add "allow_partial" support

python/pydantic_core/_pydantic_core.pyi

@@ -91,6 +91,7 @@ class SchemaValidator:
         from_attributes: bool | None = None,
         context: Any | None = None,
         self_instance: Any | None = None,
+        allow_partial: bool = False,
     ) -> Any:
         """
         Validate a Python object against the schema and return the validated object.
@@ -105,6 +106,8 @@ class SchemaValidator:
                 [`info.context`][pydantic_core.core_schema.ValidationInfo.context].
             self_instance: An instance of a model set attributes on from validation, this is used when running
                 validation from the `__init__` method of a model.
+            allow_partial: Whether to allow partial validation, if `True` errors in the last element of sequences
+                and mappings are ignored.
 
         Raises:
             ValidationError: If validation fails.
@@ -138,6 +141,7 @@ class SchemaValidator:
         strict: bool | None = None,
         context: Any | None = None,
         self_instance: Any | None = None,
+        allow_partial: bool = False,
     ) -> Any:
         """
         Validate JSON data directly against the schema and return the validated Python object.
@@ -155,6 +159,8 @@ class SchemaValidator:
             context: The context to use for validation, this is passed to functional validators as
                 [`info.context`][pydantic_core.core_schema.ValidationInfo.context].
             self_instance: An instance of a model set attributes on from validation.
+            allow_partial: Whether to allow partial validation, if `True` errors in the last element of sequences
+                and mappings are ignored.
 
         Raises:
             ValidationError: If validation fails or if the JSON data is invalid.
@@ -163,7 +169,14 @@ class SchemaValidator:
         Returns:
             The validated Python object.
         """
-    def validate_strings(self, input: _StringInput, *, strict: bool | None = None, context: Any | None = None) -> Any:
+    def validate_strings(
+        self,
+        input: _StringInput,
+        *,
+        strict: bool | None = None,
+        context: Any | None = None,
+        allow_partial: bool = False,
+    ) -> Any:
         """
         Validate a string against the schema and return the validated Python object.
 
@@ -176,6 +189,8 @@ class SchemaValidator:
                 If `None`, the value of [`CoreConfig.strict`][pydantic_core.core_schema.CoreConfig] is used.
             context: The context to use for validation, this is passed to functional validators as
                 [`info.context`][pydantic_core.core_schema.ValidationInfo.context].
+            allow_partial: Whether to allow partial validation, if `True` errors in the last element of sequences
+                and mappings are ignored.
 
         Raises:
             ValidationError: If validation fails or if the JSON data is invalid.

python/pydantic_core/core_schema.py

@@ -122,45 +122,58 @@ class CoreConfig(TypedDict, total=False):
 
 class SerializationInfo(Protocol):
     @property
-    def include(self) -> IncExCall: ...
+    def include(self) -> IncExCall:
+        ...
 
     @property
-    def exclude(self) -> IncExCall: ...
+    def exclude(self) -> IncExCall:
+        ...
 
     @property
     def context(self) -> Any | None:
         """Current serialization context."""
 
     @property
-    def mode(self) -> str: ...
+    def mode(self) -> str:
+        ...
 
     @property
-    def by_alias(self) -> bool: ...
+    def by_alias(self) -> bool:
+        ...
 
     @property
-    def exclude_unset(self) -> bool: ...
+    def exclude_unset(self) -> bool:
+        ...
 
     @property
-    def exclude_defaults(self) -> bool: ...
+    def exclude_defaults(self) -> bool:
+        ...
 
     @property
-    def exclude_none(self) -> bool: ...
+    def exclude_none(self) -> bool:
+        ...
 
     @property
-    def serialize_as_any(self) -> bool: ...
+    def serialize_as_any(self) -> bool:
+        ...
 
-    def round_trip(self) -> bool: ...
+    def round_trip(self) -> bool:
+        ...
 
-    def mode_is_json(self) -> bool: ...
+    def mode_is_json(self) -> bool:
+        ...
 
-    def __str__(self) -> str: ...
+    def __str__(self) -> str:
+        ...
 
-    def __repr__(self) -> str: ...
+    def __repr__(self) -> str:
+        ...
 
 
 class FieldSerializationInfo(SerializationInfo, Protocol):
     @property
-    def field_name(self) -> str: ...
+    def field_name(self) -> str:
+        ...
 
 
 class ValidationInfo(Protocol):
@@ -304,7 +317,8 @@ def plain_serializer_function_ser_schema(
 
 
 class SerializerFunctionWrapHandler(Protocol):  # pragma: no cover
-    def __call__(self, input_value: Any, index_key: int | str | None = None, /) -> Any: ...
+    def __call__(self, input_value: Any, index_key: int | str | None = None, /) -> Any:
+        ...
 
 
 # (input_value: Any, serializer: SerializerFunctionWrapHandler, /) -> Any

src/errors/line_error.rs

@@ -145,6 +145,14 @@ impl ValLineError {
         self.error_type = error_type;
         self
     }
+
+    pub fn last_loc_item(&self) -> Option<&LocItem> {
+        match &self.location {
+            Location::Empty => None,
+            // first because order is reversed
+            Location::List(loc_items) => loc_items.first(),
+        }
+    }
 }
 
 #[cfg_attr(debug_assertions, derive(Debug))]

src/errors/location.rs

@@ -12,7 +12,7 @@ use crate::lookup_key::{LookupPath, PathItem};
 
 /// Used to store individual items of the error location, e.g. a string for key/field names
 /// or a number for array indices.
-#[derive(Clone)]
+#[derive(Clone, Eq, PartialEq)]
 #[cfg_attr(debug_assertions, derive(Debug))]
 pub enum LocItem {
     /// string type key, used to identify items from a dict or anything that implements `__getitem__`

src/errors/mod.rs

@@ -1,3 +1,4 @@
+use crate::validators::ValidationState;
 use pyo3::prelude::*;
 
 mod line_error;
@@ -30,3 +31,40 @@ pub fn py_err_string(py: Python, err: PyErr) -> String {
         Err(_) => "Unknown Error".to_string(),
     }
 }
+
+/// If we're in `allow_partial` mode, whether all errors occurred in the last element of the input.
+pub fn sequence_valid_as_partial(state: &ValidationState, input_length: usize, errors: &[ValLineError]) -> bool {
+    if !state.extra().allow_partial {
+        return false;
+    }
+    // for the error to be in the last element, the index of all errors must be `input_length - 1`
+    let last_index = (input_length - 1) as i64;
+    errors.iter().all(|error| {
+        if let Some(LocItem::I(loc_index)) = error.last_loc_item() {
+            *loc_index == last_index
+        } else {
+            false
+        }
+    })
+}
+
+/// If we're in `allow_partial` mode, whether all errors occurred in the last  value of the input.
+pub fn mapping_valid_as_partial(
+    state: &ValidationState,
+    opt_last_key: Option<impl Into<LocItem>>,
+    errors: &[ValLineError],
+) -> bool {
+    if !state.extra().allow_partial {
+        return false;
+    }
+    let Some(last_key) = opt_last_key.map(Into::into) else {
+        return false;
+    };
+    errors.iter().all(|error| {
+        if let Some(loc_item) = error.last_loc_item() {
+            loc_item == &last_key
+        } else {
+            false
+        }
+    })
+}

src/input/input_abstract.rs

@@ -246,6 +246,8 @@ pub trait ValidatedDict<'py> {
         &'a self,
         consumer: impl ConsumeIterator<ValResult<(Self::Key<'a>, Self::Item<'a>)>, Output = R>,
     ) -> ValResult<R>;
+    // used in partial mode to check all errors occurred in the last key value pair
+    fn last_key(&self) -> Option<Self::Key<'_>>;
 }
 
 /// For validations from a list
@@ -289,6 +291,9 @@ impl<'py> ValidatedDict<'py> for Never {
     ) -> ValResult<R> {
         unreachable!()
     }
+    fn last_key(&self) -> Option<Self::Key<'_>> {
+        unreachable!()
+    }
 }
 
 impl<'py> ValidatedList<'py> for Never {

src/input/input_json.rs

@@ -486,6 +486,10 @@ impl<'py, 'data> ValidatedDict<'py> for &'_ JsonObject<'data> {
     ) -> ValResult<R> {
         Ok(consumer.consume_iterator(LazyIndexMap::iter(self).map(|(k, v)| Ok((k.as_ref(), v)))))
     }
+
+    fn last_key(&self) -> Option<Self::Key<'_>> {
+        self.keys().last().map(AsRef::as_ref)
+    }
 }
 
 impl<'a, 'py, 'data> ValidatedList<'py> for &'a JsonArray<'data> {

src/input/input_python.rs

@@ -792,6 +792,14 @@ impl<'py> ValidatedDict<'py> for GenericPyMapping<'_, 'py> {
             Self::GetAttr(obj, _) => Ok(consumer.consume_iterator(iterate_attributes(obj)?)),
         }
     }
+
+    fn last_key(&self) -> Option<Self::Key<'_>> {
+        match self {
+            Self::Dict(dict) => dict.keys().iter().last(),
+            Self::Mapping(mapping) => mapping.keys().ok()?.iter().ok()?.last()?.ok(),
+            Self::GetAttr(_, _) => None,
+        }
+    }
 }
 
 /// Container for all the collections (sized iterable containers) types, which

src/input/input_string.rs

@@ -297,4 +297,12 @@ impl<'py> ValidatedDict<'py> for StringMappingDict<'py> {
                 .map(|(key, val)| Ok((StringMapping::new_key(key)?, StringMapping::new_value(val)?))),
         ))
     }
+
+    fn last_key(&self) -> Option<Self::Key<'_>> {
+        self.0
+            .keys()
+            .iter()
+            .last()
+            .and_then(|key| StringMapping::new_key(key).ok())
+    }
 }

src/input/return_enums.rs

@@ -17,7 +17,8 @@ use pyo3::types::{PyBytes, PyFloat, PyFrozenSet, PyIterator, PyMapping, PySet, P
 use serde::{ser::Error, Serialize, Serializer};
 
 use crate::errors::{
-    py_err_string, ErrorType, ErrorTypeDefaults, InputValue, ToErrorValue, ValError, ValLineError, ValResult,
+    py_err_string, sequence_valid_as_partial, ErrorType, ErrorTypeDefaults, InputValue, ToErrorValue, ValError,
+    ValLineError, ValResult,
 };
 use crate::py_gc::PyGcTraverse;
 use crate::tools::{extract_i64, new_py_string, py_err};
@@ -128,7 +129,9 @@ pub(crate) fn validate_iter_to_vec<'py>(
 ) -> ValResult<Vec<PyObject>> {
     let mut output: Vec<PyObject> = Vec::with_capacity(capacity);
     let mut errors: Vec<ValLineError> = Vec::new();
-    for (index, item_result) in iter.enumerate() {
+    let mut index = 0;
+    for item_result in iter {
+        index += 1;
         let item = item_result.map_err(|e| any_next_error!(py, e, max_length_check.input, index))?;
         match validator.validate(py, item.borrow_input(), state) {
             Ok(item) => {
@@ -139,15 +142,15 @@ pub(crate) fn validate_iter_to_vec<'py>(
                 max_length_check.incr()?;
                 errors.extend(line_errors.into_iter().map(|err| err.with_outer_location(index)));
                 if fail_fast {
-                    break;
+                    return Err(ValError::LineErrors(errors));
                 }
             }
             Err(ValError::Omit) => (),
             Err(err) => return Err(err),
         }
     }
 
-    if errors.is_empty() {
+    if errors.is_empty() || sequence_valid_as_partial(state, index, &errors) {
         Ok(output)
     } else {
         Err(ValError::LineErrors(errors))
@@ -197,7 +200,9 @@ pub(crate) fn validate_iter_to_set<'py>(
     fail_fast: bool,
 ) -> ValResult<()> {
     let mut errors: Vec<ValLineError> = Vec::new();
-    for (index, item_result) in iter.enumerate() {
+    let mut index = 0;
+    for item_result in iter {
+        index += 1;
         let item = item_result.map_err(|e| any_next_error!(py, e, input, index))?;
         match validator.validate(py, item.borrow_input(), state) {
             Ok(item) => {
@@ -226,11 +231,11 @@ pub(crate) fn validate_iter_to_set<'py>(
             Err(err) => return Err(err),
         }
         if fail_fast && !errors.is_empty() {
-            break;
+            return Err(ValError::LineErrors(errors));
         }
     }
 
-    if errors.is_empty() {
+    if errors.is_empty() || sequence_valid_as_partial(state, index, &errors) {
         Ok(())
     } else {
         Err(ValError::LineErrors(errors))

src/url.rs

@@ -45,7 +45,7 @@ impl PyUrl {
     pub fn py_new(py: Python, url: &Bound<'_, PyAny>) -> PyResult<Self> {
         let schema_obj = SCHEMA_DEFINITION_URL
             .get_or_init(py, || build_schema_validator(py, "url"))
-            .validate_python(py, url, None, None, None, None)?;
+            .validate_python(py, url, None, None, None, None, false)?;
         schema_obj.extract(py)
     }
 
@@ -225,7 +225,7 @@ impl PyMultiHostUrl {
     pub fn py_new(py: Python, url: &Bound<'_, PyAny>) -> PyResult<Self> {
         let schema_obj = SCHEMA_DEFINITION_MULTI_HOST_URL
             .get_or_init(py, || build_schema_validator(py, "multi-host-url"))
-            .validate_python(py, url, None, None, None, None)?;
+            .validate_python(py, url, None, None, None, None, false)?;
         schema_obj.extract(py)
     }
 

src/validators/dict.rs

@@ -3,7 +3,7 @@ use pyo3::prelude::*;
 use pyo3::types::PyDict;
 
 use crate::build_tools::is_strict;
-use crate::errors::{LocItem, ValError, ValLineError, ValResult};
+use crate::errors::{sequence_valid_as_partial, LocItem, ValError, ValLineError, ValResult};
 use crate::input::BorrowInput;
 use crate::input::ConsumeIterator;
 use crate::input::{Input, ValidatedDict};
@@ -109,8 +109,10 @@ where
     fn consume_iterator(self, iterator: impl Iterator<Item = ValResult<(Key, Value)>>) -> ValResult<PyObject> {
         let output = PyDict::new_bound(self.py);
         let mut errors: Vec<ValLineError> = Vec::new();
+        let mut input_length = 0;
 
         for item_result in iterator {
+            input_length += 1;
             let (key, value) = item_result?;
             let output_key = match self.key_validator.validate(self.py, key.borrow_input(), self.state) {
                 Ok(value) => Some(value),
@@ -140,7 +142,7 @@ where
             }
         }
 
-        if errors.is_empty() {
+        if errors.is_empty() || sequence_valid_as_partial(self.state, input_length, &errors) {
             let input = self.input;
             length_check!(input, "Dictionary", self.min_length, self.max_length, output);
             Ok(output.into())