Fix :: avoid mutating Field default value

fix pydantic#1412
PrettyWood · Apr 22, 2020 · b0f0821 · b0f0821
1 parent 1f071f1
commit b0f0821
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Showing 3 changed files with 18 additions and 2 deletions.
diff --git a/changes/1412-prettywood.md b/changes/1412-prettywood.md
@@ -0,0 +1 @@
+Avoid mutating `Field` default value
diff --git a/pydantic/fields.py b/pydantic/fields.py
@@ -302,7 +302,7 @@ def infer(
         required: 'BoolUndefined' = Undefined
         if value is Required:
             required = True
-            field_info.default = None
+            value = None
         elif value is not Undefined:
             required = False
         field_info.alias = field_info.alias or field_info_from_config.get('alias')
@@ -312,7 +312,7 @@ def infer(
             type_=annotation,
             alias=field_info.alias,
             class_validators=class_validators,
-            default=field_info.default,
+            default=value,
             default_factory=field_info.default_factory,
             required=required,
             model_config=config,

diff --git a/tests/test_main.py b/tests/test_main.py
@@ -1095,3 +1095,18 @@ class Foo(BaseModel):
         assert f.foo is None
         assert f.bar is None
         assert f.baz is None
+
+
+def test_reuse_same_field():
+    required_field = Field(...)
+
+    class Model1(BaseModel):
+        required: str = required_field
+
+    class Model2(BaseModel):
+        required: str = required_field
+
+    with pytest.raises(ValidationError):
+        Model1.parse_obj({})
+    with pytest.raises(ValidationError):
+        Model2.parse_obj({})