Fix dataclass plugin interaction with member expressions (python#6739)

ilevkivskyi · web-flow · commit e8a72a024388 · 2019-04-29T19:34:32.000-07:00
Fixes python#6516 It also fixes minor corner case that affects tests cases proposed in the issue.
diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
@@ -3,7 +3,7 @@
 
 from mypy.nodes import (
     ARG_OPT, ARG_POS, MDEF, Argument, AssignmentStmt, CallExpr,
-    Context, Expression, FuncDef, JsonDict, NameExpr,
+    Context, Expression, FuncDef, JsonDict, NameExpr, RefExpr,
     SymbolTableNode, TempNode, TypeInfo, Var, TypeVarExpr
 )
 from mypy.plugin import ClassDefContext
@@ -300,7 +300,7 @@ def collect_attributes(self) -> List[DataclassAttribute]:
                     Context(line=attr.line, column=attr.column),
                 )
 
-            found_default = found_default or attr.has_default
+            found_default = found_default or (attr.has_default and attr.is_in_init)
 
         return all_attrs
 
@@ -337,7 +337,7 @@ def _collect_field_args(expr: Expression) -> Tuple[bool, Dict[str, Expression]]:
     """
     if (
             isinstance(expr, CallExpr) and
-            isinstance(expr.callee, NameExpr) and
+            isinstance(expr.callee, RefExpr) and
             expr.callee.fullname == 'dataclasses.field'
     ):
         # field() only takes keyword arguments.
diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
@@ -586,3 +586,22 @@ class B:
 
 reveal_type(B)  # E: Revealed type is 'def (x: Any) -> __main__.B'
 [builtins fixtures/list.pyi]
+
+[case testMemberExprWorksAsField]
+import dataclasses
+
+@dataclasses.dataclass
+class A:
+    x: int = dataclasses.field(metadata={"doc": "foo"})
+    y: str
+
+@dataclasses.dataclass
+class B:
+    x: int = dataclasses.field(init=False, default=1)
+    y: str
+
+@dataclasses.dataclass
+class C:
+    x: int = dataclasses.field(default=1)
+    y: str = dataclasses.field(metadata={"doc": "foo"})  # E: Attributes without a default cannot follow attributes with one
+[builtins fixtures/dict.pyi]
