Fix strict behavior for unions (#1638)

Author: sydney-runkle

python/pydantic_core/core_schema.py

@@ -2525,7 +2525,6 @@ def union_schema(
     custom_error_message: str | None = None,
     custom_error_context: dict[str, str | int] | None = None,
     mode: Literal['smart', 'left_to_right'] | None = None,
-    strict: bool | None = None,
     ref: str | None = None,
     metadata: dict[str, Any] | None = None,
     serialization: SerSchema | None = None,
@@ -2551,7 +2550,6 @@ def union_schema(
         mode: How to select which choice to return
             * `smart` (default) will try to return the choice which is the closest match to the input value
             * `left_to_right` will return the first choice in `choices` which succeeds validation
-        strict: Whether the underlying schemas should be validated with strict mode
         ref: optional unique identifier of the schema, used to reference the schema in other places
         metadata: Any other information you want to include with the schema, not used by pydantic-core
         serialization: Custom serialization schema
@@ -2564,7 +2562,6 @@ def union_schema(
         custom_error_message=custom_error_message,
         custom_error_context=custom_error_context,
         mode=mode,
-        strict=strict,
         ref=ref,
         metadata=metadata,
         serialization=serialization,

src/validators/union.rs

@@ -8,7 +8,7 @@ use pyo3::{intern, PyTraverseError, PyVisit};
 use smallvec::SmallVec;
 
 use crate::build_tools::py_schema_err;
-use crate::build_tools::{is_strict, schema_or_config};
+use crate::build_tools::schema_or_config;
 use crate::common::union::{Discriminator, SMALL_UNION_THRESHOLD};
 use crate::errors::{ErrorType, ToErrorValue, ValError, ValLineError, ValResult};
 use crate::input::{BorrowInput, Input, ValidatedDict};
@@ -43,7 +43,6 @@ pub struct UnionValidator {
     mode: UnionMode,
     choices: Vec<(CombinedValidator, Option<String>)>,
     custom_error: Option<CustomError>,
-    strict: bool,
     name: String,
 }
 
@@ -91,7 +90,6 @@ impl BuildValidator for UnionValidator {
                     mode,
                     choices,
                     custom_error: CustomError::build(schema, config, definitions)?,
-                    strict: is_strict(schema, config)?,
                     name: format!("{}[{descr}]", Self::EXPECTED_TYPE),
                 }
                 .into())
@@ -110,17 +108,11 @@ impl UnionValidator {
         let old_exactness = state.exactness;
         let old_fields_set_count = state.fields_set_count;
 
-        let strict = state.strict_or(self.strict);
         let mut errors = MaybeErrors::new(self.custom_error.as_ref());
 
         let mut best_match: Option<(Py<PyAny>, Exactness, Option<usize>)> = None;
 
         for (choice, label) in &self.choices {
-            let state = &mut state.rebind_extra(|extra| {
-                if strict {
-                    extra.strict = Some(strict);
-                }
-            });
             state.exactness = Some(Exactness::Exact);
             state.fields_set_count = None;
             let result = choice.validate(py, input, state);
@@ -197,14 +189,6 @@ impl UnionValidator {
     ) -> ValResult<PyObject> {
         let mut errors = MaybeErrors::new(self.custom_error.as_ref());
 
-        let mut rebound_state;
-        let state = if state.strict_or(self.strict) {
-            rebound_state = state.rebind_extra(|extra| extra.strict = Some(true));
-            &mut rebound_state
-        } else {
-            state
-        };
-
         for (validator, label) in &self.choices {
             match validator.validate(py, input, state) {
                 Err(ValError::LineErrors(lines)) => errors.push(validator, label.as_deref(), lines),
@@ -300,7 +284,6 @@ pub struct TaggedUnionValidator {
     discriminator: Discriminator,
     lookup: LiteralLookup<CombinedValidator>,
     from_attributes: bool,
-    strict: bool,
     custom_error: Option<CustomError>,
     tags_repr: String,
     discriminator_repr: String,
@@ -349,7 +332,6 @@ impl BuildValidator for TaggedUnionValidator {
             discriminator,
             lookup,
             from_attributes,
-            strict: is_strict(schema, config)?,
             custom_error: CustomError::build(schema, config, definitions)?,
             tags_repr,
             discriminator_repr,
@@ -371,7 +353,7 @@ impl Validator for TaggedUnionValidator {
         match &self.discriminator {
             Discriminator::LookupKey(lookup_key) => {
                 let from_attributes = state.extra().from_attributes.unwrap_or(self.from_attributes);
-                let dict = input.validate_model_fields(self.strict, from_attributes)?;
+                let dict = input.validate_model_fields(state.strict_or(false), from_attributes)?;
                 // note this methods returns PyResult<Option<(data, data)>>, the outer Err is just for
                 // errors when getting attributes which should be "raised"
                 let tag = match dict.get_item(lookup_key)? {

tests/benchmarks/test_micro_benchmarks.py

@@ -686,16 +686,18 @@ def test_smart_union_coerce_core(self, benchmark):
     def test_strict_union_core(self, benchmark):
         v = SchemaValidator(
             schema=core_schema.union_schema(
-                strict=True, choices=[core_schema.bool_schema(), core_schema.int_schema(), core_schema.str_schema()]
-            )
+                choices=[core_schema.bool_schema(), core_schema.int_schema(), core_schema.str_schema()]
+            ),
+            config=CoreConfig(strict=True),
         )
 
         benchmark(v.validate_python, 1)
 
     @pytest.mark.benchmark(group='strict-union-error')
     def test_strict_union_error_core(self, benchmark):
         v = SchemaValidator(
-            schema=core_schema.union_schema(strict=True, choices=[core_schema.bool_schema(), core_schema.str_schema()])
+            schema=core_schema.union_schema(choices=[core_schema.bool_schema(), core_schema.str_schema()]),
+            config=CoreConfig(strict=True),
         )
 
         def validate_with_expected_error():

tests/validators/test_bytes.py

@@ -91,7 +91,7 @@ def test_constrained_bytes(py_and_json: PyAndJson, opts: dict[str, Any], input,
 
 
 def test_union():
-    v = SchemaValidator(cs.union_schema(choices=[cs.str_schema(), cs.bytes_schema()], strict=True))
+    v = SchemaValidator(cs.union_schema(choices=[cs.str_schema(strict=True), cs.bytes_schema(strict=True)]))
     assert v.validate_python('oh, a string') == 'oh, a string'
     assert v.validate_python(b'oh, bytes') == b'oh, bytes'
 

tests/validators/test_definitions_recursive.py

@@ -611,11 +611,11 @@ def test_union_cycle(strict: bool):
                                 'foobar': core_schema.typed_dict_field(
                                     core_schema.list_schema(core_schema.definition_reference_schema('root-schema'))
                                 )
-                            }
+                            },
+                            strict=strict,
                         )
                     ],
                     auto_collapse=False,
-                    strict=strict,
                     ref='root-schema',
                 )
             ],
@@ -700,11 +700,11 @@ def f(input_value, info):
                         )
                     ],
                     auto_collapse=False,
-                    strict=strict,
                     ref='root-schema',
                 )
             ],
-        )
+        ),
+        config=CoreConfig(strict=strict),
     )
 
     with pytest.raises(ValidationError) as exc_info:

tests/validators/test_union.py

@@ -8,7 +8,7 @@
 import pytest
 from dirty_equals import IsFloat, IsInt
 
-from pydantic_core import SchemaError, SchemaValidator, ValidationError, core_schema, validate_core_schema
+from pydantic_core import CoreConfig, SchemaError, SchemaValidator, ValidationError, core_schema, validate_core_schema
 
 from ..conftest import plain_repr
 
@@ -262,16 +262,47 @@ def test_one_choice():
     assert v.validate_python('hello') == 'hello'
 
 
-def test_strict_union():
+def test_strict_union_flag() -> None:
+    v = SchemaValidator(core_schema.union_schema(choices=[core_schema.bool_schema(), core_schema.int_schema()]))
+    assert v.validate_python(1, strict=True) == 1
+    assert v.validate_python(123, strict=True) == 123
+
+    with pytest.raises(ValidationError) as exc_info:
+        v.validate_python('123', strict=True)
+
+    assert exc_info.value.errors(include_url=False) == [
+        {'type': 'bool_type', 'loc': ('bool',), 'msg': 'Input should be a valid boolean', 'input': '123'},
+        {'type': 'int_type', 'loc': ('int',), 'msg': 'Input should be a valid integer', 'input': '123'},
+    ]
+
+
+def test_strict_union_config_level() -> None:
     v = SchemaValidator(
-        core_schema.union_schema(strict=True, choices=[core_schema.bool_schema(), core_schema.int_schema()])
+        core_schema.union_schema(choices=[core_schema.bool_schema(), core_schema.int_schema()]),
+        config=CoreConfig(strict=True),
     )
+
     assert v.validate_python(1) == 1
     assert v.validate_python(123) == 123
 
     with pytest.raises(ValidationError) as exc_info:
         v.validate_python('123')
+    assert exc_info.value.errors(include_url=False) == [
+        {'type': 'bool_type', 'loc': ('bool',), 'msg': 'Input should be a valid boolean', 'input': '123'},
+        {'type': 'int_type', 'loc': ('int',), 'msg': 'Input should be a valid integer', 'input': '123'},
+    ]
 
+
+def test_strict_union_member_level() -> None:
+    v = SchemaValidator(
+        core_schema.union_schema(choices=[core_schema.bool_schema(strict=True), core_schema.int_schema(strict=True)])
+    )
+
+    assert v.validate_python(1) == 1
+    assert v.validate_python(123) == 123
+
+    with pytest.raises(ValidationError) as exc_info:
+        v.validate_python('123')
     assert exc_info.value.errors(include_url=False) == [
         {'type': 'bool_type', 'loc': ('bool',), 'msg': 'Input should be a valid boolean', 'input': '123'},
         {'type': 'int_type', 'loc': ('int',), 'msg': 'Input should be a valid integer', 'input': '123'},
@@ -469,10 +500,10 @@ def test_left_to_right_union():
 
 
 def test_left_to_right_union_strict():
-    choices = [core_schema.int_schema(), core_schema.float_schema()]
+    choices = [core_schema.int_schema(strict=True), core_schema.float_schema(strict=True)]
 
     # left_to_right union will select not cast if int first (strict int will not accept float)
-    v = SchemaValidator(core_schema.union_schema(choices, mode='left_to_right', strict=True))
+    v = SchemaValidator(core_schema.union_schema(choices, mode='left_to_right'))
     out = v.validate_python(1)
     assert out == 1
     assert isinstance(out, int)
@@ -482,7 +513,12 @@ def test_left_to_right_union_strict():
     assert isinstance(out, float)
 
     # reversing union will select float always (as strict float will accept int)
-    v = SchemaValidator(core_schema.union_schema(list(reversed(choices)), mode='left_to_right', strict=True))
+    v = SchemaValidator(
+        core_schema.union_schema(
+            list(reversed(choices)),
+            mode='left_to_right',
+        )
+    )
     out = v.validate_python(1.0)
     assert out == 1.0
     assert isinstance(out, float)