Don't create descriptor for symmetric converters

microsoft · Jun 20, 2023 · 9c0b2c5 · 9c0b2c5
1 parent 1315572
commit 9c0b2c5
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Showing 3 changed files with 29 additions and 19 deletions.
diff --git a/packages/pyright-internal/src/analyzer/dataClasses.ts b/packages/pyright-internal/src/analyzer/dataClasses.ts
@@ -49,6 +49,7 @@ import {
     isFunction,
     isInstantiableClass,
     isOverloadedFunction,
+    isTypeSame,
     NoneType,
     OverloadedFunctionType,
     TupleTypeArgument,
@@ -516,17 +517,20 @@ export function synthesizeDataClassMethods(
                     if (entry.converter) {
                         const fieldType = effectiveType;
                         effectiveType = getConverterInputType(evaluator, entry.converter, effectiveType, entry.name);
-                        symbolTable.set(
-                            entry.name,
-                            getDescriptorForConverterField(
-                                evaluator,
-                                node,
-                                entry.converter,
+
+                        if (!isTypeSame(fieldType, effectiveType)) {
+                            symbolTable.set(
                                 entry.name,
-                                fieldType,
-                                effectiveType
-                            )
-                        );
+                                getDescriptorForConverterField(
+                                    evaluator,
+                                    node,
+                                    entry.converter,
+                                    entry.name,
+                                    fieldType,
+                                    effectiveType
+                                )
+                            );
+                        }
                     }
 
                     const effectiveName = entry.alias || entry.name;

diff --git a/packages/pyright-internal/src/tests/samples/dataclassConverter2.py b/packages/pyright-internal/src/tests/samples/dataclassConverter2.py
@@ -4,18 +4,24 @@
 from dataclasses import dataclass, field
 
 
-def converter_simple(s: str) -> int:
-    return int(s)
-
+def converter_simple(s: str) -> int: ...
+def converter_passThru(x: str | int) -> str | int: ...
 
 @dataclass
 class Foo:
     # This should generate an error because "converter" is not an official property yet.
-    field0: int = field(converter=converter_simple)
+    asymmetric: int = field(converter=converter_simple)
+    # This should generate an error because "converter" is not an official property yet.
+    symmetric: str | int = field(converter=converter_passThru)
 
-foo = Foo("1")
-reveal_type(foo.field0, expected_text="int")
-foo.field0 = "2"
+foo = Foo("1", 1)
 
+reveal_type(foo.asymmetric, expected_text="int")
+foo.asymmetric = "2"
+reveal_type(foo.asymmetric, expected_text="int") # Asymmetric -- type narrowing should not occur
 # This should generate an error because only strs can be assigned to field0.
-foo.field0 = 2
+foo.asymmetric = 2
+
+reveal_type(foo.symmetric, expected_text="str | int")
+foo.symmetric = "1"
+reveal_type(foo.symmetric, expected_text="Literal['1']") # Symmetric -- type narrowing should occur
diff --git a/packages/pyright-internal/src/tests/typeEvaluator4.test.ts b/packages/pyright-internal/src/tests/typeEvaluator4.test.ts
@@ -682,7 +682,7 @@ test('DataClassConverter1', () => {
 test('DataClassConverter2', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['dataclassConverter2.py']);
 
-    TestUtils.validateResults(analysisResults, 2);
+    TestUtils.validateResults(analysisResults, 3);
 });
 
 test('DataClassPostInit1', () => {