fix: check only first sublevel for validators with each_item

changes/1933-PrettyWood.md

@@ -0,0 +1,2 @@
+**Breaking Change:** always validate only first sublevel items with `each_item`.
+There were indeed some edge cases with some compound types where the validated items were the last sublevel ones.

pydantic/fields.py

@@ -518,10 +518,26 @@ def _type_analysis(self) -> None:  # noqa: C901 (ignore complexity)
         self.sub_fields = [self._create_sub_type(self.type_, '_' + self.name)]
 
     def _create_sub_type(self, type_: Type[Any], name: str, *, for_keys: bool = False) -> 'ModelField':
+        if for_keys:
+            class_validators = None
+        else:
+            # validators for sub items should not have `each_item` as we want to check only the first sublevel
+            class_validators = {
+                k: Validator(
+                    func=v.func,
+                    pre=v.pre,
+                    each_item=False,
+                    always=v.always,
+                    check_fields=v.check_fields,
+                    skip_on_failure=v.skip_on_failure,
+                )
+                for k, v in self.class_validators.items()
+                if v.each_item
+            }
         return self.__class__(
             type_=type_,
             name=name,
-            class_validators=None if for_keys else {k: v for k, v in self.class_validators.items() if v.each_item},
+            class_validators=class_validators,
             model_config=self.model_config,
         )
 

tests/test_validators.py

@@ -575,6 +575,19 @@ def check_foobar(cls, v):
     assert Model(foobar={1: 1}).foobar == {1: 2}
 
 
+def test_validation_each_item_one_sublevel():
+    class Model(BaseModel):
+        foobar: List[Tuple[int, int]]
+
+        @validator('foobar', each_item=True)
+        def check_foobar(cls, v: Tuple[int, int]) -> Tuple[int, int]:
+            v1, v2 = v
+            assert v1 == v2
+            return v
+
+    assert Model(foobar=[(1, 1), (2, 2)]).foobar == [(1, 1), (2, 2)]
+
+
 def test_key_validation():
     class Model(BaseModel):
         foobar: Dict[int, int]