fix: check only first sublevel for validators with each_item (#1991)

* fix: check only first sublevel for validators with `each_item`

When using a validator with `each_item`, the items are all validated
one by one. But if the items are also iterable the subitems would then
be validated because the validator would be kept as it is.
Now the validator passed to the items is changed and won't be propagated

closes #1933

* chore: add breaking change

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]