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ast: Populate _field_types with real type objects - #6981

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youknowone merged 2 commits into
RustPython:mainfrom
youknowone:ast
Feb 3, 2026
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ast: Populate _field_types with real type objects#6981
youknowone merged 2 commits into
RustPython:mainfrom
youknowone:ast

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@youknowone

@youknowone youknowone commented Feb 3, 2026 •
edited by coderabbitai Bot
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  • Add FieldType enum and FIELD_TYPES static table mapping all AST node classes to their ASDL field types
  • Resolve markers to real Python type objects (GenericAlias, Union, plain types) at module init in populate_field_types()
  • Set class-level None defaults for optional fields
  • Replace hardcoded LIST_FIELDS and class-name checks in slot_init with _field_types-based lookup
  • Add expr_context default to Load(), fix ImportFrom.level default (now None instead of 0)
  • Fix class_getitem None check, compile() formatting

Summary by CodeRabbit

  • Refactor
    • Improved internal handling of AST field type resolution and default value assignment to enhance maintainability and flexibility in the runtime environment.

@youknowone
Populate _field_types with real type objects
2f70979 
- Add FieldType enum and FIELD_TYPES static table mapping all
  AST node classes to their ASDL field types
- Resolve markers to real Python type objects (GenericAlias,
  Union, plain types) at module init in populate_field_types()
- Set class-level None defaults for optional fields
- Replace hardcoded LIST_FIELDS and class-name checks in
  slot_init with _field_types-based lookup
- Add expr_context default to Load(), fix ImportFrom.level
  default (now None instead of 0)
- Fix __class_getitem__ None check, compile() formatting
- Remove 14 @expectedfailure decorators from test_ast
@coderabbitai

coderabbitai Bot commented Feb 3, 2026 •
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πŸ“ Walkthrough

Walkthrough

This PR refactors the AST field initialization system by introducing a type-driven approach. It adds a FieldType enum, a FIELD_TYPES constant enumerating AST class fields, and a populate_field_types function to dynamically resolve and populate _field_types attributes on AST classes at module initialization, replacing prior hard-coded defaulting logic.

Changes

Cohort / File(s) Summary
AST Type Metadata Infrastructure
crates/vm/src/stdlib/ast/pyast.rs		 Introduces FieldType enum to categorize field types (Node, Builtin, ListOf, Optional, etc.), adds FIELD_TYPES constant with per-class field metadata, and implements populate_field_types function that resolves builtin types, AST node references, and constructs generic aliases and unions for list and optional fields, then populates _field_types attributes at runtime.
Field Defaulting Logic
crates/vm/src/stdlib/ast/python.rs		 Replaces per-node hard-coded defaults with field-type-driven approach using _field_types metadata; now applies empty list defaults for list fields, None for optional fields, Load context for expression contexts, and skips defaults otherwise.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

  • #6011: Modifies AST node initialization logic in the same python.rs file; introduces custom Constructor for NodeAst which overlaps with the field defaulting mechanism refactored in this PR.

Poem

🐰 Hops with delight...

Field types now dance in metadata's glow,
No more hard-coded defaults we sow,
Types resolve at runtime, a structured way,
Lists, optionals, nodesβ€”all here to stay!
The AST now speaks the language so true. 🌿✨

πŸš₯ Pre-merge checks | βœ… 2 | ❌ 1
❌ Failed checks (1 warning)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
βœ… Passed checks (2 passed)
Check name Status Explanation
Description Check βœ… Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check βœ… Passed The title 'ast: Populate _field_types with real type objects' accurately and concisely summarizes the main change: implementing the populate_field_types() function that resolves AST field type annotations to actual Python type objects at runtime.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

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@youknowone
youknowone marked this pull request as ready for review February 3, 2026 12:56
@github-actions

github-actions Bot commented Feb 3, 2026

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πŸ“¦ Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

[x] lib: cpython/Lib/ast.py
[x] lib: cpython/Lib/_ast_unparse.py
[x] test: cpython/Lib/test/test_unparse.py (TODO: 6)
[x] test: cpython/Lib/test/test_type_comments.py (TODO: 15)

dependencies:

  • ast

dependent tests: (48 tests)

  • ast: test_ast test_builtin test_compile test_dis test_fstring test_future_stmt test_site test_ssl test_type_comments test_ucn test_unparse
    • annotationlib: test_functools test_inspect test_reprlib test_typing
      • inspect: test_abc test_argparse test_asyncgen test_code test_collections test_coroutines test_decimal test_enum test_generators test_grammar test_ntpath test_operator test_patma test_posixpath test_signal test_traceback test_types test_unittest test_yield_from test_zipimport
    • dbm.dumb: test_dbm_dumb
    • inspect:
      • bdb: test_bdb
      • dataclasses: test__colorize test_genericalias test_pprint test_regrtest test_zoneinfo
      • importlib.metadata: test_importlib
      • rlcompleter: test_rlcompleter
      • trace: test_trace
      • xmlrpc.server: test_docxmlrpc test_xmlrpc
    • pyclbr: test_pyclbr

Legend:

  • [+] path exists in CPython
  • [x] up-to-date, [ ] outdated

@youknowone
youknowone merged commit 8d07c45 into RustPython:main Feb 3, 2026
13 checks passed
@youknowone
youknowone deleted the ast branch February 3, 2026 13:05
@coderabbitai coderabbitai Bot mentioned this pull request Aug 13, 2026
Merged
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