Keep FOR UPDATE after LIMIT, and check formatting is a fixed point

[gmr]

Closes #67.

FOR UPDATE after LIMIT

SELECT ctid FROM t ORDER BY a LIMIT 1 FOR UPDATE SKIP LOCKED;
-- every style, v1.4.0 and main:
SELECT ctid FROM t ORDER BY a LIMIT 1;

The locking clause is lost, so a formatted job-queue worker takes no lock. After LIMIT the grammar wraps it in opt_for_locking_clause, which the clause collector did not match. It is now collected like opt_select_limit.

Fixed-point guard

The corpus writes this as FOR UPDATE LIMIT n, which #59 fixed and renders as LIMIT n FOR UPDATE, so the lock only disappeared on a second pass, which the guard never ran. formatted_corpus_is_a_fixed_point in tests/token_loss_test.rs now formats every corpus statement twice in every style and requires the same result.

It found one more case: a string constant continued across lines ('foo' then 'bar' on the next line, which PostgreSQL joins) gained seven spaces on every pass. The value was unchanged, since the whitespace sits between the parts, but the output was not stable. The parts are now joined by a bare newline and layout supplies the indentation.

The guard now checks three things over the PostgreSQL 19 documentation corpus in all 8 styles: no token loss, output re-parses, and formatting is a fixed point.

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https://claude.ai/code/session_01UFqHcQxRwX8CuJaECqiHUz

Summary by CodeRabbit

• Bug Fixes
  • Preserved FOR UPDATE SKIP LOCKED clauses when they follow LIMIT.
  • Improved formatting of PostgreSQL string literals continued across lines.
• Tests
  • Added checks for consistent formatting across styles and repeated formatting of PostgreSQL documentation examples.

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📥 Commits

Reviewing files that changed from the base of the PR and between 247d671 and 912136e.

📒 Files selected for processing (4)

• src/formatter/expr.rs
• src/formatter/select.rs
• tests/smoke_test.rs
• tests/token_loss_test.rs

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📝 Walkthrough

Walkthrough

The formatter now joins continued string literal tokens with newlines and collects locking clauses wrapped after LIMIT. Tests check both behaviors and verify fixed-point formatting across parseable corpus statements and styles.

Changes

Continued string literals

Layer / File(s)	Summary
Join continued string literal tokens src/formatter/expr.rs	format_string_const joins multiple whitespace-separated literal tokens with newlines. Single literals and inputs that do not consist only of literals remain unchanged.

Locking clauses after LIMIT

Layer / File(s)	Summary
Collect wrapped locking clauses and test formatting src/formatter/select.rs, tests/smoke_test.rs, tests/token_loss_test.rs	Clause collection now handles a locking clause nested in opt_for_locking_clause. Regression tests check FOR UPDATE SKIP LOCKED after LIMIT, string-continuation idempotence, and fixed-point formatting across corpus statements and styles.

Estimated code review effort: 2 (Simple) | ~12 minutes

Merge Risk: ⚪ Minimal · up to 91213

No concrete issue remains that would prevent merging after normal checks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes both primary changes: preserving FOR UPDATE after LIMIT and checking fixed-point formatting.
Linked Issues check	✅ Passed	The changes satisfy the coding requirements in issue #67. collect_clauses_recursive() now recognizes opt_for_locking_clause and collects its nested for_locking_clause, which preserves `FOR UPDAT…
Out of Scope Changes check	✅ Passed	The changes stay within issue #67 scope. The string-constant handling prevents repeated formatting from changing corpus output, and its regression coverage supports the required fixed-point check. The…

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_{A rabbit checks the lines of SQL,
Then joins the strings with care.
It keeps the lock after LIMIT,
And tests each style’s second pass.
One happy hop, one tidy query!}

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