AfterShip / clickhouse-sql-parser / 25677835255

52%

master: 52%

Pull #269

github

Accept bare keyword as last/only SELECT item

Extend keyword-as-identifier handling to recognize end-of-statement
(EOF or `;`) as a disambiguator in expression position, so projections
like `SELECT case`, `SELECT case;`, or `SELECT limit` parse as bare
column refs — matching ClickHouse server (verified against 25.10.7.6,
which returns UNKNOWN_IDENTIFIER, i.e. syntactic accept).

The eos check is applied inline in parseColumnExpr rather than added to
keywordIsSelectItemIdentifier, because the latter is shared with the
terminator/alias-position check, where a trailing clause-starter
keyword at EOF (e.g. `SELECT * FROM`) must still be treated as a
terminator. Verified `SELECT * FROM` still errors as before.

Fixtures:
- select_keyword_as_only_column.sql        (`SELECT interval`)
- select_keyword_as_only_column_semicolon  (`SELECT case;`)
- select_clause_keyword_as_only_column     (`SELECT limit`)
- select_keyword_as_alias                  (`SELECT 1 AS interval, 2 AS from, 3 AS limit`)

The AS-alias fixture documents that `SELECT 1 AS <reserved-kw>` already
works for every reserved keyword without special handling, because
matchTokenKind(TokenKindIdent) coerces TokenKindKeyword and so
parseIdent accepts keyword tokens as alias names; added a comment at
the AS branch of parseSelectItem to make that intentional.

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