Provide detailed error for circular `from` imports#5972

ever0de

Summary by CodeRabbit

Bug Fixes
- Improved error messages when importing names from a module, providing clearer information in cases of circular imports or partial initialization.
New Features
- Enhanced detection of modules that are still initializing, helping users identify circular import issues more easily.

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📥 Commits

Reviewing files that changed from the base of the PR and between 9d6912c and 69c0294.

📒 Files selected for processing (1)

vm/src/frame.rs (2 hunks)

Walkthrough

The import_from method in the ExecutingFrame struct was revised to improve error handling and fallback logic during module imports. A new helper function, is_module_initializing, was introduced to check if a module is still initializing, allowing for more precise import error messages, especially in cases of circular imports or partial initialization.

Changes

File(s)	Change Summary
vm/src/frame.rs	Refactored `import_from` to improve fallback logic and error reporting; added `is_module_initializing` helper function.

Poem

In the warren of code, a module peeks through,
Importing its friends, as rabbits often do.
If caught in a loop, or half-awake yawn,
A new error message hops helpfully on.
With clearer advice, imports now sing—
No more confusion in the Python spring! 🐇

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Actionable comments posted: 2

📜 Review details

Configuration used: .coderabbit.yml
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📥 Commits

Reviewing files that changed from the base of the PR and between fd35c7a and d86644e.

⛔ Files ignored due to path filters (1)

Lib/test/test_import/__init__.py is excluded by !Lib/**

📒 Files selected for processing (3)

vm/src/builtins/module.rs (3 hunks)
vm/src/frame.rs (2 hunks)
vm/src/import.rs (2 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.rs

Instructions used from:

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.github/copilot-instructions.md

🧠 Learnings (2)

vm/src/builtins/module.rs (1)

Learnt from: CR
PR: RustPython/RustPython#0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-06-30T10:08:48.858Z
Learning: Applies to **/*.rs : Use the macro system (`pyclass`, `pymodule`, `pyfunction`, etc.) when implementing Python functionality in Rust

vm/src/import.rs (1)

Learnt from: CR
PR: RustPython/RustPython#0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-06-30T10:08:48.858Z
Learning: Applies to **/*.rs : Use the macro system (`pyclass`, `pymodule`, `pyfunction`, etc.) when implementing Python functionality in Rust

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

GitHub Check: Run snippets and cpython tests (windows-latest)

🔇 Additional comments (4)

vm/src/builtins/module.rs (2)

1-1: LGTM! Atomic boolean field properly added for initialization tracking.

The AtomicBool import and field addition are appropriate for tracking module initialization state in a thread-safe manner.

Also applies to: 57-57

80-80: Field initialization is correct in both constructors.

The initializing field is properly initialized to false in both new() and from_def() constructors, ensuring modules start in a non-initializing state.

Also applies to: 88-88

vm/src/import.rs (2)

3-3: Imports correctly added for atomic operations.

The Ordering import and PyModule addition are necessary for the initialization tracking implementation.

Also applies to: 7-7

161-178: Well-implemented guard pattern for initialization tracking.

The guard ensures the initializing flag is always reset, even if module code execution fails or panics. The use of Ordering::Relaxed is appropriate here.

However, this sets an internal field that isn't exposed to Python code. The frame.rs code checks __spec__._initializing, which is a different attribute. Consider exposing this state to Python.

ever0de

ref

https://github.com/python/cpython/blob/a68ddea3bf7e9bb77d096c613bce2ec1e67a28f4/Lib/importlib/_bootstrap.py#L914-L955

youknowone

nice feature! Thanks!

ever0de force-pushed the fix/circular-import-error branch 2 times, most recently from 9c09aef to dfb4db1 Compare July 14, 2025 15:04

fix(vm): provide detailed error for circular from imports

d86644e

ever0de force-pushed the fix/circular-import-error branch from dfb4db1 to d86644e Compare July 14, 2025 15:07

ever0de changed the title ~~fix(vm): provide detailed error for circular from imports~~ Jul 14, 2025

ever0de marked this pull request as ready for review July 14, 2025 15:22

coderabbitai Bot reviewed Jul 14, 2025

View reviewed changes

ever0de added 2 commits July 15, 2025 00:47

refactor?

e4dc90f

remove native flag

9d6912c

ever0de added 2 commits July 15, 2025 01:05

use identifier & rollback comment

e53917c

remove unneeded as_str

69c0294

ever0de force-pushed the fix/circular-import-error branch from 2d99040 to 69c0294 Compare July 14, 2025 16:09

youknowone approved these changes Jul 14, 2025

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coderabbitai Bot mentioned this pull request Feb 8, 2026

Fix test_import: import machinery, circular imports, and script shadowing #7034

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Provide detailed error for circular `from` imports#5972