fix(plpgsql): sync generator with committed grammar

[AlexS778]

Update the PL/pgSQL grammar generator so it matches the committed plpgsql/grammar.js for drift-sensitive rules.

• emit alias declarations before variable declarations
• emit FETCH as optional FROM plus required cursor name
• add a lightweight generator drift test for decl_statement and stmt_fetch

This prevents future regeneration from undoing the current committed grammar shape.

Summary

This PR fixes drift between the committed plpgsql/grammar.js and its generator template in script/generate-plpgsql-grammar.js.

The committed grammar already has the intended behavior. This PR moves that behavior back into the generator so future regeneration does not undo it.

Changes

Declaration ordering

Updated decl_statement generation so alias declarations are emitted before variable declarations.

This preserves the existing intended behavior where:

x ALIAS FOR old_name;

is parsed as an alias declaration rather than being confused with a variable declaration whose type name starts with ALIAS.

FETCH statement shape
Updated generated stmt_fetch from:

optional(seq($.kw_from, $.any_identifier)),
$.kw_into,

to:

optional($.kw_from),
$.any_identifier,
$.kw_into,

This matches the committed grammar and supports both:

FETCH curs INTO x;
FETCH NEXT FROM curs INTO x;

Testing

Ran lightweight generator drift tests:

node --test script/*.test.js

Result:

4/4 passed

Ran PL/pgSQL corpus tests:

cd plpgsql
../node_modules/.bin/tree-sitter test

Result:

60/60 passed

Full PostgreSQL parser regeneration was not run because this PR only updates the PL/pgSQL generator template and does not change the committed generated PL/pgSQL grammar.

It does not change the broader PL/pgSQL scanner architecture or the _sql_body handling discussed separately.

Closes #29

Summary by CodeRabbit

• Tests

  • Added test to detect drift between generated and committed grammar for PL/pgSQL parsing rules.

• Chores

  • Updated internal grammar generation script with adjusted rule ordering and token parsing logic for PL/pgSQL dialect support.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 26aafd26-b720-464b-8f86-98345a4b4da5

📥 Commits

Reviewing files that changed from the base of the PR and between 33e140f and 88d3a31.

📒 Files selected for processing (2)

• script/generate-plpgsql-grammar.js
• script/generate-plpgsql-grammar.test.js

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📝 Walkthrough

Walkthrough

This PR fixes drift between the PL/pgSQL grammar generator and the committed grammar by updating script/generate-plpgsql-grammar.js to emit correct rule ordering for alias declarations and correct token parsing for fetch statements, then adds a test to prevent future drift.

Changes

Grammar Generator Drift Fixes

Layer / File(s)	Summary
Generator fixes for decl_statement and stmt_fetch script/generate-plpgsql-grammar.js	decl_statement reorders alias declarations before variable declarations to prevent ALIAS from being misinterpreted as a type name. stmt_fetch changes from optional (kw_from any_identifier) pair to optional kw_from followed by required any_identifier, matching the committed grammar and supporting both cursor-only and cursor-with-FROM forms.
Drift detection test for grammar rules script/generate-plpgsql-grammar.test.js	New test extracts and compares exact rule text for decl_statement and stmt_fetch from both the generator template and committed grammar, detecting drift to prevent fixes from being silently lost during future grammar regeneration.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🐰 A grammar generator fixed with care,
Two rules now placed with proper flair,
Alias first, then fetch astray—
Tests ensure they'll always stay! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: updating the generator script to sync with the committed grammar, addressing the core issue of generator drift.
Linked Issues check	✅ Passed	All coding objectives from issue #29 are met: alias declarations now precede variable declarations in decl_statement, stmt_fetch uses optional($.kw_from) followed by required identifier, and a drift test is added.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing generator drift: modifications to the generator template and addition of a drift detection test, with no changes to scanner or broader PL/pgSQL architecture.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[AlexS778]

@gmr Hello, found small drift between generator and grammar.