From 7730a29aa3c5cb8565c54d1dd5427f8de04ecb59 Mon Sep 17 00:00:00 2001
From: Selim Belhaouane <selim.belhaouane@gmail.com>
Date: Mon, 27 Apr 2020 15:19:38 -0400
Subject: [PATCH] move const validator to post validators. fixes #1410

---
 changes/1410-selimb.md | 1 +
 pydantic/fields.py     | 4 ++--
 tests/test_main.py     | 9 +++++++++
 3 files changed, 12 insertions(+), 2 deletions(-)
 create mode 100644 changes/1410-selimb.md

diff --git a/changes/1410-selimb.md b/changes/1410-selimb.md
new file mode 100644
index 00000000000..8ebdaaeda75
--- /dev/null
+++ b/changes/1410-selimb.md
@@ -0,0 +1 @@
+Move `const` validator to post-validators
\ No newline at end of file
diff --git a/pydantic/fields.py b/pydantic/fields.py
index c4445871224..c49ad7f0470 100644
--- 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
index 71371d3bccb..8a054c36938 100644
--- 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)