fix(expressions): accept a bare true / false as an AND / OR / NOT operand

[jackylee-ch]

Rationale for this change

The BooleanLiteral to AlwaysTrue/AlwaysFalse conversion is attached to the whole expression, so a bare boolean used as an operand reaches And/Or/Not as a BooleanLiteral and fails pydantic validation. The two spellings of the same filter disagree:

parse("(false) or foo = 1")  # EqualTo(foo, 1)
parse("false or foo = 1")    # ValidationError: 1 validation error for Or

Seeding a filter with true and appending clauses is a common way to build one, so row_filter="true and status = 'x'" raises instead of scanning.

The parenthesized form works by accident: infix_notation returns the same Forward that a parenthesized sub-expression recurses through, so the fold runs only when an operand happens to take that path. Attaching it to predicate instead folds every operand. literal and literal_set consume the boolean further in, so foo = true and foo in (true, false) keep the raw BooleanLiteral. The top-level attachment is then unreachable and is removed.

Are these changes tested?

Yes, test_boolean_as_operand covers and/or/not in both positions, and test_boolean_as_literal_is_unchanged pins foo = true and foo in (true, false). The seven operand cases fail without the change; the literal case passes either way.

Are there any user-facing changes?

Filters using a bare true/false as an operand parse instead of raising.

[Copilot]

🟢 Approval recommended

The change is narrowly scoped, aligns with existing AlwaysTrue/AlwaysFalse absorption logic, and is covered by targeted new tests.

Pull request overview

This PR updates the expressions parser so that a bare true/false token used as an operand to and/or/not is folded into AlwaysTrue/AlwaysFalse during parsing, avoiding pydantic validation failures while preserving boolean literals inside comparisons and IN lists.

Changes:

• Introduce a dedicated boolean grammar element for operand positions that folds to AlwaysTrue/AlwaysFalse.
• Adjust the parser’s predicate rule to use the folded-boolean element instead of the literal-boolean element.
• Add tests covering boolean operands in and/or/not, and pin behavior for foo = true / foo in (true, false).

File summaries

File	Description
pyiceberg/expressions/parser.py	Adds a separate boolean operand parse element and uses it in predicate so And/Or/Not receive valid BooleanExpression operands.
tests/expressions/test_parser.py	Adds regression tests to ensure bare boolean operands parse and boolean literals in comparisons/sets remain unchanged.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

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[Fokko]

I'm okay widening this, thanks @jackylee-ch. I left one comment which I think we might want to clean up

[Fokko]

Thanks for adding this @jackylee-ch

[jackylee-ch]

@Fokko, the integration failure occurs while building the Hive image: apt-get update rejects an expired Debian security repository Release file, before the integration tests run. This appears unrelated to the changes in this PR. Could you please rerun the failed jobs, or let me know if any action is needed on my side?