[pyflakes] Ignore errors in @no_type_check string annotations (`F…

…722`, `F821`) (#15215)

crates/ruff_linter/resources/test/fixtures/pyflakes/F401_32.py

@@ -0,0 +1,8 @@
+from datetime import datetime
+from typing import no_type_check
+
+
+# No errors
+
+@no_type_check
+def f(a: datetime, b: "datetime"): ...

crates/ruff_linter/resources/test/fixtures/pyflakes/F722_1.py

@@ -0,0 +1,16 @@
+from typing import no_type_check
+
+
+# Errors
+
+@no_type_check
+class C:
+    def f(self, arg: "this isn't python") -> "this isn't python either":
+        x: "this also isn't python" = 1
+
+
+# No errors
+
+@no_type_check
+def f(arg: "this isn't python") -> "this isn't python either":
+    x: "this also isn't python" = 0

crates/ruff_linter/resources/test/fixtures/pyflakes/F821_31.py

@@ -0,0 +1,16 @@
+import typing
+
+
+# Errors
+
+@typing.no_type_check
+class C:
+    def f(self, arg: "B") -> "S":
+        x: "B" = 1
+
+
+# No errors
+
+@typing.no_type_check
+def f(arg: "A") -> "R":
+    x: "A" = 1

crates/ruff_linter/src/checkers/ast/analyze/unresolved_references.rs

@@ -24,6 +24,10 @@ pub(crate) fn unresolved_references(checker: &mut Checker) {
             }
         } else {
             if checker.enabled(Rule::UndefinedName) {
+                if checker.semantic.in_no_type_check() {
+                    continue;
+                }
+
                 // Avoid flagging if `NameError` is handled.
                 if reference.exceptions().contains(Exceptions::NAME_ERROR) {
                     continue;

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -449,6 +449,13 @@ impl<'a> Checker<'a> {
             match_fn(expr)
         }
     }
+
+    /// Push `diagnostic` if the checker is not in a `@no_type_check` context.
+    pub(crate) fn push_type_diagnostic(&mut self, diagnostic: Diagnostic) {
+        if !self.semantic.in_no_type_check() {
+            self.diagnostics.push(diagnostic);
+        }
+    }
 }
 
 impl<'a> Visitor<'a> for Checker<'a> {
@@ -724,6 +731,13 @@ impl<'a> Visitor<'a> for Checker<'a> {
                 // deferred.
                 for decorator in decorator_list {
                     self.visit_decorator(decorator);
+
+                    if self
+                        .semantic
+                        .match_typing_expr(&decorator.expression, "no_type_check")
+                    {
+                        self.semantic.flags |= SemanticModelFlags::NO_TYPE_CHECK;
+                    }
                 }
 
                 // Function annotations are always evaluated at runtime, unless future annotations
@@ -2348,8 +2362,10 @@ impl<'a> Checker<'a> {
                     }
                     self.parsed_type_annotation = None;
                 } else {
+                    self.semantic.restore(snapshot);
+
                     if self.enabled(Rule::ForwardAnnotationSyntaxError) {
-                        self.diagnostics.push(Diagnostic::new(
+                        self.push_type_diagnostic(Diagnostic::new(
                             pyflakes::rules::ForwardAnnotationSyntaxError {
                                 body: string_expr.value.to_string(),
                             },

crates/ruff_linter/src/rules/pyflakes/mod.rs

@@ -55,6 +55,7 @@ mod tests {
     #[test_case(Rule::UnusedImport, Path::new("F401_21.py"))]
     #[test_case(Rule::UnusedImport, Path::new("F401_22.py"))]
     #[test_case(Rule::UnusedImport, Path::new("F401_23.py"))]
+    #[test_case(Rule::UnusedImport, Path::new("F401_32.py"))]
     #[test_case(Rule::ImportShadowedByLoopVar, Path::new("F402.py"))]
     #[test_case(Rule::ImportShadowedByLoopVar, Path::new("F402.ipynb"))]
     #[test_case(Rule::UndefinedLocalWithImportStar, Path::new("F403.py"))]
@@ -95,6 +96,7 @@ mod tests {
     #[test_case(Rule::ReturnOutsideFunction, Path::new("F706.py"))]
     #[test_case(Rule::DefaultExceptNotLast, Path::new("F707.py"))]
     #[test_case(Rule::ForwardAnnotationSyntaxError, Path::new("F722.py"))]
+    #[test_case(Rule::ForwardAnnotationSyntaxError, Path::new("F722_1.py"))]
     #[test_case(Rule::RedefinedWhileUnused, Path::new("F811_0.py"))]
     #[test_case(Rule::RedefinedWhileUnused, Path::new("F811_1.py"))]
     #[test_case(Rule::RedefinedWhileUnused, Path::new("F811_2.py"))]
@@ -160,6 +162,7 @@ mod tests {
     #[test_case(Rule::UndefinedName, Path::new("F821_27.py"))]
     #[test_case(Rule::UndefinedName, Path::new("F821_28.py"))]
     #[test_case(Rule::UndefinedName, Path::new("F821_30.py"))]
+    #[test_case(Rule::UndefinedName, Path::new("F821_31.py"))]
     #[test_case(Rule::UndefinedExport, Path::new("F822_0.py"))]
     #[test_case(Rule::UndefinedExport, Path::new("F822_0.pyi"))]
     #[test_case(Rule::UndefinedExport, Path::new("F822_1.py"))]

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F401_F401_32.py.snap

@@ -0,0 +1,5 @@
+---
+source: crates/ruff_linter/src/rules/pyflakes/mod.rs
+snapshot_kind: text
+---
+

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F722_F722_1.py.snap

@@ -0,0 +1,29 @@
+---
+source: crates/ruff_linter/src/rules/pyflakes/mod.rs
+snapshot_kind: text
+---
+F722_1.py:8:22: F722 Syntax error in forward annotation: `this isn't python`
+  |
+6 | @no_type_check
+7 | class C:
+8 |     def f(self, arg: "this isn't python") -> "this isn't python either":
+  |                      ^^^^^^^^^^^^^^^^^^^ F722
+9 |         x: "this also isn't python" = 1
+  |
+
+F722_1.py:8:46: F722 Syntax error in forward annotation: `this isn't python either`
+  |
+6 | @no_type_check
+7 | class C:
+8 |     def f(self, arg: "this isn't python") -> "this isn't python either":
+  |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ F722
+9 |         x: "this also isn't python" = 1
+  |
+
+F722_1.py:9:12: F722 Syntax error in forward annotation: `this also isn't python`
+  |
+7 | class C:
+8 |     def f(self, arg: "this isn't python") -> "this isn't python either":
+9 |         x: "this also isn't python" = 1
+  |            ^^^^^^^^^^^^^^^^^^^^^^^^ F722
+  |

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F821_F821_31.py.snap

@@ -0,0 +1,53 @@
+---
+source: crates/ruff_linter/src/rules/pyflakes/mod.rs
+snapshot_kind: text
+---
+F821_31.py:8:23: F821 Undefined name `B`
+  |
+6 | @typing.no_type_check
+7 | class C:
+8 |     def f(self, arg: "B") -> "S":
+  |                       ^ F821
+9 |         x: "B" = 1
+  |
+
+F821_31.py:8:31: F821 Undefined name `S`
+  |
+6 | @typing.no_type_check
+7 | class C:
+8 |     def f(self, arg: "B") -> "S":
+  |                               ^ F821
+9 |         x: "B" = 1
+  |
+
+F821_31.py:9:13: F821 Undefined name `B`
+  |
+7 | class C:
+8 |     def f(self, arg: "B") -> "S":
+9 |         x: "B" = 1
+  |             ^ F821
+  |
+
+F821_31.py:15:13: F821 Undefined name `A`
+   |
+14 | @typing.no_type_check
+15 | def f(arg: "A") -> "R":
+   |             ^ F821
+16 |     x: "A" = 1
+   |
+
+F821_31.py:15:21: F821 Undefined name `R`
+   |
+14 | @typing.no_type_check
+15 | def f(arg: "A") -> "R":
+   |                     ^ F821
+16 |     x: "A" = 1
+   |
+
+F821_31.py:16:9: F821 Undefined name `A`
+   |
+14 | @typing.no_type_check
+15 | def f(arg: "A") -> "R":
+16 |     x: "A" = 1
+   |         ^ F821
+   |

crates/ruff_python_semantic/src/model.rs

@@ -1935,6 +1935,11 @@ impl<'a> SemanticModel<'a> {
             .intersects(SemanticModelFlags::ATTRIBUTE_DOCSTRING)
     }
 
+    /// Return `true` if the model is in a `@no_type_check` context.
+    pub const fn in_no_type_check(&self) -> bool {
+        self.flags.intersects(SemanticModelFlags::NO_TYPE_CHECK)
+    }
+
     /// Return `true` if the model has traversed past the "top-of-file" import boundary.
     pub const fn seen_import_boundary(&self) -> bool {
         self.flags.intersects(SemanticModelFlags::IMPORT_BOUNDARY)
@@ -2477,6 +2482,23 @@ bitflags! {
         /// ```
         const ASSERT_STATEMENT = 1 << 29;
 
+        /// The model is in a [`@no_type_check`] context.
+        ///
+        /// This is used to skip type checking when the `@no_type_check` decorator is found.
+        ///
+        /// For example (adapted from [#13824]):
+        /// ```python
+        /// from typing import no_type_check
+        ///
+        /// @no_type_check
+        /// def fn(arg: "A") -> "R":
+        ///     pass
+        /// ```
+        ///
+        /// [no_type_check]: https://docs.python.org/3/library/typing.html#typing.no_type_check
+        /// [#13824]: https://github.com/astral-sh/ruff/issues/13824
+        const NO_TYPE_CHECK = 1 << 30;
+
         /// The context is in any type annotation.
         const ANNOTATION = Self::TYPING_ONLY_ANNOTATION.bits() | Self::RUNTIME_EVALUATED_ANNOTATION.bits() | Self::RUNTIME_REQUIRED_ANNOTATION.bits();