Fixtures in case files can now be automatically imported using the **experimental** @parametrize_with_cases(import_fixtures=True). Fixes #193

Also, Fixed an issue where a case transformed into a fixture, with the same name as the fixture it requires, would lead to a `pytest` fixture recursion.

Author: Sylvain MARIE

docs/api_reference.md

@@ -246,7 +246,8 @@ CaseFilter(filter_function: Callable)
                         filter: Callable = None,
                         ids: Union[Callable, Iterable[str]] = None,
                         idstyle: Union[str, Callable] = None,
-                        scope: str = "function"
+                        scope: str = "function",
+                        import_fixtures: bool = False
                         )
 ```
 
@@ -287,6 +288,7 @@ argvalues = get_parametrize_args(host_class_or_module_of_f, cases_funs)
 
  - `scope`: The scope of the union fixture to create if `fixture_ref`s are found in the argvalues
 
+ - `import_fixtures`: experimental feature. Turn this to `True` in order to automatically import all fixtures defined in the cases module into the current module.
 
 ### `get_current_case_id`
 

docs/index.md

@@ -370,7 +370,11 @@ test_generators.py::test_foo[simple_generator-who=there] PASSED [100%]
 
 #### Cases requiring fixtures
 
-Cases can use fixtures the same way as [test functions do](https://docs.pytest.org/en/stable/fixture.html#fixtures-as-function-arguments): simply add the fixture names as arguments in their signature and make sure the fixture exists either in the same module, or in a [`conftest.py`](https://docs.pytest.org/en/stable/fixture.html?highlight=conftest.py#conftest-py-sharing-fixture-functions) file in one of the parent packages. See [`pytest` documentation on sharing fixtures](https://docs.pytest.org/en/stable/fixture.html?highlight=conftest.py#conftest-py-sharing-fixture-functions).
+Cases can use fixtures the same way as [test functions do](https://docs.pytest.org/en/stable/fixture.html#fixtures-as-function-arguments): simply add the fixture names as arguments in their signature and make sure the fixture exists or is imported either in the module where `@parametrize_with_cases` is used, or in a [`conftest.py`](https://docs.pytest.org/en/stable/fixture.html?highlight=conftest.py#conftest-py-sharing-fixture-functions) file in one of the parent packages. 
+
+See [`pytest` documentation on sharing fixtures](https://docs.pytest.org/en/stable/fixture.html?highlight=conftest.py#conftest-py-sharing-fixture-functions)and this [blog](https://gist.github.com/peterhurford/09f7dcda0ab04b95c026c60fa49c2a68).
+
+You can use the **experimental** `@parametrize_with_cases(import_fixtures=True)` argument to perform the import automatically for you, see [API reference](./api_reference.md#parametrize_with_cases).
 
 !!! warning "Use `@fixture` instead of `@pytest.fixture`"
     If a fixture is used by *some* of your cases only, then you *should* use the `@fixture` decorator from pytest-cases instead of the standard `@pytest.fixture`. Otherwise you fixture will be setup/teardown for all cases even those not requiring it. See [`@fixture` doc](./api_reference.md#fixture).

pytest_cases/case_parametrizer_new.py

@@ -7,7 +7,7 @@
 
 import functools
 from importlib import import_module
-from inspect import getmembers, isfunction, ismethod
+from inspect import getmembers, ismodule
 import re
 from warnings import warn
 
@@ -17,11 +17,13 @@
     pass
 
 from .common_mini_six import string_types
-from .common_others import get_code_first_line, AUTO, qname, funcopy, needs_binding
+from .common_others import get_code_first_line, AUTO, qname, funcopy, needs_binding, get_function_host, \
+    in_same_module, get_host_module
 from .common_pytest_marks import copy_pytest_marks, make_marked_parameter_value, remove_pytest_mark, filter_marks, \
     get_param_argnames_as_list
 from .common_pytest_lazy_values import lazy_value, LazyTupleItem
-from .common_pytest import safe_isclass, MiniMetafunc, is_fixture, get_fixture_name, inject_host, add_fixture_params
+from .common_pytest import safe_isclass, MiniMetafunc, is_fixture, get_fixture_name, inject_host, add_fixture_params, \
+    list_all_fixtures_in
 
 from . import fixture
 from .case_funcs import matches_tag_query, is_case_function, is_case_class, CASE_PREFIX_FUN, copy_case_info, \
@@ -62,7 +64,8 @@ def parametrize_with_cases(argnames,                # type: Union[str, List[str]
                            idstyle=None,            # type: Union[str, Callable]
                            # idgen=_IDGEN,            # type: Union[str, Callable]
                            debug=False,             # type: bool
-                           scope="function"         # type: str
+                           scope="function",        # type: str
+                           import_fixtures=False    # type: bool
                            ):
     # type: (...) -> Callable[[Callable], Callable]
     """
@@ -116,6 +119,8 @@ def parametrize_with_cases(argnames,                # type: Union[str, List[str]
         transformed into fixtures. As opposed to `ids`, a callable provided here will receive a `ParamAlternative`
         object indicating which generated fixture should be used. See `@parametrize` for details.
     :param scope: the scope of the union fixture to create if `fixture_ref`s are found in the argvalues
+    :param import_fixtures: experimental feature. Turn this to True in order to automatically import all fixtures
+        defined in the cases module into the current module.
     :param debug: a boolean flag to debug what happens behind the scenes
     :return:
     """
@@ -139,7 +144,8 @@ def _apply_parametrization(f, host_class_or_module):
         # Transform the various case functions found into `lazy_value` (for case functions not requiring fixtures)
         # or `fixture_ref` (for case functions requiring fixtures - for them we create associated case fixtures in
         # `host_class_or_module`)
-        argvalues = get_parametrize_args(host_class_or_module, cases_funs, prefix=prefix, debug=debug, scope=scope)
+        argvalues = get_parametrize_args(host_class_or_module, cases_funs, prefix=prefix,
+                                         import_fixtures=import_fixtures, debug=debug, scope=scope)
 
         # Finally apply parametrization - note that we need to call the private method so that fixture are created in
         # the right module (not here)
@@ -289,6 +295,7 @@ def get_parametrize_args(host_class_or_module,    # type: Union[Type, ModuleType
                          cases_funs,              # type: List[Callable]
                          prefix,                  # type: str
                          scope="function",        # type: str
+                         import_fixtures=False,   # type: bool
                          debug=False              # type: bool
                          ):
     # type: (...) -> List[Union[lazy_value, fixture_ref]]
@@ -304,16 +311,22 @@ def get_parametrize_args(host_class_or_module,    # type: Union[Type, ModuleType
 
     :param host_class_or_module: host of the parametrization target. A class or a module.
     :param cases_funs: a list of case functions, returned typically by `get_all_cases`
+    :param prefix:
+    :param scope:
+    :param import_fixtures: experimental feature. Turn this to True in order to automatically import all fixtures
+        defined in the cases module into the current module.
     :param debug: a boolean flag, turn it to True to print debug messages.
     :return:
     """
-    return [c for _f in cases_funs for c in case_to_argvalues(host_class_or_module, _f, prefix, scope, debug)]
+    return [c for _f in cases_funs for c in case_to_argvalues(host_class_or_module, _f, prefix, scope, import_fixtures,
+                                                              debug)]
 
 
 def case_to_argvalues(host_class_or_module,    # type: Union[Type, ModuleType]
                       case_fun,                # type: Callable
                       prefix,                  # type: str
                       scope,                   # type: str
+                      import_fixtures=False,   # type: bool
                       debug=False              # type: bool
                       ):
     # type: (...) -> Tuple[lazy_value]
@@ -328,6 +341,8 @@ def case_to_argvalues(host_class_or_module,    # type: Union[Type, ModuleType]
     Otherwise, `case_fun` represents a single case: in that case a single `lazy_value` is returned.
 
     :param case_fun:
+    :param import_fixtures: experimental feature. Turn this to True in order to automatically import all fixtures
+        defined in the cases module into the current module.
     :return:
     """
     # get the id from the case function either added by the @case decorator, or default one.
@@ -371,7 +386,8 @@ def case_to_argvalues(host_class_or_module,    # type: Union[Type, ModuleType]
 
         # create or reuse a fixture in the host (pytest collector: module or class) of the parametrization target
         fix_name, remaining_marks = get_or_create_case_fixture(case_id, case_fun, host_class_or_module,
-                                                               meta.fixturenames_not_in_sig, scope, debug)
+                                                               meta.fixturenames_not_in_sig, scope,
+                                                               import_fixtures=import_fixtures, debug=debug)
 
         # reference that case fixture, and preserve the case id in the associated id whatever the generated fixture name
         argvalues = fixture_ref(fix_name, id=case_id)
@@ -387,6 +403,7 @@ def get_or_create_case_fixture(case_id,                # type: str
                                target_host,            # type: Union[Type, ModuleType]
                                add_required_fixtures,  # type: Iterable[str]
                                scope,                  # type: str
+                               import_fixtures=False,  # type: bool
                                debug=False             # type: bool
                                ):
     # type: (...) -> Tuple[str, Tuple[MarkInfo]]
@@ -407,6 +424,8 @@ def get_or_create_case_fixture(case_id,                # type: str
     :param case_fun:
     :param target_host:
     :param add_required_fixtures:
+    :param import_fixtures: experimental feature. Turn this to True in order to automatically import all fixtures
+        defined in the cases module into the current module.
     :param debug:
     :return: the newly created fixture name, and the remaining marks not applied
     """
@@ -417,15 +436,15 @@ def get_or_create_case_fixture(case_id,                # type: str
 
     # source: detect a functools.partial wrapper created by us because of a host class
     true_case_func, case_in_class = _get_original_case_func(case_fun)
-    # case_host = case_fun.host_class if case_in_class else import_module(case_fun.__module__)
+    true_case_func_host = get_function_host(true_case_func)
 
     # for checks
     orig_name = true_case_func.__name__
     orig_case = true_case_func
 
     # destination
     target_in_class = safe_isclass(target_host)
-    fix_cases_dct = _get_fixture_cases(target_host)  # get our "storage unit" in this module
+    fix_cases_dct, imported_fixtures_list = _get_fixture_cases(target_host)  # get our "storage unit" in this module
 
     # shortcut if the case fixture is already known/registered in target host
     try:
@@ -439,9 +458,29 @@ def get_or_create_case_fixture(case_id,                # type: str
     # not yet known there. Create a new symbol in the target host :
     # we need a "free" fixture name, and a "free" symbol name
     existing_fixture_names = []
-    for n, symb in getmembers(target_host, lambda f: isfunction(f) or ismethod(f)):
-        if is_fixture(symb):
-            existing_fixture_names.append(get_fixture_name(symb))
+    # -- fixtures in target module or class should not be overridden
+    existing_fixture_names += list_all_fixtures_in(target_host, recurse_to_module=False)
+    # -- are there fixtures in source module or class ? should not be overridden too
+    if not in_same_module(target_host, true_case_func_host):
+        fixtures_in_cases_module = list_all_fixtures_in(true_case_func_host, recurse_to_module=False)
+        if len(fixtures_in_cases_module) > 0:
+            # EXPERIMENTAL we can try to import the fixtures into current module
+            if import_fixtures:
+                from_module = get_host_module(true_case_func_host)
+                if from_module not in imported_fixtures_list:
+                    for f in list_all_fixtures_in(true_case_func_host, recurse_to_module=False, return_names=False):
+                        f_name = get_fixture_name(f)
+                        if (f_name in existing_fixture_names) or (f.__name__ in existing_fixture_names):
+                            raise ValueError("Cannot import fixture %r from %r as it would override an existing symbol in "
+                                             "%r. Please set `@parametrize_with_cases(import_fixtures=False)`"
+                                             "" % (f, from_module, target_host))
+                        target_host_module = target_host if not target_in_class else get_host_module(target_host)
+                        setattr(target_host_module, f.__name__, f)
+
+                    imported_fixtures_list.append(from_module)
+
+            # Fix the problem with  "case_foo(foo)" leading to the generated fixture having the same name
+            existing_fixture_names += fixtures_in_cases_module
 
     def name_changer(name, i):
         return name + '_' * i
@@ -499,18 +538,35 @@ def name_changer(name, i):
     return fix_name, case_marks
 
 
-def _get_fixture_cases(module  # type: ModuleType
+def _get_fixture_cases(module_or_class  # type: Union[ModuleType, Type]
                        ):
     """
-    Returns our 'storage unit' in a module, used to remember the fixtures created from case functions.
+    Returns our 'storage unit' in a module or class, used to remember the fixtures created from case functions.
     That way we can reuse fixtures already created for cases, in a given module/class.
+
+    In addition, the host module of the class, or the module itself, is used to store a list of modules
+    from where we imported fixtures already. This relates to the EXPERIMENTAL `import_fixtures=True` param.
     """
-    try:
-        cache = module._fixture_cases
-    except AttributeError:
-        cache = dict()
-        module._fixture_cases = cache
-    return cache
+    if ismodule(module_or_class):
+        # module: everything is stored in the same place
+        try:
+            cache, imported_fixtures_list = module_or_class._fixture_cases
+        except AttributeError:
+            cache = dict()
+            imported_fixtures_list = []
+            module_or_class._fixture_cases = (cache, imported_fixtures_list)
+    else:
+        # class: on class only the fixtures dict is stored
+        try:
+            cache = module_or_class._fixture_cases
+        except AttributeError:
+            cache = dict()
+            module_or_class._fixture_cases = cache
+
+        # grab the imported fixtures list from the module host
+        _, imported_fixtures_list = _get_fixture_cases(get_host_module(module_or_class))
+
+    return cache, imported_fixtures_list
 
 
 def import_default_cases_module(f):

pytest_cases/common_others.py

@@ -211,6 +211,19 @@ def __exit__(self, exc_type, exc_val, exc_tb):
 """Marker for automatic defaults"""
 
 
+def get_host_module(a):
+    """get the host module of a, or a if it is already a module"""
+    if inspect.ismodule(a):
+        return a
+    else:
+        return import_module(a.__module__)
+
+
+def in_same_module(a, b):
+    """Compare the host modules of a and b"""
+    return get_host_module(a) == get_host_module(b)
+
+
 def get_function_host(func, fallback_to_module=True):
     """
     Returns the module or class where func is defined. Approximate method based on qname but "good enough"
@@ -228,8 +241,7 @@ def get_function_host(func, fallback_to_module=True):
             raise
 
     if host is None:
-        host = import_module(func.__module__)
-        # assert func in host
+        host = get_host_module(func)
 
     return host
 

pytest_cases/common_pytest.py

@@ -4,7 +4,9 @@
 # License: 3-clause BSD, <https://github.com/smarie/python-pytest-cases/blob/master/LICENSE>
 from __future__ import division
 
+import inspect
 import sys
+from importlib import import_module
 
 from makefun import add_signature_parameters, wraps
 
@@ -86,6 +88,31 @@ def is_fixture(fixture_fun  # type: Any
         return False
 
 
+def list_all_fixtures_in(cls_or_module, return_names=True, recurse_to_module=False):
+    """
+    Returns a list containing all fixture names (or symbols if `return_names=False`)
+    in the given class or module.
+
+    Note that `recurse_to_module` can be used so that the fixtures in the parent
+    module of a class are listed too.
+
+    :param cls_or_module:
+    :param return_names:
+    :param recurse_to_module:
+    :return:
+    """
+    res = [get_fixture_name(symb) if return_names else symb
+           for n, symb in inspect.getmembers(cls_or_module, lambda f: inspect.isfunction(f) or inspect.ismethod(f))
+           if is_fixture(symb)]
+
+    if recurse_to_module and not inspect.ismodule(cls_or_module):
+        # TODO currently this only works for a single level of nesting, we should use __qualname__ (py3) or .im_class
+        host = import_module(cls_or_module.__module__)
+        res += list_all_fixtures_in(host, recurse_to_module=True, return_names=return_names)
+
+    return res
+
+
 def safe_isclass(obj  # type: object
                  ):
     # type: (...) -> bool

pytest_cases/tests/cases/issues/test_issue_193.py

@@ -0,0 +1,24 @@
+import pytest_cases
+
+
+from .test_issue_193_cases import case_two_positive_ints, case_two_positive_ints2
+
+
+@pytest_cases.parametrize_with_cases("x", cases=case_two_positive_ints, debug=True, import_fixtures=True)
+def test_bar(x):
+    assert x is not None
+
+
+@pytest_cases.parametrize_with_cases("x", cases=case_two_positive_ints2, debug=True, import_fixtures=True)
+def test_bar(x):
+    assert x is not None
+
+
+@pytest_cases.parametrize_with_cases("x", debug=True, import_fixtures=True)
+def test_foo(x):
+    assert x is not None
+
+
+@pytest_cases.parametrize_with_cases("x", debug=True, import_fixtures=True)
+def test_bar(x):
+    assert x is not None

pytest_cases/tests/cases/issues/test_issue_193_bis.py

@@ -0,0 +1,15 @@
+# We make sure that two files requiring the same cases files and importing fixtures can work concurrently
+import pytest_cases
+
+
+from .test_issue_193_cases import case_two_positive_ints, case_two_positive_ints2
+
+
+@pytest_cases.parametrize_with_cases("x", cases=case_two_positive_ints, debug=True, import_fixtures=True)
+def test_bar(x):
+    assert x is not None
+
+
+@pytest_cases.parametrize_with_cases("x", cases=case_two_positive_ints2, debug=True, import_fixtures=True)
+def test_bar(x):
+    assert x is not None

pytest_cases/tests/cases/issues/test_issue_193_cases.py

@@ -0,0 +1,16 @@
+import pytest_cases
+
+
+@pytest_cases.fixture
+def two_positive_ints():
+    return 1, 2
+
+
+def case_two_positive_ints(two_positive_ints):
+    """ Inputs are two positive integers """
+    return two_positive_ints
+
+
+def case_two_positive_ints2(two_positive_ints):
+    """ Inputs are two positive integers """
+    return two_positive_ints