_impl.py

# This file is part of Hypothesis, which may be found at
# https://github.com/HypothesisWorks/hypothesis/
#
# Copyright the Hypothesis Authors.
# Individual contributors are listed in AUTHORS.rst and the git log.
#
# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.

import sys
import unittest
from functools import partial
from typing import TYPE_CHECKING, Optional, Type, TypeVar, Union

from django import forms as df, test as dt
from django.contrib.staticfiles import testing as dst
from django.core.exceptions import ValidationError
from django.db import IntegrityError, models as dm

from hypothesis import reject, strategies as st
from hypothesis.errors import InvalidArgument
from hypothesis.extra.django._fields import from_field
from hypothesis.strategies._internal.utils import defines_strategy

if sys.version_info >= (3, 10):
    from types import EllipsisType as EllipsisType
elif TYPE_CHECKING:
    from builtins import ellipsis as EllipsisType
else:
    EllipsisType = type(Ellipsis)

ModelT = TypeVar("ModelT", bound=dm.Model)


class HypothesisTestCase:
    def setup_example(self):
        self._pre_setup()

    def teardown_example(self, example):
        self._post_teardown()

    def __call__(self, result=None):
        testMethod = getattr(self, self._testMethodName)
        if getattr(testMethod, "is_hypothesis_test", False):
            return unittest.TestCase.__call__(self, result)
        else:
            return dt.SimpleTestCase.__call__(self, result)


class TestCase(HypothesisTestCase, dt.TestCase):
    pass


class TransactionTestCase(HypothesisTestCase, dt.TransactionTestCase):
    pass


class LiveServerTestCase(HypothesisTestCase, dt.LiveServerTestCase):
    pass


class StaticLiveServerTestCase(HypothesisTestCase, dst.StaticLiveServerTestCase):
    pass


@defines_strategy()
def from_model(
    model: Type[ModelT], /, **field_strategies: Union[st.SearchStrategy, EllipsisType]
) -> st.SearchStrategy[ModelT]:
    """Return a strategy for examples of ``model``.

    .. warning::
        Hypothesis creates saved models. This will run inside your testing
        transaction when using the test runner, but if you use the dev console
        this will leave debris in your database.

    ``model`` must be an subclass of :class:`~django:django.db.models.Model`.
    Strategies for fields may be passed as keyword arguments, for example
    ``is_staff=st.just(False)``.  In order to support models with fields named
    "model", this is a positional-only parameter.

    Hypothesis can often infer a strategy based the field type and validators,
    and will attempt to do so for any required fields.  No strategy will be
    inferred for an :class:`~django:django.db.models.AutoField`, nullable field,
    foreign key, or field for which a keyword
    argument is passed to ``from_model()``.  For example,
    a Shop type with a foreign key to Company could be generated with::

        shop_strategy = from_model(Shop, company=from_model(Company))

    Like for :func:`~hypothesis.strategies.builds`, you can pass
    ``...`` (:obj:`python:Ellipsis`) as a keyword argument to infer a strategy for
    a field which has a default value instead of using the default.
    """
    if not issubclass(model, dm.Model):
        raise InvalidArgument(f"{model=} must be a subtype of Model")

    fields_by_name = {f.name: f for f in model._meta.concrete_fields}
    for name, value in sorted(field_strategies.items()):
        if value is ...:
            field_strategies[name] = from_field(fields_by_name[name])
    for name, field in sorted(fields_by_name.items()):
        if (
            name not in field_strategies
            and not field.auto_created
            and field.default is dm.fields.NOT_PROVIDED
        ):
            field_strategies[name] = from_field(field)

    for field in field_strategies:
        if model._meta.get_field(field).primary_key:
            # The primary key is generated as part of the strategy. We
            # want to find any existing row with this primary key and
            # overwrite its contents.
            kwargs = {field: field_strategies.pop(field)}
            kwargs["defaults"] = st.fixed_dictionaries(field_strategies)  # type: ignore
            return _models_impl(st.builds(model.objects.update_or_create, **kwargs))

    # The primary key is not generated as part of the strategy, so we
    # just match against any row that has the same value for all
    # fields.
    return _models_impl(st.builds(model.objects.get_or_create, **field_strategies))


@st.composite
def _models_impl(draw, strat):
    """Handle the nasty part of drawing a value for models()"""
    try:
        return draw(strat)[0]
    except IntegrityError:
        reject()


@defines_strategy()
def from_form(
    form: Type[df.Form],
    form_kwargs: Optional[dict] = None,
    **field_strategies: Union[st.SearchStrategy, EllipsisType],
) -> st.SearchStrategy[df.Form]:
    """Return a strategy for examples of ``form``.

    ``form`` must be an subclass of :class:`~django:django.forms.Form`.
    Strategies for fields may be passed as keyword arguments, for example
    ``is_staff=st.just(False)``.

    Hypothesis can often infer a strategy based the field type and validators,
    and will attempt to do so for any required fields.  No strategy will be
    inferred for a disabled field or field for which a keyword argument
    is passed to ``from_form()``.

    This function uses the fields of an unbound ``form`` instance to determine
    field strategies, any keyword arguments needed to instantiate the unbound
    ``form`` instance can be passed into ``from_form()`` as a dict with the
    keyword ``form_kwargs``. E.g.::

        shop_strategy = from_form(Shop, form_kwargs={"company_id": 5})

    Like for :func:`~hypothesis.strategies.builds`, you can pass
    ``...`` (:obj:`python:Ellipsis`) as a keyword argument to infer a strategy for
    a field which has a default value instead of using the default.
    """
    # currently unsupported:
    # ComboField
    # FilePathField
    # FileField
    # ImageField
    form_kwargs = form_kwargs or {}
    if not issubclass(form, df.BaseForm):
        raise InvalidArgument(f"{form=} must be a subtype of Form")

    # Forms are a little bit different from models. Model classes have
    # all their fields defined, whereas forms may have different fields
    # per-instance. So, we ought to instantiate the form and get the
    # fields from the instance, thus we need to accept the kwargs for
    # instantiation as well as the explicitly defined strategies

    unbound_form = form(**form_kwargs)
    fields_by_name = {}
    for name, field in unbound_form.fields.items():
        if isinstance(field, df.MultiValueField):
            # PS: So this is a little strange, but MultiValueFields must
            # have their form data encoded in a particular way for the
            # values to actually be picked up by the widget instances'
            # ``value_from_datadict``.
            # E.g. if a MultiValueField named 'mv_field' has 3
            # sub-fields then the ``value_from_datadict`` will look for
            # 'mv_field_0', 'mv_field_1', and 'mv_field_2'. Here I'm
            # decomposing the individual sub-fields into the names that
            # the form validation process expects
            for i, _field in enumerate(field.fields):
                fields_by_name[f"{name}_{i}"] = _field
        else:
            fields_by_name[name] = field
    for name, value in sorted(field_strategies.items()):
        if value is ...:
            field_strategies[name] = from_field(fields_by_name[name])

    for name, field in sorted(fields_by_name.items()):
        if name not in field_strategies and not field.disabled:
            field_strategies[name] = from_field(field)

    return _forms_impl(
        st.builds(
            partial(form, **form_kwargs),
            data=st.fixed_dictionaries(field_strategies),  # type: ignore
        )
    )


@st.composite
def _forms_impl(draw, strat):
    """Handle the nasty part of drawing a value for from_form()"""
    try:
        return draw(strat)
    except ValidationError:
        reject()