From 3cb186667eca7b6507e0bf08eedcf7223816308b Mon Sep 17 00:00:00 2001
From: Semyon Proshev <Semyon.Proshev@jetbrains.com>
Date: Fri, 31 May 2019 16:16:18 +0300
Subject: [PATCH] Raise a warning on inherited `Final`s reassignment on class
 level (PEP 591) (PY-34945)

GitOrigin-RevId: 8d06617819ab21c83a053a0c36da5495b503288b
---
 .../python/inspections/PyFinalInspection.kt   | 21 +++++++++++++++++++
 .../ImportedClassFinalReassignment/a.py       |  5 ++++-
 .../inspections/PyFinalInspectionTest.java    |  6 ++++--
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/python/src/com/jetbrains/python/inspections/PyFinalInspection.kt b/python/src/com/jetbrains/python/inspections/PyFinalInspection.kt
index 0d92b56764e3..7a3eeeeb3d36 100644
--- a/python/src/com/jetbrains/python/inspections/PyFinalInspection.kt
+++ b/python/src/com/jetbrains/python/inspections/PyFinalInspection.kt
@@ -111,6 +111,14 @@ class PyFinalInspection : PyInspection() {
         else if (PyUtil.multiResolveTopPriority(node, resolveContext).any { it != node && it is PyTargetExpression && isFinal(it) }) {
           registerProblem(node, "'${node.name}' is 'Final' and could not be reassigned")
         }
+        else {
+          if (!node.isQualified) {
+            val scopeOwner = ScopeUtil.getScopeOwner(node)
+            if (scopeOwner is PyClass) {
+              checkInheritedClassFinalReassignmentOnClassLevel(node, scopeOwner)
+            }
+          }
+        }
       }
 
       if (isFinal(node) && PyUtil.multiResolveTopPriority(node, resolveContext).any { it != node }) {
@@ -265,6 +273,19 @@ class PyFinalInspection : PyInspection() {
       }
     }
 
+    private fun checkInheritedClassFinalReassignmentOnClassLevel(target: PyTargetExpression, cls: PyClass) {
+      val name = target.name ?: return
+
+      for (ancestor in cls.getAncestorClasses(myTypeEvalContext)) {
+        val ancestorClassAttribute = ancestor.findClassAttribute(name, false, myTypeEvalContext)
+
+        if (ancestorClassAttribute != null && ancestorClassAttribute.hasAssignedValue() && isFinal(ancestorClassAttribute)) {
+          registerProblem(target, "'${ancestor.name}.$name' is 'Final' and could not be reassigned")
+          break
+        }
+      }
+    }
+
     private fun checkFinalIsOuterMost(node: PyReferenceExpression) {
       if (isTopLevelInAnnotationOrTypeComment(node)) return
       (node.parent as? PySubscriptionExpression)?.let {
diff --git a/python/testData/inspections/PyFinalInspection/ImportedClassFinalReassignment/a.py b/python/testData/inspections/PyFinalInspection/ImportedClassFinalReassignment/a.py
index 50d82886c862..fd060b61e280 100644
--- a/python/testData/inspections/PyFinalInspection/ImportedClassFinalReassignment/a.py
+++ b/python/testData/inspections/PyFinalInspection/ImportedClassFinalReassignment/a.py
@@ -7,4 +7,7 @@ class B(A):
     def my_cls_method(cls):
         <warning descr="'a' is 'Final' and could not be reassigned">cls.a</warning> = 6
 
-<warning descr="'a' is 'Final' and could not be reassigned">B.a</warning> = 7
\ No newline at end of file
+<warning descr="'a' is 'Final' and could not be reassigned">B.a</warning> = 7
+
+class C(A):
+    <warning descr="'A.a' is 'Final' and could not be reassigned">a</warning> = 8
\ No newline at end of file
diff --git a/python/testSrc/com/jetbrains/python/inspections/PyFinalInspectionTest.java b/python/testSrc/com/jetbrains/python/inspections/PyFinalInspectionTest.java
index db2b254ca8bb..cc325b3df6c8 100644
--- a/python/testSrc/com/jetbrains/python/inspections/PyFinalInspectionTest.java
+++ b/python/testSrc/com/jetbrains/python/inspections/PyFinalInspectionTest.java
@@ -350,8 +350,10 @@ public class PyFinalInspectionTest extends PyInspectionTestCase {
                          "    def my_cls_method(cls):\n" +
                          "        <warning descr=\"'a' is 'Final' and could not be reassigned\">cls.a</warning> = 6\n" +
                          "\n" +
-                         "<warning descr=\"'a' is 'Final' and could not be reassigned\">" +
-                         "B.a</warning> = 7")
+                         "<warning descr=\"'a' is 'Final' and could not be reassigned\">B.a</warning> = 7\n" +
+                         "\n" +
+                         "class C(A):\n" +
+                         "    <warning descr=\"'A.a' is 'Final' and could not be reassigned\">a</warning> = 8\n")
     );
   }