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009ac9f9eff96c8fb69d642c110f7aeaba58edbb
shopdb-flask/docs/adr/ADR-008-plugin-migration-ownership.md
cproudlock 22e623c1f6 Plugin framework maturation, reports overhaul, theming, and USB frontend repair 
Framework:
- Per-plugin Alembic migration chains (ADR-008): every bundled plugin
  carries its own chain with a stamp-only anchor at the ownership cutover;
  new plugin schema lands in plugins/<name>/migrations/, never the core
  chain. Deploys add flask plugin upgrade-all. Fixed a latent bug in the
  shared alembic template (engine URL resolution) and taught the metadata
  filter to include FK-referenced core tables.
- Frontend plugin route gating (ADR-009): plugin routes carry meta.plugin;
  a disabled plugin's pages redirect to the dashboard via a cached,
  fail-open check against the new public GET /api/plugins/enabled.
- get_reports() plugin hook (contract 0.5.0 -> 0.6.0): plugins contribute
  report cards; warranty and toner cards moved off the hardcoded list.

Reports:
- Hub grouped by category with search; inline reports render at the top,
  are URL-backed (?report=id, back-button and deep links work), expose
  their server-side filter params as controls, and export CSV. Warranty
  and Toner pages gained CSV export.
- Deleted the dead legacy Warranty Status report (always-zero buckets
  from a retired column).

Theming and fonts:
- Inter (variable) bundled locally via @fontsource, replacing the Google
  Fonts Roboto import - air-gapped installs now render correctly; tables
  use tabular numerals.
- Optional brand_primary_dark_color, brand_accent_color,
  brand_sidebar_color settings applied to CSS vars at bootstrap.

USB frontend repair (views were reading a dead legacy shape):
- List/detail/form and the employee profile USB panels remapped to the
  real API shape (device_id/device_desc/checkinoutlog); employee panels
  now use /usb/checkouts endpoints; external-mode /usb/checkouts/active
  honors the badge filter; dead client methods pruned.

Also: warranties list page no longer requires login (matches app
convention); collector doc rewritten with a GE-Enforce integration guide
and paste-ready PowerShell reporter; ADR index and CHANGELOG updated.

Verified: 323 tests pass, naming/style green, frontend builds, plugin
migration dry-run green on scratch MySQL.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-11 10:01:47 -04:00

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# ADR-008: Plugin migration ownership (per-plugin chains from the cutover)
- **Status:** ACCEPTED
- **Date:** 2026-07-10
- **Deciders:** cproudlock
- **Supersedes:** the "Migration strategy (resolved)" section of ADR-004
## Context
ADR-004 resolved a Phase 7B footgun by folding every bundled plugin's tables
into the single core Alembic chain (migration `7c04_fold_plugin_schema`), and
later core migrations (`7d04`..`7d16`) kept adding plugin schema directly to the
core chain. At the time this was the safe choice: bundled-plugin baselines and
the core baseline had both been creating the same tables, so
`flask plugin upgrade-all` would collide with `flask db upgrade`.
That resolution left the per-plugin Alembic engine
(`shopdb/plugins/migrations.py`, `shopdb/plugins/alembic_template.py`, the
`alembic_version_<plugin>` version tables, and `flask plugin upgrade-all`) fully
built but unused for the bundled plugins. The framework is the product (per the
project's charter); a plugin that cannot own its own schema is not really a
plugin. Sister sites that adopt or fork a plugin need its schema history to
travel with the plugin, not be entangled in the host's core chain. Keeping every
future plugin table change in the core chain also means the core chain grows
without bound and a plugin can never be cleanly removed.
The blocker ADR-004 worried about (double table creation) only exists while a
plugin's own migration tries to CREATE tables the core chain already created.
That is avoidable: history is immutable, so the tables already built by the core
chain stay owned by the core chain; only NEW schema needs a new home.
## Decision
Ownership splits at a fixed cutover, the current core-chain head.
1. **Core chain owns history through its head.** The core Alembic chain
(baseline `68b3947ae14f` .. head `7d16_directoryemployees`) remains
authoritative for every table that exists at the cutover, including the
bundled-plugin tables it created. Those migrations are immutable and are not
rewritten. `flask db upgrade` continues to reproduce the full schema.
2. **Plugin chains own plugin schema going forward.** From the cutover forward,
any change to a plugin's schema lands as
`plugins/<name>/migrations/versions/000N_*.py` in that plugin's own chain,
never in the core chain. The core chain is reserved for core tables.
3. **Every table-owning bundled plugin gets a `0001` anchor.** Each such plugin
carries a migration chain whose first revision is a stamp-only no-op:
`upgrade()` does nothing because the core chain already created the tables.
The anchor exists so the plugin chain has a base that
`flask plugin upgrade-all` can stamp into the per-plugin version table
`alembic_version_<plugin>`. Blueprint-only plugins that own no tables get no
chain.
4. **Deploy and upgrade sequence.** A deploy runs `flask db upgrade`
(core chain, creates everything through the head) then
`flask plugin upgrade-all` (stamps every plugin anchor and applies any later
per-plugin migrations). The same two commands upgrade an existing install;
both are idempotent. The registry (`instance/plugins.json`) tracks each
plugin's applied revisions in `migrations_applied`.
5. **Table-ownership registry.** `PLUGIN_TABLE_OWNERS` in
`shopdb/plugins/alembic_template.py` is the explicit map of which tables each
plugin owns; it is kept in sync with the plugins' `__tablename__` declarations
and pinned by `tests/test_plugin_migrations.py`.
External (out-of-tree) plugins per ADR-003 already shipped their own chains;
this ADR brings the bundled plugins onto the same model, so there is one rule
for all plugins.
## Consequences
### Positive
- A plugin's schema history travels with the plugin. Adopting or forking sites
get the plugin's migrations, not a slice of someone else's core chain.
- The core chain stops accreting plugin schema; it stays about core tables.
- A plugin can be evolved (or, with its own downgrade, removed) independently.
- The long-built per-plugin Alembic engine is finally exercised on every deploy,
so it cannot silently rot.
### Negative / cost
- Two migrate commands per deploy instead of one. Documented in `docs/DEPLOY.md`
and `docs/UPGRADE.md`; both are idempotent so the cost is one extra safe call.
- A plugin author must now put new tables in the plugin chain and register them
in `PLUGIN_TABLE_OWNERS`, rather than autogenerating into the core chain. The
`flask plugin new` guidance and this ADR spell that out.
- The cutover is a discontinuity: tables created before it are core-owned,
tables created after it are plugin-owned. The line is the core-chain head at
this ADR's date, recorded here so it is unambiguous.
### Neutral
- No schema changes and no data migration: the anchors are no-ops. A fresh
install and an existing install converge to the same state.
## Alternatives considered
1. **Keep everything in the core chain (status quo per ADR-004).** Simplest
operationally but defeats the plugin-as-product goal: plugin schema cannot
travel, the core chain grows without bound, and plugins can never be cleanly
removed. Rejected.
2. **Rewrite history so plugin tables move out of the core chain into plugin
`0001` CREATE migrations.** Would make each plugin chain self-contained from
empty, but breaks the immutability rule, forces every existing site to
re-run a rewritten chain, and re-introduces the exact double-creation footgun
ADR-004 fixed. Rejected.
3. **Anchor that CREATEs tables with `IF NOT EXISTS` guards.** Lets a from-empty
install build plugin tables from the plugin chain, but then two chains both
claim the same tables and drift can diverge silently. The no-op anchor keeps
a single authoritative creator (the core chain) for cutover-era tables.
Rejected.
## References
- ADR-003 (plugin distribution; external plugins already ship chains)
- ADR-004 (deployment topology; this ADR supersedes its migration-strategy note)
- `shopdb/plugins/alembic_template.py` (`PLUGIN_TABLE_OWNERS`, shared env runner)
- `shopdb/plugins/migrations.py`, `shopdb/plugins/cli.py` (`upgrade-all`)
- `plugins/<name>/migrations/` (per-plugin chains and `0001` anchors)
- `tests/test_plugin_migrations.py` (ownership + chain + idempotency guards)
- `docs/DEPLOY.md`, `docs/UPGRADE.md`, `docs/PLUGINS.md` (deploy sequence)
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