Inline __slots__ invalidation logic into PyClass (PY-29268)

python/psi-api/src/com/jetbrains/python/psi/PyClass.java

@@ -266,7 +266,13 @@ public interface PyClass extends PsiNameIdentifierOwner, PyStatement, PyDocStrin
   boolean isSubclass(@NotNull String superClassQName, @Nullable TypeEvalContext context);
 
   /**
-   * Returns the aggregated list of names defined in __slots__ attributes of the class and its ancestors.
+   * Returns the aggregated list of names defined in `__slots__` attributes of the class and its ancestors.
+   * <p>
+   * Returned value is `null` if class or at least one of its ancestor does not follow the next conditions:
+   * <ul>
+   * <li>it should be a new style class</li>
+   * <li>its `__slots__` should exist and should not contain `__dict__`</li>
+   * </ul>
    *
    * @param context (will be used default if null)
    */

python/src/com/jetbrains/python/inspections/PyDunderSlotsInspection.kt

@@ -101,7 +101,7 @@ class PyDunderSlotsInspection : PyInspection() {
     }
 
     private fun attributeIsWritableInPy2(cls: PyClass, name: String): Boolean {
-      val slots = PyUtil.deactivateSlots(cls, cls.getSlots(myTypeEvalContext), myTypeEvalContext)
+      val slots = cls.getSlots(myTypeEvalContext)
       return slots == null ||
              slots.contains(name) && cls.findClassAttribute(name, true, myTypeEvalContext) == null ||
              cls.findProperty(name, true, myTypeEvalContext) != null

python/src/com/jetbrains/python/psi/impl/PyClassImpl.java

@@ -1,6 +1,7 @@
 // Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.jetbrains.python.psi.impl;
 
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.intellij.codeInsight.completion.CompletionUtil;
 import com.intellij.lang.ASTNode;
@@ -259,24 +260,27 @@ public class PyClassImpl extends PyBaseElementImpl<PyClassStub> implements PyCla
   @Override
   @Nullable
   public List<String> getSlots(@Nullable TypeEvalContext context) {
-    final List<String> ownSlots = getOwnSlots();
-    if (ownSlots == null) {
-      return null;
-    }
+    final Set<String> result = new LinkedHashSet<>();
 
-    final Set<String> result = new LinkedHashSet<>(ownSlots);
+    final PyClassType currentType = new PyClassTypeImpl(this, true);
+    final TypeEvalContext contextToUse = context != null ? context : TypeEvalContext.codeInsightFallback(getProject());
 
-    for (PyClass cls : getAncestorClasses(context)) {
+    for (PyClassLikeType type : Iterables.concat(Collections.singletonList(currentType), getAncestorTypes(contextToUse))) {
+      if (!(type instanceof PyClassType)) return null;
+
+      final PyClass cls = ((PyClassType)type).getPyClass();
       if (PyUtil.isObjectClass(cls)) {
         continue;
       }
 
-      final List<String> ancestorSlots = cls.getOwnSlots();
-      if (ancestorSlots == null) {
+      if (!cls.isNewStyleClass(contextToUse)) return null;
+
+      final List<String> ownSlots = cls.getOwnSlots();
+      if (ownSlots == null || ownSlots.contains(PyNames.DICT)) {
         return null;
       }
 
-      result.addAll(ancestorSlots);
+      result.addAll(ownSlots);
     }
 
     return new ArrayList<>(result);

python/src/com/jetbrains/python/psi/types/PyClassTypeImpl.java

@@ -747,7 +747,7 @@ public class PyClassTypeImpl extends UserDataHolderBase implements PyClassType {
     final TypeEvalContext context =
       (expressionHook != null ? TypeEvalContext.codeCompletion(myClass.getProject(), myClass.getContainingFile()) : null);
 
-    processor.setAllowedNames(PyUtil.deactivateSlots(myClass, myClass.getSlots(context), context));
+    processor.setAllowedNames(myClass.getSlots(context));
     myClass.processInstanceLevelDeclarations(processor, expressionHook);
 
     for (LookupElement le : processor.getResultList()) {

python/testData/stubs/Slots.py

@@ -1,2 +1,2 @@
-class A:
+class A(object):
     __slots__ = ['foo', 'bar']

python/testSrc/com/jetbrains/python/inspections/PyDunderSlotsInspectionTest.java

@@ -269,6 +269,25 @@ public class PyDunderSlotsInspectionTest extends PyInspectionTestCase {
     );
   }
 
+  // PY-29268
+  public void testWriteToNewStyleInheritedFromOldStyle() {
+    doTestByText("class A:\n" +
+                 "    __slots__ = ['a']\n" +
+                 "\n" +
+                 "class B(A, object):\n" +
+                 "    __slots__ = ['b']\n" +
+                 "\n" +
+                 "B().c = 1");
+  }
+
+  // PY-29268
+  public void testWriteToNewStyleInheritedFromUnknown() {
+    doTestByText("class B(A, object):\n" +
+                 "    __slots__ = ['b']\n" +
+                 "\n" +
+                 "B().c = 1");
+  }
+
   private void doTestPy2() {
     runWithLanguageLevel(LanguageLevel.PYTHON26, this::doTest);
   }