From 89fd2859c69fd5d684dc54a951e0579cc7fef61a Mon Sep 17 00:00:00 2001
From: Eric Traut <erictr@microsoft.com>
Date: Mon, 2 May 2022 18:51:52 -0700
Subject: [PATCH] Enhanced the reportUninitializedInstanceVariable check to
 detect cases where a class variable is declared but not initialized in the
 class body and no instance variable of the same name is assigned in the
 `__init__` method.

---
 .../pyright-internal/src/analyzer/checker.ts    | 17 ++++++++++++++++-
 .../pyright-internal/src/tests/checker.test.ts  | 13 +++++++++++++
 .../src/tests/samples/uninitializedVariable1.py | 13 +++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 packages/pyright-internal/src/tests/samples/uninitializedVariable1.py

diff --git a/packages/pyright-internal/src/analyzer/checker.ts b/packages/pyright-internal/src/analyzer/checker.ts
index b270d9018..8ef0b25c0 100644
--- a/packages/pyright-internal/src/analyzer/checker.ts
+++ b/packages/pyright-internal/src/analyzer/checker.ts
@@ -3743,10 +3743,25 @@ export class Checker extends ParseTreeWalker {
             if (
                 decls.find((decl) => {
                     const containingClass = ParseTreeUtils.getEnclosingClassOrFunction(decl.node);
-                    if (!containingClass || containingClass.nodeType === ParseNodeType.Class) {
+                    if (!containingClass) {
                         return true;
                     }
 
+                    if (containingClass.nodeType === ParseNodeType.Class) {
+                        // If this is part of an assignment statement, assume it has been
+                        // initialized as a class variable.
+                        if (decl.node.parent?.nodeType === ParseNodeType.Assignment) {
+                            return true;
+                        }
+
+                        if (
+                            decl.node.parent?.nodeType === ParseNodeType.TypeAnnotation &&
+                            decl.node.parent.parent?.nodeType === ParseNodeType.Assignment
+                        ) {
+                            return true;
+                        }
+                    }
+
                     if (containingClass.name.value === '__init__') {
                         return true;
                     }
diff --git a/packages/pyright-internal/src/tests/checker.test.ts b/packages/pyright-internal/src/tests/checker.test.ts
index 79d174937..4ee5441e0 100644
--- a/packages/pyright-internal/src/tests/checker.test.ts
+++ b/packages/pyright-internal/src/tests/checker.test.ts
@@ -413,6 +413,19 @@ test('UnusedExpression1', () => {
     TestUtils.validateResults(analysisResults, 10);
 });
 
+test('UninitializedVariable1', () => {
+    const configOptions = new ConfigOptions('.');
+
+    // By default, this is off.
+    let analysisResults = TestUtils.typeAnalyzeSampleFiles(['uninitializedVariable1.py'], configOptions);
+    TestUtils.validateResults(analysisResults, 0);
+
+    // Enable it as an error.
+    configOptions.diagnosticRuleSet.reportUninitializedInstanceVariable = 'error';
+    analysisResults = TestUtils.typeAnalyzeSampleFiles(['uninitializedVariable1.py'], configOptions);
+    TestUtils.validateResults(analysisResults, 1);
+});
+
 // For now, this functionality is disabled.
 
 // test('Deprecated1', () => {
diff --git a/packages/pyright-internal/src/tests/samples/uninitializedVariable1.py b/packages/pyright-internal/src/tests/samples/uninitializedVariable1.py
new file mode 100644
index 000000000..ef26681b4
--- /dev/null
+++ b/packages/pyright-internal/src/tests/samples/uninitializedVariable1.py
@@ -0,0 +1,13 @@
+# This sample tests the reportUninitializedInstanceVariable functionality.
+
+class A:
+    # This should generate an error if reportUninitializedInstanceVariable
+    # is enabled.
+    v1: int
+    v2: int
+    v3 = 2
+    v4: int = 3
+
+    def __init__(self) -> None:
+        self.v2 = 3
+        super().__init__()