Don't define a duplicate __init__ for dataclasses

Closes #6399.
python · Jul 8, 2019 · c5288f9 · c5288f9
1 parent 18a9fe1
commit c5288f9
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
@@ -92,7 +92,7 @@ def transform(self) -> None:
             'frozen': _get_decorator_bool_argument(self._ctx, 'frozen', False),
         }
 
-        if decorator_arguments['init']:
+        if decorator_arguments['init'] and info.get('__init__') is None:
             add_method(
                 ctx,
                 '__init__',

diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
@@ -16,6 +16,21 @@ Person('Jonh', 21, None)  # E: Too many arguments for "Person"
 
 [builtins fixtures/list.pyi]
 
+[case testDataclassesCustomInit]
+# flags: --python-version 3.6
+from dataclasses import dataclass
+
+@dataclass
+class A:
+    a: int
+
+    def __init__(self, a: str) -> None:
+        pass
+
+A('1')
+
+[builtins fixtures/list.pyi]
+
 [case testDataclassesBasicInheritance]
 # flags: --python-version 3.6
 from dataclasses import dataclass