     stderr='psql: error: connection to server was lost\n'
1 failed

Both still fail — correctly, because the prerequisite genuinely broke — but only one of them says why.

Gates

• uv run ruff format + ruff check — clean.
• pre-commit run --all-files — all hooks Passed, no bypass, no skip token.
• mypy on the changed file: 6 errors before the change, 6 after — byte-identical set, all the pre-existing _PSQL: str | None list-item complaints on lines this PR does not touch. Nothing introduced.
• Pre-push governed selector (OMN-13973): Passed. It deferred tests/integration/migrations/ to CI as integration-scoped (the hook is unit-scoped) and reported no impacted unit tests. No PREPUSH_FULL_SUITE, no ENABLE_SMART_TESTS=off, no --no-verify.

Ticket: OMN-16692. Related: OMN-15376 (the suite), OMN-16682 / OMN-16691 (the runner flip that exposed this).

Summary by CodeRabbit

• Bug Fixes
  • Improved database migration validation to distinguish command execution failures from actual schema mismatches.
  • Error messages now provide clearer diagnostics when prerequisite database commands fail.
  • Added coverage to verify successful command handling and accurate failure reporting.

Evidence-Ticket: OMN-16692
Evidence-Source: OCC#7243

Review follow-ups

Two CodeRabbit findings landed on this PR; an auto-fix commit (a8f592a) applied both.

• Kept — command={result.args!r} in the failure message. Naming the actual invocation is squarely the point of this PR.
• Reverted in 6a3ea119b — the other half sourced ~/.omnibase/.env into os.environ inside the server fixture. That re-opens the vector OMN-16412 closed in this very module: the suite CREATEs and DROPs throwaway databases on whatever server it resolves, so an ambient OMNIBASE_INFRA_DB_URL/POSTGRES_HOST the caller never handed it is a hard error by design, and a dotenv load manufactures exactly that (and can carry OMN15376_ALLOW_REMOTE_PG=1, disarming the guard outright). It is also unrelated to OMN-16692. The refusal is now stated in the module beside the guard so it is not re-applied later; reasoning posted on the review thread.

Module re-run after the revert: 25 passed (same ephemeral-cluster path as above).

[coderabbitai]

📝 Walkthrough

Walkthrough

The migration shape-drift tests now validate psql success before interpreting output. A shared helper reports command failures with stderr and probe context. Existing role, schema, column, row-count, shape, and constraint checks use this helper.

Changes

psql probe validation

Layer / File(s)	Summary
Validated psql helper and coverage tests/integration/migrations/test_node_migration_shape_drift_omn15376.py	Added _psql_stdout and tests for failed and successful psql commands.
Migration probe integration tests/integration/migrations/test_node_migration_shape_drift_omn15376.py	Updated role, schema, column, row-count, shape, and constraint probes to validate psql execution before comparing output.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: 🔵 Low · up to 2ada4

The change makes failed database probes report prerequisite failures instead of misleading schema drift, but the test diagnostics should include the exact command and ensure the intended database environment is loaded; the PR is mergeable with explicit owner follow-up on those bounded risks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly describes the main fix: failed psql executions must produce explicit failures instead of being misreported as schema drift.

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

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[coderabbitai]

Actionable comments posted: 2

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Inline comments:
In `@tests/integration/migrations/test_node_migration_shape_drift_omn15376.py`:
- Around line 487-490: Update the failure message in the return-code assertion
to include the executed psql invocation via result.args, alongside what, exit
code, stdout, and stderr. Extend the guard test to assert that the command
detail is present in the reported failure message.
- Line 552: Update the test setup before the database probes so it loads
~/.omnibase/.env before server invokes _psql or _psql_script, including the
pg_roles probe around _psql_stdout. Preserve the existing probe behavior after
the environment is loaded.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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✅ Hostile Reviewer — PASSED

Blocking findings (critical): 0
Total findings: 0
Models succeeded: qwen3-review,qwen3-review-b

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Verdict	Meaning	Blocks merge?
passed	No critical findings	No
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degraded	All models unavailable (infra)	No (pilot)

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