19686422763

Committed 25 Nov 2025 10:47PM UTC coverage: 93.933% (+0.005%) from 93.928%

Build # 19686422763

Build Type

Pull #1265

github

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web-flow

Commit Message

Merge e0a8ef6a2 into 38734420f

Pull Request Pull Request #1265: Extending AccumulationTable context manager to support multiple loop evaluations

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/python_ta/contracts/__init__.py

"""This module provides the functionality for PythonTA contracts.

Representation invariants, preconditions, and postconditions are parsed, compiled, and stored.
Below are some notes on how they are stored.
    - Representation invariants are stored in a class attribute __representation_invariants__
    as a list [(assertion, compiled)].
    - Preconditions are stored in an attribute __preconditions__ of the function as a list
    [(assertion, compiled)].
    - Postconditions are stored in an attribute __postconditions__ of the function as a list
    [(assertion, compiled, return_val_var_name)].
"""

from __future__ import annotations

import inspect
import logging
import re
import sys
import typing
from types import CodeType, FunctionType, ModuleType
from typing import (
    Any,
    Callable,
    Optional,
    TypeVar,
    Union,
    get_args,
    get_origin,
    overload,
)

import wrapt
from typeguard import CollectionCheckStrategy, TypeCheckError, check_type

# Configuration options

ENABLE_CONTRACT_CHECKING = True
"""
Set to True to enable contract checking.
"""

DEBUG_CONTRACTS = False
"""
Set to True to display debugging messages when checking contracts.
"""

RENAME_MAIN_TO_PYDEV_UMD = True
"""
Set to False to disable workaround for PyCharm's "Run File in Python Console" action.
In most cases you should not need to change this!
"""

STRICT_NUMERIC_TYPES = True
"""
Set to False to allow more specific numeric types to be accepted by more general type annotations.
"""

_PYDEV_UMD_NAME = "pydev_umd"


_DEFAULT_MAX_VALUE_LENGTH = 30
FUNCTION_RETURN_VALUE = "$return_value"


class PyTAContractError(Exception):
    """Error raised when a PyTA contract assertion is violated."""


def check_all_contracts(*mod_names: str, decorate_main: bool = True) -> None:
    """Automatically check contracts for all functions and classes in the given modules.

    By default (when called with no arguments), the current module is used.

    Args:
        *mod_names: The names of modules to check contracts for. These modules must have been
            previously imported.
        decorate_main: True if the module being run (where __name__ == '__main__') should
            have contracts checked.
    """
    if not ENABLE_CONTRACT_CHECKING:
        return

    modules = []
    if decorate_main:
        mod_names = mod_names + ("__main__",)

        # Also add _PYDEV_UMD_NAME, handling when the file is being run in PyCharm
        # with the "Run in Python Console" action.
        if RENAME_MAIN_TO_PYDEV_UMD:
            mod_names = mod_names + (_PYDEV_UMD_NAME,)

    for module_name in mod_names:
        modules.append(sys.modules.get(module_name, None))

    for module in modules:
        if not module:
            # Module name was passed in incorrectly.
            continue
        for name, value in inspect.getmembers(module):
            if inspect.isfunction(value) or inspect.isclass(value):
                module.__dict__[name] = check_contracts(value, module_names=set(mod_names))


# Wildcard Type Variable
Class = TypeVar("Class", bound=type)


@overload
def check_contracts(
    func: FunctionType,
    module_names: Optional[set[str]] = None,
    argument_types: bool = True,
    return_type: bool = True,
    preconditions: bool = True,
    postconditions: bool = True,
) -> FunctionType: ...


@overload
def check_contracts(
    func: Class,
    module_names: Optional[set[str]] = None,
    argument_types: bool = True,
    return_type: bool = True,
    preconditions: bool = True,
    postconditions: bool = True,
) -> Class: ...


def check_contracts(
    func_or_class: Union[Class, FunctionType] = None,
    *,
    module_names: Optional[set[str]] = None,
    argument_types: bool = True,
    return_type: bool = True,
    preconditions: bool = True,
    postconditions: bool = True,
) -> Union[Class, FunctionType]:
    """A decorator to enable contract checking for a function or class.

    When used with a class, all methods defined within the class have contract checking enabled.
    If module_names is not None, only functions or classes defined in a module whose name is in module_names are checked.

    When used with functions, `check_contracts` accepts four optional boolean keyword arguments to selectively disable checks when set to `False`:

    - `argument_types`: check parameter type annotations
    - `return_type`: check the return type annotation
    - `preconditions`: check preconditions
    - `postconditions`: check postconditions

    By default, all four checks are enabled. These arguments only affect functions, and are ignored when `check_contracts` is applied to a class.

    Example:
        >>> from python_ta.contracts import check_contracts
        >>> @check_contracts
        ... def divide(x: int, y: int) -> int:
        ...     \"\"\"Return x // y.
        ...
        ...     Preconditions:
        ...        - y != 0
        ...     \"\"\"
        ...     return x // y
    """

    @wrapt.decorator
    def _enable_function_contracts(wrapped, instance, args, kwargs):
        """A decorator that enables checking contracts for a function."""
        try:
            if instance is not None and inspect.isclass(instance):
                # This is a class method, so there is no instance.
                return _check_function_contracts(
                    wrapped,
                    None,
                    args,
                    kwargs,
                    argument_types_enabled=argument_types,
                    return_type_enabled=return_type,
                    preconditions_enabled=preconditions,
                    postconditions_enabled=postconditions,
                )
            else:
                return _check_function_contracts(
                    wrapped,
                    instance,
                    args,
                    kwargs,
                    argument_types_enabled=argument_types,
                    return_type_enabled=return_type,
                    preconditions_enabled=preconditions,
                    postconditions_enabled=postconditions,
                )
        except PyTAContractError as e:
            raise AssertionError(str(e)) from None

    # Optional Arguments passed to the decorator
    if func_or_class is None:
        return wrapt.PartialCallableObjectProxy(
            check_contracts,
            module_names=module_names,
            argument_types=argument_types,
            return_type=return_type,
            preconditions=preconditions,
            postconditions=postconditions,
        )

    if not ENABLE_CONTRACT_CHECKING:
        return func_or_class

    if module_names is not None and func_or_class.__module__ not in module_names:
        _debug(
            f"Warning: skipping contract check for {func_or_class.__name__} defined in {func_or_class.__module__} because module is not included as an argument."
        )
        return func_or_class
    elif inspect.isroutine(func_or_class):
        return _enable_function_contracts(func_or_class)
    elif inspect.isclass(func_or_class):
        add_class_invariants(func_or_class)
        return func_or_class
    else:
        # Default action
        return func_or_class


def add_class_invariants(klass: type) -> None:
    """Modify the given class to check representation invariants and method contracts."""
    if not ENABLE_CONTRACT_CHECKING or "__representation_invariants__" in klass.__dict__:
        # This means the class has already been decorated
        return

    _set_invariants(klass)

    klass_mod = _get_module(klass)
    cls_annotations = None  # This is a cached value set the first time new_setattr is called

    def new_setattr(self: klass, name: str, value: Any) -> None:
        """Set the value of the given attribute on self to the given value.

        Check representation invariants for this class when not within an instance method of the class.
        """
        if not ENABLE_CONTRACT_CHECKING:
            super(klass, self).__setattr__(name, value)
            return

        nonlocal cls_annotations
        if cls_annotations is None:
            cls_annotations = typing.get_type_hints(klass, localns=klass_mod.__dict__)

        if name in cls_annotations:
            try:
                _debug(f"Checking type of attribute {attr} for {klass.__qualname__} instance")
                check_type(
                    value,
                    cls_annotations[name],
                    collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS,
                )
            except TypeCheckError:
                raise AssertionError(
                    f"Value {_display_value(value)} for attribute {name} did not match expected type "
                    f"{_display_annotation(cls_annotations[name])}"
                ) from None
        original_attr_value_exists = False
        original_attr_value = None
        if hasattr(self, name):
            original_attr_value_exists = True
            original_attr_value = super(klass, self).__getattribute__(name)
        super(klass, self).__setattr__(name, value)
        frame_locals = inspect.currentframe().f_back.f_locals
        caller_self = frame_locals.get("self")
        if not isinstance(caller_self, type(self)):
            # Only validating if the attribute is not being set in a instance/class method
            # AND caller_self is an instance of self's type
            if klass_mod is not None:
                try:
                    _check_invariants(self, klass, klass_mod.__dict__)
                except PyTAContractError as e:
                    if original_attr_value_exists:
                        super(klass, self).__setattr__(name, original_attr_value)
                    else:
                        super(klass, self).__delattr__(name)
                    raise AssertionError(str(e)) from None
        elif caller_self is not self:
            # Keep track of mutations to instances that are of the same type as caller_self (and are also not `self`)
            # to enforce RIs on them only after the caller function returns.
            caller_klass = type(caller_self)
            if hasattr(caller_klass, "__mutated_instances__"):
                mutated_instances = getattr(caller_klass, "__mutated_instances__")
                if self not in mutated_instances:
                    mutated_instances.append(self)

    for attr, value in klass.__dict__.items():
        if inspect.isroutine(value):
            if isinstance(value, (staticmethod, classmethod)):
                # Don't check rep invariants for staticmethod and classmethod
                setattr(klass, attr, check_contracts(value))
            else:
                setattr(klass, attr, _instance_method_wrapper(value, klass))

    klass.__setattr__ = new_setattr


def _check_function_contracts(
    wrapped,
    instance,
    args,
    kwargs,
    argument_types_enabled: bool = True,
    return_type_enabled: bool = True,
    preconditions_enabled: bool = True,
    postconditions_enabled: bool = True,
):
    params = wrapped.__code__.co_varnames[: wrapped.__code__.co_argcount]
    if instance is not None:
        klass_mod = _get_module(type(instance))
        annotations = typing.get_type_hints(wrapped, globalns=klass_mod.__dict__)
    else:
        annotations = typing.get_type_hints(wrapped)
    args_with_self = args if instance is None else (instance,) + args

    if argument_types_enabled:
        # Check function parameter types
        for arg, param in zip(args_with_self, params):
            if param in annotations:
                try:
                    _debug(f"Checking type of parameter {param} in call to {wrapped.__qualname__}")
                    if STRICT_NUMERIC_TYPES:
                        check_type_strict(param, arg, annotations[param])
                    else:
                        check_type(arg, annotations[param])
                except (TypeError, TypeCheckError):
                    additional_suggestions = _get_argument_suggestions(arg, annotations[param])

                    raise PyTAContractError(
                        f"Argument value {_display_value(arg)} for {wrapped.__name__} parameter {param} "
                        f"did not match expected type {_display_annotation(annotations[param])}"
                        + (f"\n{additional_suggestions}" if additional_suggestions else "")
                    )

    function_locals = dict(zip(params, args_with_self))

    # Check bounded function
    if hasattr(wrapped, "__self__"):
        target = wrapped.__func__
    else:
        target = wrapped

    # Check function preconditions
    if not hasattr(target, "__preconditions__") and preconditions_enabled:
        target.__preconditions__: list[tuple[str, CodeType]] = []
        preconditions = parse_assertions(wrapped)
        for precondition in preconditions:
            try:
                compiled = compile(precondition, "<string>", "eval")
            except:
                _debug(
                    f"Warning: precondition {precondition} could not be parsed as a valid Python expression"
                )
                continue
            target.__preconditions__.append((precondition, compiled))

    if ENABLE_CONTRACT_CHECKING and preconditions_enabled:
        _check_assertions(wrapped, function_locals)

    # Check return type
    r = wrapped(*args, **kwargs)
    if return_type_enabled and "return" in annotations:
        return_type = annotations["return"]
        try:
            _debug(f"Checking return type from call to {wrapped.__qualname__}")
            if STRICT_NUMERIC_TYPES:
                check_type_strict("return", r, return_type)
            else:
                check_type(r, return_type)
        except (TypeError, TypeCheckError):
            raise PyTAContractError(
                f"Return value {_display_value(r)} for {wrapped.__name__} did not match "
                f"expected type {_display_annotation(return_type)}"
            )

    # Check function postconditions
    if postconditions_enabled and not hasattr(target, "__postconditions__"):
        target.__postconditions__: list[tuple[str, CodeType, str]] = []
        return_val_var_name = _get_legal_return_val_var_name(
            {**wrapped.__globals__, **function_locals}
        )
        postconditions = parse_assertions(wrapped, parse_token="Postcondition")
        for postcondition in postconditions:
            assertion = _replace_return_val_assertion(postcondition, return_val_var_name)
            try:
                compiled = compile(assertion, "<string>", "eval")
            except:
                _debug(
                    f"Warning: postcondition {postcondition} could not be parsed as a valid Python expression"
                )
                continue
            target.__postconditions__.append((postcondition, compiled, return_val_var_name))

    if ENABLE_CONTRACT_CHECKING and postconditions_enabled:
        _check_assertions(
            wrapped,
            function_locals,
            function_return_val=r,
            condition_type="postcondition",
        )

    return r


def check_type_strict(argname: str, value: Any, expected_type: type) -> None:
    """Ensure that `value` matches ``expected_type`` with strict type checking.

    This function enforces strict type distinctions within the numeric hierarchy (bool, int, float,
    complex), ensuring that the type of value is exactly the same as expected_type.
    """
    if not ENABLE_CONTRACT_CHECKING:
        return
    try:
        _check_inner_type(argname, value, expected_type)
    except (TypeError, TypeCheckError):
        raise TypeError(f"type of {argname} must be {expected_type}; got {value} instead")


def _check_inner_type(argname: str, value: Any, expected_type: type) -> None:
    """Recursively checks if `value` matches `expected_type` for strict type validation, specifically supports checking
    collections (list[int], dicts[float]) and Union types (bool | int).
    """
    inner_types = get_args(expected_type)
    outer_type = get_origin(expected_type)
    if outer_type is None:
        if (
            (type(value) is bool and expected_type in {int, float, complex})
            or (type(value) is int and expected_type in {float, complex})
            or (type(value) is float and expected_type is complex)
        ):
            raise TypeError(
                f"type of {argname} must be {expected_type}; got {type(value).__name__} instead"
            )
        else:
            check_type(
                value, expected_type, collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS
            )
    elif outer_type is typing.Union:
        for inner_type in inner_types:
            try:
                _check_inner_type(argname, value, inner_type)
                return
            except (TypeError, TypeCheckError):
                pass
        raise TypeError(f"type of {argname} must be {expected_type}; got {value} instead")
    elif outer_type in {list, set}:
        if isinstance(value, outer_type):
            for item in value:
                _check_inner_type(argname, item, inner_types[0])
        else:
            raise TypeError(f"type of {argname} must be {expected_type}; got {value} instead")
    elif outer_type is dict:
        if isinstance(value, dict):
            for key, item in value.items():
                _check_inner_type(argname, key, inner_types[0])
                _check_inner_type(argname, item, inner_types[1])
        else:
            raise TypeError(f"type of {argname} must be {expected_type}; got {value} instead")
    elif outer_type is tuple:
        if isinstance(value, tuple) and len(inner_types) == 2 and inner_types[1] is Ellipsis:
            for item in value:
                _check_inner_type(argname, item, inner_types[0])
        elif isinstance(value, tuple) and len(value) == len(inner_types):
            for item, inner_type in zip(value, inner_types):
                _check_inner_type(argname, item, inner_type)
        else:
            raise TypeError(f"type of {argname} must be {expected_type}; got {value} instead")
    else:
        check_type(
            value, expected_type, collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS
        )


def _get_argument_suggestions(arg: Any, annotation: type) -> str:
    """Returns potential suggestions for the given arg and its annotation"""
    try:
        if isinstance(arg, type) and issubclass(arg, annotation):
            return "Did you mean {cls}(...) instead of {cls}?".format(cls=arg.__name__)
    except TypeError:
        pass

    return ""


def _instance_method_wrapper(wrapped: Callable, klass: type) -> Callable:
    @wrapt.decorator
    def wrapper(wrapped, instance, args, kwargs):
        # Create an accumulator to store the instances mutated across this function call.
        # Store and restore existing mutated instance lists in case the instance method
        # executes another instance method.
        instance_klass = type(instance)
        mutated_instances_to_restore = None
        if hasattr(instance_klass, "__mutated_instances__"):
            mutated_instances_to_restore = getattr(instance_klass, "__mutated_instances__")
        setattr(instance_klass, "__mutated_instances__", [])

        try:
            r = _check_function_contracts(wrapped, instance, args, kwargs)
            if _instance_init_in_callstack(instance):
                return r
            _check_class_type_annotations(klass, instance)
            klass_mod = _get_module(klass)
            if klass_mod is not None and ENABLE_CONTRACT_CHECKING:
                _check_invariants(instance, klass, klass_mod.__dict__)

                # Additionally check RI violations on PyTA-decorated instances that were mutated
                # across the function call.
                mutated_instances = getattr(instance_klass, "__mutated_instances__", [])
                for mutated_instance in mutated_instances:
                    # Mutated instances may be of parent class types so the invariants to check should also be
                    # for the parent class and not the child class.
                    mutated_instance_klass = type(mutated_instance)
                    mutated_instance_klass_mod = _get_module(mutated_instance_klass)
                    _check_invariants(
                        mutated_instance,
                        mutated_instance_klass,
                        mutated_instance_klass_mod.__dict__,
                    )
        except PyTAContractError as e:
            raise AssertionError(str(e)) from None
        else:
            return r
        finally:
            if mutated_instances_to_restore is None:
                delattr(instance_klass, "__mutated_instances__")
            else:
                setattr(instance_klass, "__mutated_instances__", mutated_instances_to_restore)

    return wrapper(wrapped)


def _instance_init_in_callstack(instance: Any) -> bool:
    """Return whether instance's init is part of the current callstack

    Note: due to the nature of the check, externally defined __init__ functions with
    'self' defined as the first parameter may pass this check.
    """
    frame = inspect.currentframe().f_back
    while frame:
        frame_context_name = inspect.getframeinfo(frame).function
        frame_context_self = frame.f_locals.get("self")
        frame_context_vars = frame.f_code.co_varnames
        if (
            frame_context_name == "__init__"
            and frame_context_self is instance
            and frame_context_vars[0] == "self"
        ):
            return True
        frame = frame.f_back
    return False


def _check_class_type_annotations(klass: type, instance: Any) -> None:
    """Check that the type annotations for the class still hold.

    Precondition:
        - isinstance(instance, klass)
    """
    klass_mod = _get_module(klass)
    cls_annotations = typing.get_type_hints(klass, localns=klass_mod.__dict__)

    for attr, annotation in cls_annotations.items():
        value = getattr(instance, attr)
        try:
            _debug(f"Checking type of attribute {attr} for {klass.__qualname__} instance")
            check_type(
                value, annotation, collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS
            )
        except TypeCheckError:
            raise AssertionError(
                f"Value {_display_value(value)} for attribute {attr} did not match expected type "
                f"{_display_annotation(annotation)}"
            )


def _check_invariants(instance, klass: type, global_scope: dict) -> None:
    """Check that the representation invariants for the instance are satisfied."""
    if hasattr(instance, "__pyta_currently_checking"):
        # If already checking invariants for this instance, skip to avoid infinite recursion
        return

    super(type(instance), instance).__setattr__("__pyta_currently_checking", True)

    rep_invariants = getattr(klass, "__representation_invariants__", set())

    try:
        for invariant, compiled in rep_invariants:
            try:
                _debug(
                    "Checking representation invariant for "
                    f"{instance.__class__.__qualname__}: {invariant}"
                )
                check = eval(compiled, {**global_scope, "self": instance})
            except AssertionError as e:
                raise AssertionError(str(e)) from None
            except NameError as e:
                # Get the missing name
                missing = getattr(e, "name", None)
                if missing is None:
                    # Failsafe for version 3.9
                    message = re.search(r"name '(.+?)' is not defined", str(e))
                    if message:
                        missing = message.group(1)

                # Check if missing name is an attribute
                if missing is not None and hasattr(instance, missing):
                    print(
                        f"[WARNING] Could not find variable `{missing}` when evaluating representation invariant. Did you mean `self.{missing}`?",
                        file=sys.stderr,
                    )
                else:
                    _debug(f"Warning: could not evaluate representation invariant: {invariant}")
            except:
                _debug(f"Warning: could not evaluate representation invariant: {invariant}")
            else:
                if not check:
                    curr_attributes = ", ".join(
                        f"{k}: {_display_value(v)}"
                        for k, v in vars(instance).items()
                        if k != "__pyta_currently_checking"
                    )

                    curr_attributes = "{" + curr_attributes + "}"

                    raise PyTAContractError(
                        f'{instance.__class__.__name__} representation invariant "{invariant}" was violated for'
                        f" instance attributes {curr_attributes}"
                    )

    finally:
        delattr(instance, "__pyta_currently_checking")


def _get_legal_return_val_var_name(var_dict: dict) -> str:
    """
    Add '_' to the end of __function_return_value__ until a variable name that has not been used for any other
    variable in the function's scope is created. This is used to refer to the function's return value when evaluating
    postconditions.
    """
    legal_var_name = "__function_return_value__"

    while legal_var_name in var_dict:
        legal_var_name += "_"

    return legal_var_name


def _replace_return_val_assertion(assertion: str, return_val_var_name: Optional[str]) -> str:
    """
    Replace FUNCTION_RETURN_VALUE in the assertion with the legal python variable name generated and return the new
    assertion. If FUNCTION_RETURN_VALUE does not appear in assertion, then simply return the original assertion.

    Precondition: If FUNCTION_RETURN_VALUE is in assertion, then return_val_var_name is not None
    """

    if FUNCTION_RETURN_VALUE in assertion:
        return assertion.replace(FUNCTION_RETURN_VALUE, return_val_var_name)
    return assertion


def _check_assertions(
    wrapped: Callable[..., Any],
    function_locals: dict,
    condition_type: str = "precondition",
    function_return_val: Any = None,
) -> None:
    """Check that the given assertions are still satisfied."""
    # Check bounded function
    if hasattr(wrapped, "__self__"):
        target = wrapped.__func__
    else:
        target = wrapped
    assertions = []
    if condition_type == "precondition":
        assertions = target.__preconditions__
    elif condition_type == "postcondition":
        assertions = target.__postconditions__
    for assertion_str, compiled, *return_val_var_name in assertions:
        return_val_dict = {}
        if condition_type == "postcondition":
            return_val_dict = {return_val_var_name[0]: function_return_val}
        try:
            _debug(f"Checking {condition_type} for {wrapped.__qualname__}: {assertion_str}")
            check = eval(compiled, {**wrapped.__globals__, **function_locals, **return_val_dict})
        except AssertionError as e:
            raise AssertionError(str(e)) from None
        except:
            _debug(f"Warning: could not evaluate {condition_type}: {assertion_str}")
        else:
            if not check:
                arg_string = ", ".join(
                    f"{k}: {_display_value(v)}" for k, v in function_locals.items()
                )
                arg_string = "{" + arg_string + "}"

                return_val_string = ""

                if condition_type == "postcondition":
                    return_val_string = f" and return value {function_return_val}"
                raise PyTAContractError(
                    f'{wrapped.__name__} {condition_type} "{assertion_str}" was '
                    f"violated for arguments {arg_string}{return_val_string}"
                )


def parse_assertions(obj: Any, parse_token: str = "Precondition") -> list[str]:
    """Return a list of preconditions/postconditions/representation invariants parsed from the given entity's docstring.

    Uses parse_token to determine what to look for. parse_token defaults to Precondition.

    Currently only supports two forms:

    1. A single line of the form "<parse_token>: <cond>"
    2. A group of lines starting with "<parse_token>s:", where each subsequent
       line is of the form "- <cond>". Each line is considered a separate condition.
       The lines can be separated by blank lines, but no other text.
    """
    if hasattr(obj, "doc_node") and obj.doc_node is not None:
        # Check if obj is an astroid node
        docstring = obj.doc_node.value
    else:
        docstring = getattr(obj, "__doc__") or ""
    lines = [line.strip() for line in docstring.split("\n")]
    assertion_lines = [
        i for i, line in enumerate(lines) if line.lower().startswith(parse_token.lower())
    ]

    if assertion_lines == []:
        return []

    first = assertion_lines[0]

    if lines[first].startswith(parse_token + ":"):
        return [lines[first][len(parse_token + ":") :].strip()]
    elif lines[first].startswith(parse_token + "s:"):
        assertions = []
        for line in lines[first + 1 :]:
            if line.startswith("-"):
                assertion = line[1:].strip()
                if hasattr(obj, "__qualname__"):
                    _debug(f"Adding assertion to {obj.__qualname__}: {assertion}")
                assertions.append(assertion)
            elif line != "":
                break
        return assertions
    else:
        return []


def _display_value(value: Any, max_length: int = _DEFAULT_MAX_VALUE_LENGTH) -> str:
    """Return a human-friendly representation of the given value.

    If DEBUG_CONTRACTS is False, truncate long strings to max_length characters.

    Preconditions:
        - max_length >= 5
    """
    s = repr(value)
    if not DEBUG_CONTRACTS and len(s) > max_length:
        i = (max_length - 3) // 2
        return s[:i] + "..." + s[-i:]
    else:
        return s


def _display_annotation(annotation: Any) -> str:
    """Return a human-friendly representation of the given type annotation.

    >>> _display_annotation(int)
    'int'
    >>> _display_annotation(list[int])
    'list[int]'
    >>> from typing import List
    >>> _display_annotation(List[int])
    'typing.List[int]'
    """
    if annotation is type(None):  # Use 'None' instead of 'NoneType'
        return "None"
    if hasattr(annotation, "__origin__"):  # Generic type annotations
        return repr(annotation)
    elif hasattr(annotation, "__name__"):
        return annotation.__name__
    else:
        return repr(annotation)


def _get_module(obj: Any) -> ModuleType:
    """Return the module where obj was defined (normally obj.__module__).

    NOTE: this function defines a special case when using PyCharm and the file
    defining the object is "Run in Python Console". In this case, the pydevd runner
    renames the '__main__' module to 'pydev_umd', and so we need to access that
    module instead. This behaviour can be disabled by setting RENAME_MAIN_TO_PYDEV_UMD
    to False.
    """
    module_name = obj.__module__
    module = sys.modules[module_name]

    if (
        module_name != "__main__"
        or not RENAME_MAIN_TO_PYDEV_UMD
        or _PYDEV_UMD_NAME not in sys.modules
    ):
        return module

    # Get a function/class name to check whether it is defined in the module
    if isinstance(obj, (FunctionType, type)):
        name = obj.__name__
    else:
        # For any other type of object, be conservative and just return the module
        return module

    if name in vars(module):
        return module
    else:
        return sys.modules[_PYDEV_UMD_NAME]


def _debug(msg: str) -> None:
    """Display a debugging message.

    Do nothing if DEBUG_CONTRACTS is False.
    """
    if not DEBUG_CONTRACTS:
        return
    logging.basicConfig(format="[%(levelname)s] %(message)s", level=logging.DEBUG)
    logging.debug(msg)


def _set_invariants(klass: type) -> None:
    """Retrieve and set the representation invariants of this class"""
    # Update representation invariants from this class' docstring and those of its superclasses.
    rep_invariants: list[tuple[str, CodeType]] = []

    # Iterate over all inherited classes except builtins
    for cls in reversed(klass.__mro__):
        if "__representation_invariants__" in cls.__dict__:
            rep_invariants.extend(cls.__representation_invariants__)
        elif cls.__module__ != "builtins":
            assertions = parse_assertions(cls, parse_token="Representation Invariant")
            # Try compiling assertions
            for assertion in assertions:
                try:
                    compiled = compile(assertion, "<string>", "eval")
                except:
                    _debug(
                        f"Warning: representation invariant {assertion} could not be parsed as a valid Python expression"
                    )
                    continue
                rep_invariants.append((assertion, compiled))

    setattr(klass, "__representation_invariants__", rep_invariants)


def validate_invariants(obj: object) -> None:
    """Check that the representation invariants of obj are satisfied."""
    klass = obj.__class__
    klass_mod = _get_module(klass)

    try:
        _check_invariants(obj, klass, klass_mod.__dict__)
    except PyTAContractError as e:
        raise AssertionError(str(e)) from None

pyta-uoft / pyta / 19686422763

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