Extended reportCallInDefaultInitializer diagnostic check to disallow list, set or dict expressions in default argument expression.

docs/configuration.md

@@ -130,7 +130,7 @@ The following settings control pyright’s diagnostic output (warnings or errors
 
 **reportInvalidTypeVarUse** [boolean or string, optional]: Generate or suppress diagnostics when a TypeVar is used inappropriately (e.g. if a TypeVar appears only once) within a generic function signature. The default value for this setting is 'none'.
 
-**reportCallInDefaultInitializer** [boolean or string, optional]: Generate or suppress diagnostics for function calls within a default value initialization expression. Such calls can mask expensive operations that are performed at module initialization time. The default value for this setting is 'none'.
+**reportCallInDefaultInitializer** [boolean or string, optional]: Generate or suppress diagnostics for function calls, list expressions, set expressions, or dictionary expressions within a default value initialization expression. Such calls can mask expensive operations that are performed at module initialization time. The default value for this setting is 'none'.
 
 **reportUnnecessaryIsInstance** [boolean or string, optional]: Generate or suppress diagnostics for 'isinstance' or 'issubclass' calls where the result is statically determined to be always true. Such calls are often indicative of a programming error. The default value for this setting is 'none'.
 

packages/pyright-internal/src/analyzer/checker.ts

@@ -31,6 +31,7 @@ import {
     CaseNode,
     ClassNode,
     DelNode,
+    DictionaryNode,
     ErrorNode,
     ExceptNode,
     FormatStringNode,
@@ -45,6 +46,7 @@ import {
     isExpressionNode,
     LambdaNode,
     ListComprehensionNode,
+    ListNode,
     MatchNode,
     MemberAccessNode,
     ModuleNode,
@@ -55,6 +57,7 @@ import {
     ParseNodeType,
     RaiseNode,
     ReturnNode,
+    SetNode,
     SliceNode,
     StatementListNode,
     StatementNode,
@@ -568,14 +571,7 @@ export class Checker extends ParseTreeWalker {
     override visitCall(node: CallNode): boolean {
         this._validateIsInstanceCall(node);
 
-        if (ParseTreeUtils.isWithinDefaultParamInitializer(node) && !this._fileInfo.isStubFile) {
-            this._evaluator.addDiagnostic(
-                this._fileInfo.diagnosticRuleSet.reportCallInDefaultInitializer,
-                DiagnosticRule.reportCallInDefaultInitializer,
-                Localizer.Diagnostic.defaultValueContainsCall(),
-                node
-            );
-        }
+        this._validateIllegalDefaultParamInitializer(node);
 
         if (
             this._fileInfo.diagnosticRuleSet.reportUnusedCallResult !== 'none' ||
@@ -638,6 +634,21 @@ export class Checker extends ParseTreeWalker {
         return true;
     }
 
+    override visitList(node: ListNode): boolean {
+        this._validateIllegalDefaultParamInitializer(node);
+        return true;
+    }
+
+    override visitSet(node: SetNode): boolean {
+        this._validateIllegalDefaultParamInitializer(node);
+        return true;
+    }
+
+    override visitDictionary(node: DictionaryNode): boolean {
+        this._validateIllegalDefaultParamInitializer(node);
+        return true;
+    }
+
     override visitListComprehension(node: ListComprehensionNode): boolean {
         this._scopedNodes.push(node);
         return true;
@@ -1120,6 +1131,19 @@ export class Checker extends ParseTreeWalker {
         return false;
     }
 
+    private _validateIllegalDefaultParamInitializer(node: ParseNode) {
+        if (this._fileInfo.diagnosticRuleSet.reportCallInDefaultInitializer !== 'none') {
+            if (ParseTreeUtils.isWithinDefaultParamInitializer(node) && !this._fileInfo.isStubFile) {
+                this._evaluator.addDiagnostic(
+                    this._fileInfo.diagnosticRuleSet.reportCallInDefaultInitializer,
+                    DiagnosticRule.reportCallInDefaultInitializer,
+                    Localizer.Diagnostic.defaultValueContainsCall(),
+                    node
+                );
+            }
+        }
+    }
+
     // Determines whether the types of the two operands for an == or != operation
     // have overlapping types.
     private _validateComparisonTypes(node: BinaryOperationNode) {

packages/pyright-internal/src/localization/package.nls.en-us.json

@@ -62,7 +62,7 @@
         "dataClassFieldWithDefault": "Fields without default values cannot appear after fields with default values",
         "declaredReturnTypePartiallyUnknown": "Declared return type, \"{returnType}\", is partially unknown",
         "declaredReturnTypeUnknown": "Declared return type is unknown",
-        "defaultValueContainsCall": "Function calls within default value initializer are not permitted",
+        "defaultValueContainsCall": "Function calls and mutable objects not allowed within parameter default value expression",
         "defaultValueNotAllowed": "Parameter with \"*\" or \"**\" cannot have default value",
         "defaultValueNotEllipsis": "Default values in stub files should be specified as \"...\"",
         "delTargetExpr": "Expression cannot be deleted",

packages/pyright-internal/src/tests/checker.test.ts

@@ -176,14 +176,14 @@ test('Mro3', () => {
 test('DefaultInitializer1', () => {
     const configOptions = new ConfigOptions('.');
 
-    // By default, optional diagnostics are ignored.
+    // By default, the reportCallInDefaultInitializer is disabled.
     let analysisResults = TestUtils.typeAnalyzeSampleFiles(['defaultInitializer1.py'], configOptions);
     TestUtils.validateResults(analysisResults, 0);
 
     // Turn on errors.
     configOptions.diagnosticRuleSet.reportCallInDefaultInitializer = 'error';
     analysisResults = TestUtils.typeAnalyzeSampleFiles(['defaultInitializer1.py'], configOptions);
-    TestUtils.validateResults(analysisResults, 2);
+    TestUtils.validateResults(analysisResults, 5);
 });
 
 test('UnnecessaryIsInstance1', () => {

packages/pyright-internal/src/tests/samples/defaultInitializer1.py

@@ -1,8 +1,9 @@
 # This sample tests the type analyzer's reporting of issues
-# with parameter default initializer expressions.
+# with parameter default initializer expressions. This is
+# covered by the reportCallInDefaultInitializer diagnostic rule.
 
 
-def foo(
+def func1(
     a=None,
     # This should generate an error
     b=dict(),
@@ -10,3 +11,16 @@ def foo(
     c=max(3, 4),
 ):
     return 3
+
+
+def func2(
+    a=None,
+    # This should generate an error
+    b={},
+    # This should generate an error
+    c=[],
+    # This should generate an error
+    d={1, 2, 3},
+    e=(1, 2, 3),
+):
+    return 3