fix: function type generation for zero arg and scalar computed fields - #1035

… Args, trigger-writable views (#125)

## Summary

Ports the worthwhile TypeScript generator fixes from postgres-meta's
open template PRs into this package (the templates are being deleted in
favor of this package in supabase/postgres-meta#1084, so open fixes
there are triaged and re-landed here). Four fixes, one commit each:

1. **Stored generated columns omitted from Insert/Update** (from
supabase/postgres-meta#1105): `GENERATED ALWAYS AS ... STORED` columns
reject writes in Postgres, but only identity-ALWAYS columns were
excluded; both now emit `?: never`.
2. **Non-nullable json narrowed to `NonNullable<Json>`** (from
supabase/postgres-meta#1085): the emitted `Json` type includes `null`,
so a NOT NULL json/jsonb column structurally permitted null. Known
accepted edge: a NOT NULL jsonb column holding a JSON `'null'::jsonb`
value still serializes as JS `null`, so Row is optimistic in that case;
Insert/Update narrowing is fully sound.
3. **Zero-argument function Args typed `Record<PropertyKey, never>`**
(the still-valid half of supabase/postgres-meta#1035): `Args: never`
makes postgrest-js treat every zero-argument function as a computed
field (`never extends { '': Row }` always holds), dropping same-named
columns from `select('*')` results, and an uninhabited `Database` breaks
sound type tooling. Verified against postgrest-js, whose
`IsMatchingArgs` special-cases `Record<PropertyKey, never>`.
4. **Insert/Update types for INSTEAD OF trigger views** (from
supabase/postgres-meta#1062, reimplemented): views made writable by
INSTEAD OF triggers got no Insert/Update types. Views now carry
`is_insert_enabled`/`is_update_enabled` computed via
`pg_relation_is_updatable(oid, true)` (bit 8 INSERT, bit 4 UPDATE; also
covers INSTEAD rules), gated independently, and column updatability
counts triggers too (`pg_column_is_updatable(oid, attnum, true)` plus an
explicit INSTEAD OF INSERT trigger check, since that function only
considers the UPDATE event). The origin PR duplicated hand-rolled
pg_trigger subqueries with one pair of wrong bit values and left
trigger-writable columns degrading to `?: never`, visible in its own
snapshot. The two new `PostgresView` fields are additive (metadata
version stays 1), documented, and mirrored in the frozen equivalence
contract.

## Triage of origin PRs

| postgres-meta PR | Verdict | Reasoning |
|---|---|---|
| #1105 | Ported | Two-line correctness fix; `is_generated` was already
introspected. |
| #1085 | Ported | Nullability chokepoint fix; function returns and
composite attributes untouched. |
| #1035 | Ported (zero-arg half) | The computed-field-filtering half is
superseded: this package introspects with `includeTableTypes: true`, so
table/view row types already resolve (parity golden shows computed
fields working). Only foreign-table row types remain uncovered; the PR's
name-string matching is too fragile to port for that niche. |
| #1062 | Reimplemented | Right idea, broken execution (wrong tgtype
bits in one duplicated subquery pair, all-`never` Update output in its
own snapshot). |
| #1063 (TS part) | Skipped | Superseded: composite attributes already
emit `| null` on main; the PR's remaining delta (`unknown | null`) is
the identical type. |
| #1048 (vector to `number[]`) | Skipped | Wrong as a global remap:
PostgREST serializes pgvector as strings in responses, so Row types
would regress; the reviewer asked for e2e evidence and got none. Needs
input/output-aware mapping, a design discussion. |
| #973 (`| string` numeric inserts) | Skipped | Maintainer requested
changes: breaking for consumers expecting `number`; per-column overrides
are the escape hatch. |
| #573 | Skipped | Blanket `| null` on function args/returns is breaking
(author concedes); the centralization half is superseded by the current
generator; the domain-resolution gap is real but needs a metadata
contract extension (feature-scale, raised separately). |
| #750 (`Json` to `unknown`) | Skipped | Breaking; major-version
decision. |
| #1044 (int8 to `bigint`) | Skipped | Breaking, and incorrect without a
custom JSON parser. |
| #1083 (`bigint_as` option) | Skipped | Feature/option with API design
questions, not a fix. |
| #814 (json_schema constraint types) | Skipped | New feature. |

## Validation

- Unit tests per fix, plus Docker-backed introspection integration tests
proving a join view with an INSTEAD OF INSERT trigger introspects as
insert-enabled/update-disabled with updatable columns, and
auto-updatable views keep both flags.
- Parity golden regenerated and reviewed line by line: the only change
is 14 zero-argument functions switching `Args: never` to `Args:
Record<PropertyKey, never>`. Fixes 1, 2 and 4 have no fixture-visible
effect.
- `check-types`, `format-and-lint`, `knip`, `build`, `test` (99 pass
across 12 files) all green.
- Note: the nightly parity job against real postgres-meta will show this
intentional drift until postgres-meta consumes a release containing it
(supabase/postgres-meta#1084 replaces the templates with this package,
closing the gap).