fix(parser): parse qualified columns in GROUP BY

[jianjindream]

Fixes #2485

Summary

Parenthesized fully qualified columns in a GROUP BY list could be parsed as
a lambda expression after a comma.

The fixed LOOKAHEAD(7) accepted the seven-token (sys.dual.dummy) prefix
before verifying the required ->. This caused the parser to enter
LambdaExpression and fail at EOF.

The lookahead now matches the explicit unparenthesized lambda form,
RelObjectName() "->". Parenthesized lambdas continue to be handled through
the regular Expression() path.

Tests

Coverage includes:

• the original Oracle GROUP BY regression from [BUG] JSQLParser Version 5.3.218: RDBMS Oracle: failing group by parsing #2485;
• a four-part qualified-column boundary case;
• unparenthesized and four-parameter lambda AST assertions;
• JSON -> and ->> AST assertions.

Validation:

• Gradle check with JDK 17
• 4,920 tests, 0 failures

[Copilot]

Pull request overview

Fixes parser ambiguity where qualified columns in GROUP BY lists could be misclassified as lambda expressions.

Changes:

• Replaces fixed-width lambda lookahead with explicit arrow matching.
• Adds qualified-column and lambda regression coverage.
• Adds JSON operator AST assertions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Review summary
src/test/java/net/sf/jsqlparser/statement/select/SelectTest.java	Adds qualified-column and JSON regression tests.
src/test/java/net/sf/jsqlparser/expression/LambdaExpressionTest.java	Adds lambda AST assertions.
src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt	Updates lambda lookahead, but requires changes to preserve comma-separated PostgreSQL JSON expressions and add regression coverage.

Suppressed comments (1)

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt:8032

• -> is also the PostgreSQL JSON extraction operator (see the PrimaryExpression JSON branch at JSqlParserCC.jjt:8424-8449). Because this alternative runs before Expression(), a valid list such as SELECT f(1, data->'key') FROM t is classified as a LambdaExpression rather than a JsonExpression; the new JSON assertions only cover a first select item and do not exercise this comma-separated path. Please add a disambiguation that preserves JSON expressions here and a regression test.

            LOOKAHEAD( RelObjectName() "->" ) expr=LambdaExpression()

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[manticore-projects]

Thank you much for fixing this, it was broken indeed (and I caused that myself).