Render single spaces in ALTER visibility, FORCE and row level security actions

[minleejae]

Purpose

Follow-up to #2792. More renderers emit stray spaces. Today:

• ALTER TABLE t ALTER COLUMN c SET INVISIBLE renders SET INVISIBLE (also SET VISIBLE, and the form without COLUMN).
• ALTER TABLE t ALTER INDEX i INVISIBLE renders ALTER INDEX i INVISIBLE.
• ALTER TABLE t FORCE ends with a space, and FORCE, ALGORITHM = INPLACE renders FORCE , ALGORITHM = INPLACE.
• PostgreSQL ALTER TABLE t {ENABLE | DISABLE | FORCE | NO FORCE} ROW LEVEL SECURITY ends with a space.
• ALTER TABLE t MODIFY (c INT) renders MODIFY ( c INT ) . ADD CONSTRAINT UNIQUE KEY uk (a) renders uk (a).
• The Index of CREATE INDEX ON t (a) renders (a) when printed on its own.
• MySQL DEFAULT (JSON_ARRAY()) renders DEFAULT (JSON_ARRAY( ) ), and JSON_OBJECT() renders JSON_OBJECT( ) .

The SQL still reparses, but the extra spaces differ from the input.

Current design (As-is)

• ColumnSetVisibility appends " SET " and then " VISIBLE" or " INVISIBLE".
• Index puts two spaces before its trailing index spec when it has no columns. It also puts a space before the column list even when nothing precedes it.
• The general AlterExpression body appends a space after the operation keyword even when no payload follows. The row level security keywords add the same space.
• A bracketed single column definition is wrapped in " ( " and " ) ". The ADD CONSTRAINT <type> <name> header ends with a space before the column list's own separator.
• JSON_ARRAY and JSON_OBJECT always open with "( " and close with ") " or " ) ", even with no arguments.

Target design (To-be)

• Separate these words with exactly one space and add no leading or trailing space:
  • ALTER COLUMN c SET INVISIBLE, ALTER INDEX i INVISIBLE, FORCE and ... ROW LEVEL SECURITY;
  • MODIFY (c INT), ADD CONSTRAINT UNIQUE KEY uk (a);
  • an Index with no declaration renders (a).
• JSON_ARRAY() and JSON_OBJECT() render without inner spaces. No space follows the closing parenthesis. Calls with arguments keep their current inner spacing.
• The legacy EXCHANGE PARTITION ... WITH VALIDATION rendering of a plain AlterExpression drops its trailing space.
• Rendered SQL is otherwise unchanged. The SQL renderer and StatementDeParser produce the same text. The grammar is unchanged.

Validation

• DeparseWhitespaceTest (added in Render single spaces in DROP PRIMARY KEY, RENAME TABLE and indexes #2792) now also:
  • compares toString() and StatementDeParser output exactly for the forms above in MySQL, PostgreSQL and default mode;
  • checks that JSON_ARRAY/JSON_OBJECT with arguments or ON NULL clauses render no double space;
  • checks ColumnSetVisibility, a constructed Index and a constructed EXCHANGE PARTITION action directly.
• No existing assertion encoded these spaces, so no existing test changed.
• Java 17 offline Gradle spotlessApply check: 10,382 tests, 10,357 passed, 25 skipped, zero failures/errors.
• Compared with master (bdf8ac31) on a corpus of 635 MySQL 8.4 and PostgreSQL 18 DDL/DCL statements, each accepted by the server, with and without a dialect: no regressions. Only 6 MySQL and 3 PostgreSQL statements of the forms above change their toString(), in both dialect and default mode. In CREATE INDEX ON ..., the contained index renders (name) instead of (name).
• MySQL 8.4 and PostgreSQL 18.3: every corpus statement this branch parses ran as written on one server and as rendered by toString() on a second, identical server, in the same order. All 205 MySQL and 328 PostgreSQL statements give the same result (success, or the same error).

Integration validation

Applied #2806–#2819 together on master (bdf8ac31), with the stacked PRs on top of their bases (#2806 → #2807 → #2808, #2806 → #2809 → #2810 and #2811 → #2812).

• Each branch merges cleanly into master. Between the branches, conflicts are limited to adjacent additions (README/index rows, usage sections, imports, visitor and feature lists, one enum line and one alias guard).
• The integrated build passes Java 17 offline Gradle spotlessApply check: 11,494 tests, 11,469 passed, 25 skipped, zero failures/errors. The grammar choice conflict check passes.
• On a corpus of 635 MySQL 8.4 and PostgreSQL 18 DDL/DCL statements, each accepted by the server, the integrated build parses 265 of 271 MySQL statements (master: 206) and 363 of 364 PostgreSQL statements (master: 328). Every MySQL 8.4 non-reserved word and PostgreSQL 18 unreserved or column-name keyword parses as a column and table name.
• On paired MySQL 8.4 and PostgreSQL 18.3 servers, all 263 MySQL and 362 PostgreSQL statements rendered by the integrated build give the same results as the originals.