move const validator to post validators. fixes pydantic#1410

selimb · Apr 27, 2020 · 7730a29 · 7730a29
1 parent 529130f
commit 7730a29
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Showing 3 changed files with 12 additions and 2 deletions.
diff --git a/changes/1410-selimb.md b/changes/1410-selimb.md
@@ -0,0 +1 @@
+Move `const` validator to post-validators
diff --git a/pydantic/fields.py b/pydantic/fields.py
@@ -510,11 +510,11 @@ def populate_validators(self) -> None:
             )
             self.validators = prep_validators(v_funcs)
 
-        # Add const validator
         self.pre_validators = []
         self.post_validators = []
+
         if self.field_info and self.field_info.const:
-            self.pre_validators = [make_generic_validator(constant_validator)]
+            self.post_validators.append(make_generic_validator(constant_validator))
 
         if class_validators_:
             self.pre_validators += prep_validators(v.func for v in class_validators_ if not v.each_item and v.pre)

diff --git a/tests/test_main.py b/tests/test_main.py
@@ -383,6 +383,15 @@ class Model(BaseModel):
     assert m.a == 3
 
 
+def test_const_validates_after_type_validators():
+    # issue #1410
+    class Model(BaseModel):
+        a: int = Field(3, const=True)
+
+    m = Model(a="3")
+    assert m.a == 3
+
+
 def test_const_with_wrong_value():
     class Model(BaseModel):
         a: int = Field(3, const=True)