juanthropic opened a new pull request, #13126:
URL: https://github.com/apache/trafficserver/pull/13126
## Summary
Adds a semantic AST and visitor for the hrw4u tool, converting
the ANTLR parse tree into typed, immutable Python dataclasses
that downstream visitors can operate on, including static
analysis, code generation, and a future user-configurable
policy linter.
The ANTLR parse tree mirrors the grammar structure, not the
domain, so every consumer must navigate intermediate rule nodes,
punctuation tokens, and context wrappers. The AST strips that
away and exposes typed, semantic nodes (e.g. `Comparison.operator`,
`IfBlock.body`). Only `ASTVisitor` needs to understand the parse
tree, so grammar changes are isolated to one file and all
downstream visitors stay insulated.
- `ast_nodes.py` — Frozen dataclasses for all hrw4u constructs:
assignments, function calls, comparisons, logical/negation
operators, if/elif/else blocks, var/use/procedure declarations,
and sections. Includes `Target` decomposition and type aliases
(`ConditionExpr`, `BodyNode`, `TopLevelNode`).
- `ast_visitor.py` — `ASTVisitor` that walks the ANTLR parse tree
and produces an `HRW4UAST`. Only `visitProgram` is overridden
from the ANTLR base; all other dispatch is internal. Raises
`ValueError` on unhandled grammar alternatives to catch
visitor-grammar drift early.
## Test plan
- `test_ast_nodes.py` — Unit tests for `Target.from_dotted`
parsing, node construction, and immutability.
- `test_ast_visitor.py` — Integration tests covering the full
source-to-AST pipeline: sections, all statement types, every
condition operator, if/elif/else nesting, real config patterns
(IP ranges, set membership, WITH modifiers, boolean coercion),
line number tracking across all 17 node types, and error
handling.
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