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Raise ValueError for None in Stmt lists to match CPython validator - #7670

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youknowone merged 1 commit into
RustPython:mainfrom
changjoon-park:fix-stmt-none-disallowed
Apr 24, 2026
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Raise ValueError for None in Stmt lists to match CPython validator#7670
youknowone merged 1 commit into
RustPython:mainfrom
changjoon-park:fix-stmt-none-disallowed

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@changjoon-park changjoon-park commented Apr 24, 2026 •
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Sibling fix to #7656 (which handled Vec<Expr>). The same catch-all TypeError(\"expected some sort of stmt, but got {}\") in Stmt::ast_from_object silently swallowed None, so compile() on an AST with None in a statement-list field (ClassDef.body, Try.body, For.body, etc.) raised TypeError where CPython raises ValueError(\"None disallowed in statement list\").

Fix

One check in Stmt::ast_from_object (crates/vm/src/stdlib/_ast/statement.rs) before the catch-all, matching the Expr-side shape from #7656:

} else if _vm.is_none(&_object) {
    return Err(_vm.new_value_error(\"None disallowed in statement list\"));
}

Option<Stmt> positions are unaffected — node.rs Option<T>::ast_from_object short-circuits None earlier.

Verification

CPython 3.13.4 baseline message:

$ python3 -c \"import ast; compile(ast.Module([ast.ClassDef('X', [], [], [None], [], [])], []), '<t>', 'exec')\"
ValueError: None disallowed in statement list

After the fix, RustPython raises the byte-identical message for ClassDef, For, While, Try, and FunctionDef body positions.

Full test.test_ast.test_ast suite (227 tests):

Ran 227 tests in 18.951s
OK (skipped=10, expected failures=38)

0 failures, 0 unexpected successes. One less expected failure than upstream/main (was 39), corresponding to test_classdef unmasked.

Unmasks

  • ASTValidatorTests.test_classdef (was @unittest.expectedFailure; body=[None] sub-case now passes)

Part of the skip-test inventory in #7611.

Summary by CodeRabbit

  • Bug Fixes
    • Improved error handling for invalid statement list inputs, providing a more specific error message when None values are encountered instead of generic type errors.

@changjoon-park
Raise ValueError for None in Stmt lists to match CPython validator
64cb2fd 
Sibling fix to RustPython#7656 (which handled Vec<Expr>). The same catch-all
TypeError ("expected some sort of stmt, but got {}") in
Stmt::ast_from_object silently swallowed None, so compile() on an
AST with None in a statement-list field (ClassDef.body, Try.body,
For.body, etc.) raised TypeError where CPython raises
ValueError("None disallowed in statement list").

Add an is_none check before the catch-all, matching the Expr-side
shape introduced in RustPython#7656. Option<Stmt> positions are unaffected —
they short-circuit None earlier in node.rs.

Unmasks test_classdef (body=[None] sub-case). Full
test.test_ast.test_ast run: 227 tests, 0 unexpected successes, 38
expected failures (was 39).
@coderabbitai

coderabbitai Bot commented Apr 24, 2026 •
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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info
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Run ID: 502bbe97-f6a4-4c7c-8958-9912b5e56805

📥 Commits

Reviewing files that changed from the base of the PR and between dc0c814 and 64cb2fd.

⛔ Files ignored due to path filters (1)
  • Lib/test/test_ast/test_ast.py is excluded by !Lib/**
📒 Files selected for processing (1)
  • crates/vm/src/stdlib/_ast/statement.rs
📝 Walkthrough

Walkthrough

The PR enhances the ast_from_object function for ast::Stmt to explicitly validate and reject None values in statement lists. When None is encountered during statement-list conversion, it now raises a specific ValueError with message "None disallowed in statement list" rather than producing a generic type error.

Changes

Cohort / File(s) Summary
AST Statement Validation
crates/vm/src/stdlib/_ast/statement.rs		 Enhanced ast_from_object with an explicit is_none check that raises a specific error for None values in statement lists, improving error clarity and validation specificity.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Possibly related PRs

Suggested reviewers

  • ShaharNaveh

Poem

🐰 A little check, so swift and clean,
"No None!" our statement guard does deem,
With error crisp and message bright,
The AST lists stand firm and right! ✨

🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly and specifically describes the main change: raising a ValueError for None in statement lists to match CPython's behavior.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.

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@github-actions

github-actions Bot commented Apr 24, 2026

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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
[ ] test: cpython/Lib/test/test_type_comments.py (TODO: 15)

dependencies:

  • ast

dependent tests: (136 tests)

  • ast: test_ast test_builtin test_compile test_compiler_codegen test_dis test_fstring test_future_stmt test_site test_ssl test_type_comments test_ucn test_unparse
    • annotationlib: test_annotationlib test_functools test_inspect test_reprlib test_type_annotations test_type_params test_typing
      • dataclasses: test__colorize test_copy test_ctypes test_enum test_genericalias test_patma test_pprint test_pydoc test_regrtest test_zoneinfo
      • inspect: test_abc test_argparse test_asyncgen test_buffer test_code test_collections test_coroutines test_decimal test_generators test_grammar test_monitoring test_ntpath test_operator test_posixpath test_signal test_sqlite3 test_traceback test_types test_unittest test_yield_from test_zipimport
    • dbm.dumb: test_dbm_dumb
    • inspect:
      • bdb: test_bdb
      • cmd: test_cmd
      • importlib.metadata: test_importlib
      • pkgutil: test_pkgutil test_runpy
      • rlcompleter: test_rlcompleter
      • trace: test_trace
      • xmlrpc.server: test_docxmlrpc test_xmlrpc
    • pyclbr: test_pyclbr
    • traceback: test_asyncio test_code_module test_contextlib test_contextlib_async test_dictcomps test_exceptions test_http_cookiejar test_importlib test_iter test_listcomps test_pyexpat test_setcomps test_socket test_subprocess test_sys test_threadedtempfile test_threading test_unittest test_with
      • concurrent.futures.process: test_compileall test_concurrent_futures
      • http.cookiejar: test_urllib2
      • logging: test_asyncio test_hashlib test_logging test_support test_urllib2net
      • multiprocessing: test_asyncio test_concurrent_futures test_fcntl test_memoryview test_multiprocessing_main_handling test_re
      • py_compile: test_cmd_line_script test_importlib test_modulefinder test_py_compile
      • socketserver: test_imaplib test_socketserver test_wsgiref
      • threading: test_android test_asyncio test_bz2 test_concurrent_futures test_ctypes test_email test_fork1 test_frame test_ftplib test_gc test_httplib test_httpservers test_importlib test_io test_itertools test_largefile test_linecache test_opcache test_pathlib test_poll test_poplib test_queue test_robotparser test_sched test_smtplib test_super test_syslog test_termios test_threading_local test_time test_urllib2_localnet test_weakref test_winreg test_zstd
      • timeit: test_timeit

Legend:

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

youknowone
youknowone approved these changes Apr 24, 2026
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👍

@youknowone
youknowone merged commit 0913563 into RustPython:main Apr 24, 2026
21 checks passed
@changjoon-park
changjoon-park deleted the fix-stmt-none-disallowed branch April 27, 2026 13:24
youknowone pushed a commit that referenced this pull request Sep 16, 2026
@changjoon-park
Raise ValueError for None in Stmt lists to match CPython validator (#…
a66323d 
…7670)

Sibling fix to #7656 (which handled Vec<Expr>). The same catch-all
TypeError ("expected some sort of stmt, but got {}") in
Stmt::ast_from_object silently swallowed None, so compile() on an
AST with None in a statement-list field (ClassDef.body, Try.body,
For.body, etc.) raised TypeError where CPython raises
ValueError("None disallowed in statement list").

Add an is_none check before the catch-all, matching the Expr-side
shape introduced in #7656. Option<Stmt> positions are unaffected —
they short-circuit None earlier in node.rs.

Unmasks test_classdef (body=[None] sub-case). Full
test.test_ast.test_ast run: 227 tests, 0 unexpected successes, 38
expected failures (was 39).
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