feat: PostgreSQL 18 support (libpg-query 18.1.1, @pgsql/types 18)

[pyramation]

Summary

Upgrades the whole monorepo to PostgreSQL 18: libpg-query@18.1.1 + @pgsql/types@^18.0.0 everywhere (SQL side and PL/pgSQL side — the plpgsql packages switch from @libpg-query/parser@17 to libpg-query, whose slim API now includes parsePlPgSQL).

Release strategy (no publish in this PR): publish PG18 packages under the pg18 npm dist-tag, keeping pg17 as latest for now — mirroring the 16→17 rollout. config/versions.json adds the 18 entry (libpg-query 18.1.1, pgsql-parser/pgsql-deparser 18.0.0, npmTag: pg18).

Deparser (pgsql-deparser)

• returningList → returningClause: new ReturningClause / ReturningOption visitors on INSERT/UPDATE/DELETE/MERGE, incl. RETURNING WITH (OLD AS o, NEW AS n).
• New ATAlterConstraint node: ALTER TABLE ... ALTER CONSTRAINT c [NOT] ENFORCED | [NOT] DEFERRABLE [INITIALLY DEFERRED] | [NO] INHERIT.
• Constraint: is_enforced (NOT ENFORCED), generated_kind (GENERATED ... VIRTUAL), without_overlaps / pk_with_period / fk_with_period (temporal PK/FK with WITHOUT OVERLAPS / PERIOD), CONSTR_NOTNULL, CONSTR_ATTR_[NOT_]ENFORCED; removed obsolete AT_CheckNotNull.
• CreateStmt.nnconstraints, IndexStmt.iswithoutoverlaps, new MergeSupportFunc (merge_action()).
• PG18 VariableSetStmt.jumble_args used to preserve special SET TIME ZONE ... / SET XML OPTION ... spellings.
• New location-only fields (rexpr_list_start/end, list_start/list_end, …) added to fixture-cleaning utils.

Transform (@pgsql/transform)

• New src/18 types/enums, transformers/v17-to-v18.ts, direct transformers v13..v17-to-v18, multi-version registry updated; transformToLatest now targets 18.
• v17→v18 handles returningList→returningClause, wraps AT_AlterConstraint defs in ATAlterConstraint, and sets jumble_args for VAR_SET_MULTI TRANSACTION forms.
• Fixed latent transformer bugs surfaced by the new end-to-end (13→18) flow: v16→v17 MergeWhenClause.matched→matchKind, v13→v14 AlterExtensionContentsStmt objfuncargs handling.
• Kitchen-sink fixtures regenerated for all version pairs (1437 tests green); irrecoverable cross-version ambiguities (e.g. PG17 AST can't distinguish SET TIME ZONE from SET timezone TO) documented in skip-tests/known-issues.ts.

PL/pgSQL packages (plpgsql-parser / plpgsql-deparser / plpgsql-parse / parse)

Switched to libpg-query@18.1.1. PG18's PL/pgSQL serialization changed in ways the deparser now handles:

• out_param_varno is no longer serialized when 0 → new resolveOutParamVarno() (finds the (unnamed row) OUT-param datum, falls back to returnInfo), so RETURN; / RETURN NEXT; are still suppressed correctly in OUT-param functions.
• RETURN NEW now arrives as retvarno instead of expr text → deparse emits RETURN NEW/RETURN OLD (uppercase; source casing is not recoverable).
• PLpgSQL_rec now carries datatype (source-cased, e.g. record vs RECORD) → declarations preserve it; %rowtype/%type suffix casing normalized.
• generated.json regenerated: 27 fixtures skipped where PG18 rejects them at parse time (PG18 now validates e.g. RETURN expr in procedures, OUT+VARIADIC, unknown domain-array return types, %type[]); snapshots updated for the casing changes above.

Fixture churn categories

1. New PG18 fixtures (__fixtures__/kitchen-sink/misc/pg18.sql, transform 17-18 suites).
2. Regenerated kitchen-sink/transform fixtures from the new proto (field additions only).
3. PL/pgSQL snapshot updates: record-case preservation and RETURN NEW/new casing.
4. Skipped PL/pgSQL fixtures that PG18 rejects at parse time (listed above).

Not supported / known limits

• v17→v18 transformer cannot reconstruct jumble_args for special SET TIME ZONE / SET XML OPTION (info missing from PG17 AST) — documented as known issues.
• pgsql-types and @pgsql/cli have no test files (jest exits "No tests found") and repo-wide pnpm run lint fails on ESLint 9 vs .eslintrc — both pre-existing on main, untouched here.

Verification

pnpm run build green; all package test suites green: deparser 714, transform 1437, plpgsql-deparser 106, plpgsql-parser 285, plpgsql-parse 57, parse 68, parser 9, quotes 57, traverse 12, utils 4, proto-parser 42.

Link to Devin session: https://app.devin.ai/sessions/064ad193e1c040af8c145d55e07af9b8
Requested by: @pyramation

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​pgsql/​enums@​18.0.0
	@​pgsql/​types@​18.0.0
	libpg-query@​18.1.1

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