peter
b1832afd18
Mechanical, whole-tree `ruff format` pass — no behaviour change. Recorded in .git-blame-ignore-revs (next commit) so git blame skips it.
79 lines
3.4 KiB
Python
79 lines
3.4 KiB
Python
"""Migration hygiene (TEST-3), DB-lane.
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Two things the prod boot never checks:
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- **model <-> schema drift:** `entrypoint.sh` only ever runs `alembic upgrade head`; nothing verifies the
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migrated schema still matches `Base.metadata`. A model column added without a migration (or a migration
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that drifted from the model) ships silently.
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- **the downgrade path:** every migration defines `downgrade()`, but it never runs, so a broken downgrade
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is only discovered during an emergency rollback.
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Both use the `db` fixture, which has already brought the schema to head via `_schema`.
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Scope note: we gate on COLUMN/TABLE drift — a table or column present on one side and not the other, or
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a column whose type/nullability disagrees. `compare_metadata` also reports index/constraint/sequence
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differences, but those are dominated by migration-only objects (partial/expression/GIN indexes, CHECK
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constraints, SERIAL sequences) that can't be expressed on `Base.metadata`, so comparing them wholesale is
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noise; they're filtered out. The column/table signal is the "someone changed a model without a migration"
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case worth failing on.
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"""
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from alembic import command
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from alembic.autogenerate import compare_metadata
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from alembic.config import Config
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from alembic.migration import MigrationContext
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from app.db import Base, engine
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# The diff ops that mean a real table/column disagreement (presence AND shape) — not the index/
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# constraint/sequence noise from migration-only objects.
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_DRIFT_OPS = {
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"add_table",
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"remove_table",
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"add_column",
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"remove_column",
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"modify_type",
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"modify_nullable",
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}
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def _structural_drift():
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"""Table/column presence diffs between the ORM models and the migrated schema (`compare_type=True`
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mirrors alembic/env.py). compare_metadata nests per-column ops in a sub-list per table and returns
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table-level ops as bare tuples; flatten both and keep only the presence ops."""
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with engine.connect() as conn:
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ctx = MigrationContext.configure(conn, opts={"compare_type": True})
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diffs = compare_metadata(ctx, Base.metadata)
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drift = []
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for d in diffs:
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for entry in d if isinstance(d, list) else [d]:
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if isinstance(entry, tuple) and entry and entry[0] in _DRIFT_OPS:
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drift.append(entry)
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return drift
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def test_models_match_the_migrated_schema(db):
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# Non-empty == the ORM models and the alembic-built schema disagree on a table/column — almost
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# always a model change that forgot its migration.
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drift = _structural_drift()
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assert drift == [], "model/schema drift — add or fix a migration:\n" + "\n".join(
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str(d) for d in drift
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)
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def test_head_migration_downgrades_and_reupgrades(db):
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# Exercise the newest migration's downgrade + re-upgrade so a broken downgrade is caught the sprint
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# it lands, not during a rollback. Leaves the schema back at head for the rest of the session.
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cfg = Config("alembic.ini")
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command.downgrade(cfg, "-1")
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reupgraded = False
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try:
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command.upgrade(cfg, "head")
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reupgraded = True
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assert _structural_drift() == []
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finally:
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# If the re-upgrade itself failed, restore the SHARED schema to head so the failure doesn't
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# cascade into every later DB-lane test. Skip it when the upgrade already succeeded — re-running
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# it would be a redundant no-op and could mask a failing assert with the finally's own error.
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if not reupgraded:
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command.upgrade(cfg, "head")
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