[PY-73290] Fix missing deprecation warnings for property setters

python/python-psi-impl/src/com/jetbrains/python/inspections/PyDeprecationInspection.java

@@ -23,18 +23,26 @@
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiElementVisitor;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.jetbrains.python.psi.AccessDirection;
+import com.jetbrains.python.psi.Property;
 import com.jetbrains.python.psi.PyBinaryExpression;
+import com.jetbrains.python.psi.PyCallable;
+import com.jetbrains.python.psi.PyClass;
 import com.jetbrains.python.psi.PyDeprecatable;
 import com.jetbrains.python.psi.PyElement;
 import com.jetbrains.python.psi.PyExceptPart;
 import com.jetbrains.python.psi.PyExpression;
 import com.jetbrains.python.psi.PyFile;
 import com.jetbrains.python.psi.PyFromImportStatement;
 import com.jetbrains.python.psi.PyReferenceExpression;
+import com.jetbrains.python.psi.PyTargetExpression;
 import com.jetbrains.python.psi.PyUtil;
+import com.jetbrains.python.psi.types.PyClassType;
+import com.jetbrains.python.psi.types.PyType;
 import com.jetbrains.python.psi.types.TypeEvalContext;
 import com.jetbrains.python.pyi.PyiFile;
 import com.jetbrains.python.pyi.PyiUtil;
+import com.jetbrains.python.toolbox.Maybe;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -98,6 +106,48 @@ else if (resolveResult instanceof PyFile) {
       }
     }
 
+    @Override
+    public void visitPyTargetExpression(@NotNull PyTargetExpression node) {
+      final PyExpression qualifier = node.getQualifier();
+      if (qualifier == null) return;
+
+      final String name = node.getName();
+      if (name == null) return;
+
+      final PyType type = myTypeEvalContext.getType(qualifier);
+      if (!(type instanceof PyClassType classType)) return;
+
+      final PyClass cls = classType.getPyClass();
+      final Property property = cls.findProperty(name, true, myTypeEvalContext);
+      if (property == null) return;
+
+      final Maybe<PyCallable> accessor = property.getByDirection(AccessDirection.WRITE);
+      if (!accessor.isDefined() || accessor.value() == null) return;
+
+      final PyCallable callable = accessor.value();
+      if (!(callable instanceof PyDeprecatable deprecatable)) return;
+
+      @NlsSafe String deprecationMessage = deprecatable.getDeprecationMessage();
+
+      if (deprecationMessage == null && !(callable.getContainingFile() instanceof PyiFile)) {
+        PsiElement classStub = PyiUtil.getPythonStub(cls);
+        if (classStub instanceof PyClass stubClass) {
+          Property stubProperty = stubClass.findProperty(name, true, myTypeEvalContext);
+          if (stubProperty != null) {
+            PyCallable stubSetter = stubProperty.getByDirection(AccessDirection.WRITE).valueOrNull();
+            if (stubSetter instanceof PyDeprecatable stubDeprecatable) {
+              deprecationMessage = stubDeprecatable.getDeprecationMessage();
+            }
+          }
+        }
+      }
+
+      if (deprecationMessage != null) {
+        PsiElement nameIdentifier = node.getNameIdentifier();
+        registerProblem(nameIdentifier == null ? node : nameIdentifier, deprecationMessage, ProblemHighlightType.LIKE_DEPRECATED);
+      }
+    }
+
     private @Nullable PyElement resolve(@NotNull PyReferenceExpression node) {
       final PyElement resolve = PyUtil.as(node.getReference(getResolveContext()).resolve(), PyElement.class);
       return resolve == null ? null : PyiUtil.getOriginalElementOrLeaveAsIs(resolve, PyElement.class);

python/testData/deprecation/deprecatedPropertySetter.py

@@ -0,0 +1,18 @@
+#  Copyright 2000-2026 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+
+class Foo:
+    def __init__(self):
+        self._value = None
+
+    @property
+    def value(self):
+        return self._value
+
+    @value.setter
+    def value(self, new_value):
+        import warnings
+        warnings.warn("this setter is deprecated", DeprecationWarning, 2)
+        self._value = new_value
+
+foo = Foo()
+foo.<warning descr="this setter is deprecated">value</warning> = 1

python/testData/deprecation/deprecatedPropertySetterFromStub.py

@@ -0,0 +1,16 @@
+#  Copyright 2000-2026 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+
+class Foo:
+    def __init__(self):
+        self._value = None
+
+    @property
+    def value(self):
+        return self._value
+
+    @value.setter
+    def value(self, new_value):
+        self._value = new_value
+
+foo = Foo()
+foo.<warning descr="this setter is deprecated in stub">value</warning> = 1

python/testData/deprecation/deprecatedPropertySetterFromStub.pyi

@@ -0,0 +1,10 @@
+#  Copyright 2000-2026 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+
+class Foo:
+    @property
+    def value(self): ...
+
+    @value.setter
+    def value(self, new_value):
+        import warnings
+        warnings.warn("this setter is deprecated in stub", DeprecationWarning, 2)

python/testSrc/com/jetbrains/python/PyDeprecationTest.java

@@ -57,6 +57,18 @@ public void testDeprecatedProperty() {
     myFixture.checkHighlighting(true, false, false);
   }
 
+  public void testDeprecatedPropertySetter() {
+    myFixture.enableInspections(PyDeprecationInspection.class);
+    myFixture.configureByFile("deprecation/deprecatedPropertySetter.py");
+    myFixture.checkHighlighting(true, false, false);
+  }
+
+  public void testDeprecatedPropertySetterFromStub() {
+    myFixture.enableInspections(PyDeprecationInspection.class);
+    myFixture.configureByFiles("deprecation/deprecatedPropertySetterFromStub.py", "deprecation/deprecatedPropertySetterFromStub.pyi");
+    myFixture.checkHighlighting(true, false, false);
+  }
+
   public void testDeprecatedImport() {
     myFixture.enableInspections(PyDeprecationInspection.class);
     myFixture.configureByFiles("deprecation/deprecatedImport.py", "deprecation/deprecatedModule.py");