GeezerVison is showing github.com — ast: Populate _field_types with real type objects by youknowone · Pull Request #6981 · RustPython/RustPython
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youknowone
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Feb 3, 2026
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edited by coderabbitai
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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.
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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
- Remove 14 @expectedfailure decorators from test_ast
coderabbitai
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commented
Feb 3, 2026
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edited
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📝 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, nodes—all here to stay!
The AST now speaks the language so true. 🌿✨
🚥 Pre-merge checks | ✅ 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. |
✅ Passed checks (2 passed)
| Check name |
Status |
Explanation |
| Description Check |
✅ Passed |
Check skipped - CodeRabbit’s high-level summary is enabled. |
| Title check |
✅ 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.
✨ Finishing touches
🧪 Generate unit tests (beta)
- Create PR with unit tests
- Post copyable unit tests in a comment
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📦 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:
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
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youknowone
added a commit
that referenced
this pull request
Sep 16, 2026
- 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
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