[red-knot] Reachability analysis by sharkdp · Pull Request #17199 · astral-sh/ruff

sharkdp · 2025-04-04T11:11:53Z

Summary

This PR proposes a new approach to silencing unresolved-reference diagnostics by keeping track of the reachability of each use of a symbol. The changes merged in #17169 are still needed for the "Use of variable in nested function" test case, but that could also be solved in another way eventually (see astral-sh/ty#210). We can use the same technique to silence unresolved-import and unresolved-attribute false-positives, but I think this could be merged in isolation.

Test Plan

New Markdown tests, ecosystem tests

github-actions · 2025-04-04T11:13:45Z

`mypy_primer` results

Changes were detected when running on open source projects

packaging (https://github.com/pypa/packaging)
- warning[lint:unresolved-reference] /tmp/mypy_primer/projects/packaging/src/packaging/metadata.py:28:22: Name `ExceptionGroup` used when not defined
- Found 96 diagnostics
+ Found 95 diagnostics

werkzeug (https://github.com/pallets/werkzeug)
- warning[lint:possibly-unresolved-reference] /tmp/mypy_primer/projects/werkzeug/src/werkzeug/formparser.py:64:36: Name `TemporaryFile` used when possibly not defined
- Found 683 diagnostics
+ Found 682 diagnostics

rich (https://github.com/Textualize/rich)
- warning[lint:unresolved-reference] /tmp/mypy_primer/projects/rich/rich/traceback.py:462:43: Name `BaseExceptionGroup` used when not defined
- warning[lint:unresolved-reference] /tmp/mypy_primer/projects/rich/rich/traceback.py:462:63: Name `ExceptionGroup` used when not defined
- warning[lint:unresolved-reference] /tmp/mypy_primer/projects/rich/tests/test_progress.py:186:13: Name `_time` used when not defined
- warning[lint:unresolved-reference] /tmp/mypy_primer/projects/rich/tests/test_progress.py:499:20: Name `time` used when not defined
- Found 382 diagnostics
+ Found 378 diagnostics

sharkdp · 2025-04-04T18:39:01Z

crates/red_knot_python_semantic/src/semantic_index/use_def.rs

+    /// use(y)
+    /// ```
+    /// Depending on the value of `test`, the `y = 1`, `y = 2`, or both bindings may be visible.
+    /// The use of `x` is recorded with a reachability constraint of `[test]`.


I'm completely fine with keeping this more concise.

sharkdp · 2025-04-04T18:39:35Z

crates/red_knot_python_semantic/resources/mdtest/unreachable.md

+### Attributes
+
+When attribute expressions appear in unreachable code, we should not emit `unresolved-attribute`
+diagnostics:
+
+```py
+import sys
+import builtins
+
+if sys.version_info >= (3, 11):
+    # TODO
+    # error: [unresolved-attribute]
+    builtins.ExceptionGroup
+```
+
+### Imports
+
+When import statements appear in unreachable code, we should not emit `unresolved-import`
+diagnostics:
+
+```py
+import sys
+
+if sys.version_info >= (3, 11):
+    # TODO
+    # error: [unresolved-import]
+    from builtins import ExceptionGroup
+
+    # TODO
+    # error: [unresolved-import]
+    import builtins.ExceptionGroup
+
+    # See https://docs.python.org/3/whatsnew/3.11.html#new-modules
+
+    # TODO
+    # error: [unresolved-import]
+    import tomllib
+
+    # TODO
+    # error: [unresolved-import]
+    import wsgiref.types
+```


I will leave attributes and imports for a follow up. I want to get some feedback on this first.

sharkdp · 2025-04-04T19:29:35Z

crates/red_knot_python_semantic/resources/mdtest/unreachable.md


 In the example below, since we use `x` in the `inner` function, we use the "public" type of `x`,
 which currently refers to the end-of-scope type of `x`. Since the end of the `outer` scope is
-unreachable, we treat `x` as if it was not defined. This behavior can certainly be improved.


Nothing changed in this test, but this explanation was outdated. And the return x # … below as confusing.

sharkdp · 2025-04-04T19:30:13Z

crates/red_knot_python_semantic/resources/mdtest/unreachable.md


    def inner():
-        return x  # Name `x` used when not defined
+        reveal_type(x)  # revealed: Unknown


The fact that we reveal Unknown here is tracked in https://github.com/astral-sh/ruff/issues/15777

sharkdp · 2025-04-04T19:31:16Z

crates/red_knot_python_semantic/resources/mdtest/unreachable.md

-FEATURE_X_ACTIVATED = False
+from typing import Literal
+
+FEATURE_X_ACTIVATED: Literal[False] = False


We don't support Final yet, so I needed to declare this as Literal[False]. Otherwise, the public type (which we use below) would be Unknown | Literal[False].

crates/red_knot_python_semantic/src/types/infer.rs

carljm

Looks good to me!

crates/red_knot_python_semantic/src/semantic_index/use_def.rs

* origin/main: [red-knot] Default `python-platform` to current platform (#17183) [red-knot] Add new 'unreachable code' test case (#17306) [red-knot] mypy_primer: Run on `async-utils` (#17303) [red-knot] Add custom `__setattr__` support (#16748) [red-knot] Add `__init__` arguments check when doing `try_call` on a class literal (#16512) [`flake8-pie`] Avoid false positive for multiple assignment with `auto()` (`PIE796`) (#17274) [syntax-errors] Async comprehension in sync comprehension (#17177) [`airflow`] Expand module path check to individual symbols (`AIR302`) (#17278) [syntax-errors] Check annotations in annotated assignments (#17283) [syntax-errors] Extend annotation checks to `await` (#17282) [red-knot] Add support for `assert_never` (#17287) [`flake8-pytest-style`] Avoid false positive for legacy form of `pytest.raises` (`PT011`) (#17231) [red-knot] Do not show types for literal expressions on hover (#17290) [red-knot] Fix dead-code clippy warning (#17291) [red-knot] Reachability analysis (#17199) [red-knot] Don't use latency-sensitive for handlers (#17227)

sharkdp added the ty Multi-file analysis & type inference label Apr 4, 2025

sharkdp force-pushed the david/silence-unresolved-reference-in-unreachable-code-pt2 branch 3 times, most recently from 751b05e to 05a808b Compare April 4, 2025 18:37

sharkdp commented Apr 4, 2025

View reviewed changes

sharkdp force-pushed the david/silence-unresolved-reference-in-unreachable-code-pt2 branch from 05a808b to 7ae5d31 Compare April 4, 2025 18:43

sharkdp marked this pull request as ready for review April 4, 2025 18:47

sharkdp requested review from AlexWaygood, carljm and dcreager as code owners April 4, 2025 18:47

sharkdp force-pushed the david/silence-unresolved-reference-in-unreachable-code-pt2 branch from 7ae5d31 to 100d88b Compare April 4, 2025 19:29

sharkdp commented Apr 4, 2025

View reviewed changes

crates/red_knot_python_semantic/src/types/infer.rs Show resolved Hide resolved

carljm approved these changes Apr 8, 2025

View reviewed changes

crates/red_knot_python_semantic/src/semantic_index/use_def.rs Show resolved Hide resolved

sharkdp added 2 commits April 8, 2025 08:21

[red-knot] Reachability analysis

c1d5778

shrink_to_fit

03a2dcf

sharkdp force-pushed the david/silence-unresolved-reference-in-unreachable-code-pt2 branch from 100d88b to 03a2dcf Compare April 8, 2025 06:21

sharkdp merged commit 60f2e67 into main Apr 8, 2025
23 checks passed

sharkdp deleted the david/silence-unresolved-reference-in-unreachable-code-pt2 branch April 8, 2025 06:37

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[red-knot] Reachability analysis#17199

[red-knot] Reachability analysis#17199
sharkdp merged 2 commits intomainfrom
david/silence-unresolved-reference-in-unreachable-code-pt2

sharkdp commented Apr 4, 2025 •

edited

Loading

Uh oh!

github-actions bot commented Apr 4, 2025 •

edited

Loading

Uh oh!

sharkdp Apr 4, 2025

Uh oh!

sharkdp Apr 4, 2025

Uh oh!

sharkdp Apr 4, 2025

Uh oh!

sharkdp Apr 4, 2025

Uh oh!

sharkdp Apr 4, 2025

Uh oh!

Uh oh!

carljm left a comment

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

sharkdp commented Apr 4, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Test Plan

Uh oh!

github-actions bot commented Apr 4, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

mypy_primer results

Uh oh!

sharkdp Apr 4, 2025

Choose a reason for hiding this comment

Uh oh!

sharkdp Apr 4, 2025

Choose a reason for hiding this comment

Uh oh!

sharkdp Apr 4, 2025

Choose a reason for hiding this comment

Uh oh!

sharkdp Apr 4, 2025

Choose a reason for hiding this comment

Uh oh!

sharkdp Apr 4, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

carljm left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

sharkdp commented Apr 4, 2025 •

edited

Loading

github-actions bot commented Apr 4, 2025 •

edited

Loading

`mypy_primer` results