<!-- Thank you for your contribution! -->
<!-- Unless your change is trivial, please create an issue to discuss the change before creating a PR -->

## Change Summary

I noticed similar or identical logic in several places and extracted a couple of methods to reduce duplication.

The two commits are fairly independent and it may be easier to view their diffs separately to understand the changes. The first is probably a bit more compelling.

Note that the original code replaced by `clean_schema` wasn't always exactly the same, but the differences didn't really strike me as intentional, and either way it seemed good to draw attention to those differences and consider discussing them or adding comments to clarify.

## Related issue number

There's no issue because this isn't fixing/adding anything notable, it's just refactoring. I thought it made more sense to discuss the changes here rather than in a separate issue.

## Checklist

* [x] The pull request title is a good summary of the changes - it will be used in the changelog
* [x] Unit tests for the changes exist
* [x] Tests pass on CI
* [x] Documentation reflects the changes where applicable
* [x] My PR is ready to review, **please add a comment including the phrase "please review" to assign reviewers**


Selected Reviewer: @adriangb
Refactoring schema-related code. <!-- Thank you for your contribution! -->
<!-- Unless your change is trivial, please create an issue to discuss the change before creating a PR -->

## Change Summary

I noticed similar or identical logic in several places and extracted a couple of methods to reduce duplication.

The two commits are fairly independent and it may be easier to view their diffs separately to understand the changes. The first is probably a bit more compelling.

Note that the original code replaced by `clean_schema` wasn't always exactly the same, but the differences didn't really strike me as intentional, and either way it seemed good to draw attention to those differences and consider discussing them or adding comments to clarify.

## Related issue number

There's no issue because this isn't fixing/adding anything notable, it's just refactoring. I thought it made more sense to discuss the changes here rather than in a separate issue.

## Checklist

* [x] The pull request title is a good summary of the changes - it will be used in the changelog
* [x] Unit tests for the changes exist
* [x] Tests pass on CI
* [x] Documentation reflects the changes where applicable
* [x] My PR is ready to review, **please add a comment including the phrase "please review" to assign reviewers**


Selected Reviewer: @adriangb
import json
from typing import TYPE_CHECKING, Any, Dict, Generator, List, Optional, Sequence, Tuple, Type, Union

from .json import pydantic_encoder
from .utils import Representation

if TYPE_CHECKING:
    from typing_extensions import TypedDict

    from .config import BaseConfig
    from .types import ModelOrDc
    from .typing import ReprArgs

    Loc = Tuple[Union[int, str], ...]

    class _ErrorDictRequired(TypedDict):
        loc: Loc
        msg: str
        type: str

    class ErrorDict(_ErrorDictRequired, total=False):
        ctx: Dict[str, Any]


__all__ = 'ErrorWrapper', 'ValidationError'


class ErrorWrapper(Representation):
    __slots__ = 'exc', '_loc'

    def __init__(self, exc: Exception, loc: Union[str, 'Loc']) -> None:
        self.exc = exc
        self._loc = loc

    def loc_tuple(self) -> 'Loc':
        if isinstance(self._loc, tuple):
            return self._loc
        else:
            return (self._loc,)

    def __repr_args__(self) -> 'ReprArgs':
        return [('exc', self.exc), ('loc', self.loc_tuple())]


# ErrorList is something like Union[List[Union[List[ErrorWrapper], ErrorWrapper]], ErrorWrapper]
# but recursive, therefore just use:
ErrorList = Union[Sequence[Any], ErrorWrapper]


class ValidationError(Representation, ValueError):
    __slots__ = 'raw_errors', 'model', '_error_cache'

    def __init__(self, errors: Sequence[ErrorList], model: 'ModelOrDc') -> None:
        self.raw_errors = errors
        self.model = model
        self._error_cache: Optional[List['ErrorDict']] = None

    def errors(self) -> List['ErrorDict']:
        if self._error_cache is None:
            try:
                config = self.model.__config__  # type: ignore
            except AttributeError:
                config = self.model.__pydantic_model__.__config__  # type: ignore
            self._error_cache = list(flatten_errors(self.raw_errors, config))
        return self._error_cache

    def json(self, *, indent: Union[None, int, str] = 2) -> str:
        return json.dumps(self.errors(), indent=indent, default=pydantic_encoder)

    def __str__(self) -> str:
        errors = self.errors()
        no_errors = len(errors)
        return (
            f'{no_errors} validation error{"" if no_errors == 1 else "s"} for {self.model.__name__}\n'
            f'{display_errors(errors)}'
        )

    def __repr_args__(self) -> 'ReprArgs':
        return [('model', self.model.__name__), ('errors', self.errors())]


def display_errors(errors: List['ErrorDict']) -> str:
    return '\n'.join(f'{_display_error_loc(e)}\n  {e["msg"]} ({_display_error_type_and_ctx(e)})' for e in errors)


def _display_error_loc(error: 'ErrorDict') -> str:
    return ' -> '.join(str(e) for e in error['loc'])


def _display_error_type_and_ctx(error: 'ErrorDict') -> str:
    t = 'type=' + error['type']
    ctx = error.get('ctx')
    if ctx:
        return t + ''.join(f'; {k}={v}' for k, v in ctx.items())
    else:
        return t


def flatten_errors(
    errors: Sequence[Any], config: Type['BaseConfig'], loc: Optional['Loc'] = None
) -> Generator['ErrorDict', None, None]:
    for error in errors:
        if isinstance(error, ErrorWrapper):

            if loc:
                error_loc = loc + error.loc_tuple()
            else:
                error_loc = error.loc_tuple()

            if isinstance(error.exc, ValidationError):
                yield from flatten_errors(error.exc.raw_errors, config, error_loc)
            else:
                yield error_dict(error.exc, config, error_loc)
        elif isinstance(error, list):
            yield from flatten_errors(error, config, loc=loc)
        else:
            raise RuntimeError(f'Unknown error object: {error}')


def error_dict(exc: Exception, config: Type['BaseConfig'], loc: 'Loc') -> 'ErrorDict':
    type_ = get_exc_type(exc.__class__)
    msg_template = config.error_msg_templates.get(type_) or getattr(exc, 'msg_template', None)
    ctx = exc.__dict__
    if msg_template:
        msg = msg_template.format(**ctx)
    else:
        msg = str(exc)

    d: 'ErrorDict' = {'loc': loc, 'msg': msg, 'type': type_}

    if ctx:
        d['ctx'] = ctx

    return d


_EXC_TYPE_CACHE: Dict[Type[Exception], str] = {}


def get_exc_type(cls: Type[Exception]) -> str:
    # slightly more efficient than using lru_cache since we don't need to worry about the cache filling up
    try:
        return _EXC_TYPE_CACHE[cls]
    except KeyError:
        r = _get_exc_type(cls)
        _EXC_TYPE_CACHE[cls] = r
        return r


def _get_exc_type(cls: Type[Exception]) -> str:
    if issubclass(cls, AssertionError):
        return 'assertion_error'

    base_name = 'type_error' if issubclass(cls, TypeError) else 'value_error'
    if cls in (TypeError, ValueError):
        # just TypeError or ValueError, no extra code
        return base_name

    # if it's not a TypeError or ValueError, we just take the lowercase of the exception name
    # no chaining or snake case logic, use "code" for more complex error types.
    code = getattr(cls, 'code', None) or cls.__name__.replace('Error', '').lower()
    return base_name + '.' + code

import json
from typing import TYPE_CHECKING, Any, Dict, Generator, List, Optional, Sequence, Tuple, Type, Union

from .json import pydantic_encoder
from .utils import Representation

if TYPE_CHECKING:
    from typing_extensions import TypedDict

    from .config import BaseConfig
    from .types import ModelOrDc
    from .typing import ReprArgs

    Loc = Tuple[Union[int, str], ...]

    class _ErrorDictRequired(TypedDict):
        loc: Loc
        msg: str
        type: str

    class ErrorDict(_ErrorDictRequired, total=False):
        ctx: Dict[str, Any]


__all__ = 'ErrorWrapper', 'ValidationError'


class ErrorWrapper(Representation):
    __slots__ = 'exc', '_loc'

    def __init__(self, exc: Exception, loc: Union[str, 'Loc']) -> None:
        self.exc = exc
        self._loc = loc

    def loc_tuple(self) -> 'Loc':
        if isinstance(self._loc, tuple):
            return self._loc
        else:
            return (self._loc,)

    def __repr_args__(self) -> 'ReprArgs':
        return [('exc', self.exc), ('loc', self.loc_tuple())]


# ErrorList is something like Union[List[Union[List[ErrorWrapper], ErrorWrapper]], ErrorWrapper]
# but recursive, therefore just use:
ErrorList = Union[Sequence[Any], ErrorWrapper]


class ValidationError(Representation, ValueError):
    __slots__ = 'raw_errors', 'model', '_error_cache'

    def __init__(self, errors: Sequence[ErrorList], model: 'ModelOrDc') -> None:
        self.raw_errors = errors
        self.model = model
        self._error_cache: Optional[List['ErrorDict']] = None

    def errors(self) -> List['ErrorDict']:
        if self._error_cache is None:
            try:
                config = self.model.__config__  # type: ignore
            except AttributeError:
                config = self.model.__pydantic_model__.__config__  # type: ignore
            self._error_cache = list(flatten_errors(self.raw_errors, config))
        return self._error_cache

    def json(self, *, indent: Union[None, int, str] = 2) -> str:
        return json.dumps(self.errors(), indent=indent, default=pydantic_encoder)

    def __str__(self) -> str:
        errors = self.errors()
        no_errors = len(errors)
        return (
            f'{no_errors} validation error{"" if no_errors == 1 else "s"} for {self.model.__name__}\n'
            f'{display_errors(errors)}'
        )

    def __repr_args__(self) -> 'ReprArgs':
        return [('model', self.model.__name__), ('errors', self.errors())]


def display_errors(errors: List['ErrorDict']) -> str:
    return '\n'.join(f'{_display_error_loc(e)}\n  {e["msg"]} ({_display_error_type_and_ctx(e)})' for e in errors)


def _display_error_loc(error: 'ErrorDict') -> str:
    return ' -> '.join(str(e) for e in error['loc'])


def _display_error_type_and_ctx(error: 'ErrorDict') -> str:
    t = 'type=' + error['type']
    ctx = error.get('ctx')
    if ctx:
        return t + ''.join(f'; {k}={v}' for k, v in ctx.items())
    else:
        return t


def flatten_errors(
    errors: Sequence[Any], config: Type['BaseConfig'], loc: Optional['Loc'] = None
) -> Generator['ErrorDict', None, None]:
    for error in errors:
        if isinstance(error, ErrorWrapper):

            if loc:
                error_loc = loc + error.loc_tuple()
            else:
                error_loc = error.loc_tuple()

            if isinstance(error.exc, ValidationError):
                yield from flatten_errors(error.exc.raw_errors, config, error_loc)
            else:
                yield error_dict(error.exc, config, error_loc)
        elif isinstance(error, list):
            yield from flatten_errors(error, config, loc=loc)
        else:
            raise RuntimeError(f'Unknown error object: {error}')


def error_dict(exc: Exception, config: Type['BaseConfig'], loc: 'Loc') -> 'ErrorDict':
    type_ = get_exc_type(exc.__class__)
    msg_template = config.error_msg_templates.get(type_) or getattr(exc, 'msg_template', None)
    ctx = exc.__dict__
    if msg_template:
        msg = msg_template.format(**ctx)
    else:
        msg = str(exc)

    d: 'ErrorDict' = {'loc': loc, 'msg': msg, 'type': type_}

    if ctx:
        d['ctx'] = ctx

    return d


_EXC_TYPE_CACHE: Dict[Type[Exception], str] = {}


def get_exc_type(cls: Type[Exception]) -> str:
    # slightly more efficient than using lru_cache since we don't need to worry about the cache filling up
    try:
        return _EXC_TYPE_CACHE[cls]
    except KeyError:
        r = _get_exc_type(cls)
        _EXC_TYPE_CACHE[cls] = r
        return r


def _get_exc_type(cls: Type[Exception]) -> str:
    if issubclass(cls, AssertionError):
        return 'assertion_error'

    base_name = 'type_error' if issubclass(cls, TypeError) else 'value_error'
    if cls in (TypeError, ValueError):
        # just TypeError or ValueError, no extra code
        return base_name

    # if it's not a TypeError or ValueError, we just take the lowercase of the exception name
    # no chaining or snake case logic, use "code" for more complex error types.
    code = getattr(cls, 'code', None) or cls.__name__.replace('Error', '').lower()
    return base_name + '.' + code
