Implement facade for pytest parametrize, fixtures, classlevel

Add factilities to implement pytest.mark.parametrize and
pytest.fixtures patterns, which largely resemble things we are
already doing.

Ensure a facade is used, so that the test suite remains independent
of py.test, but also tailors the functions to the more limited
scope in which we are using them.

Additionally, create a class-based version that works from the
same facade.

Several old polymorphic tests as well as two of the sql test
are refactored to use the new features.

Change-Id: I6ef8af1dafff92534313016944d447f9439856cf
References: #4896

2 files changed, 185 insertions, 16 deletions

diff --git a/lib/sqlalchemy/testing/plugin/plugin_base.py b/lib/sqlalchemy/testing/plugin/plugin_base.py
index 859d1d779..a2f969a66 100644
--- a/lib/sqlalchemy/testing/plugin/plugin_base.py
+++ b/lib/sqlalchemy/testing/plugin/plugin_base.py
@@ -16,6 +16,7 @@ is py.test.
 
 from __future__ import absolute_import
 
+import abc
 import re
 import sys
 
@@ -24,8 +25,15 @@ py3k = sys.version_info >= (3, 0)
 
 if py3k:
     import configparser
+
+    ABC = abc.ABC
 else:
     import ConfigParser as configparser
+    import collections as collections_abc  # noqa
+
+    class ABC(object):
+        __metaclass__ = abc.ABCMeta
+
 
 # late imports
 fixtures = None
@@ -238,14 +246,6 @@ def set_coverage_flag(value):
     options.has_coverage = value
 
 
-_skip_test_exception = None
-
-
-def set_skip_test(exc):
-    global _skip_test_exception
-    _skip_test_exception = exc
-
-
 def post_begin():
     """things to set up later, once we know coverage is running."""
     # Lazy setup of other options (post coverage)
@@ -331,10 +331,10 @@ def _monkeypatch_cdecimal(options, file_config):
 
 
 @post
-def _init_skiptest(options, file_config):
+def _init_symbols(options, file_config):
     from sqlalchemy.testing import config
 
-    config._skip_test_exception = _skip_test_exception
+    config._fixture_functions = _fixture_fn_class()
 
 
 @post
@@ -486,10 +486,10 @@ def _setup_profiling(options, file_config):
     )
 
 
-def want_class(cls):
+def want_class(name, cls):
     if not issubclass(cls, fixtures.TestBase):
         return False
-    elif cls.__name__.startswith("_"):
+    elif name.startswith("_"):
         return False
     elif (
         config.options.backend_only
@@ -711,3 +711,29 @@ def _do_skips(cls):
 
 def _setup_config(config_obj, ctx):
     config._current.push(config_obj, testing)
+
+
+class FixtureFunctions(ABC):
+    @abc.abstractmethod
+    def skip_test_exception(self, *arg, **kw):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def combinations(self, *args, **kw):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def param_ident(self, *args, **kw):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def fixture(self, fn):
+        raise NotImplementedError()
+
+
+_fixture_fn_class = None
+
+
+def set_fixture_functions(fixture_fn_class):
+    global _fixture_fn_class
+    _fixture_fn_class = fixture_fn_class
diff --git a/lib/sqlalchemy/testing/plugin/pytestplugin.py b/lib/sqlalchemy/testing/plugin/pytestplugin.py
index e0335c135..5d91db5d7 100644
--- a/lib/sqlalchemy/testing/plugin/pytestplugin.py
+++ b/lib/sqlalchemy/testing/plugin/pytestplugin.py
@@ -8,7 +8,11 @@ except ImportError:
 import argparse
 import collections
 import inspect
+import itertools
+import operator
 import os
+import re
+import sys
 
 import pytest
 
@@ -87,7 +91,7 @@ def pytest_configure(config):
         bool(getattr(config.option, "cov_source", False))
     )
 
-    plugin_base.set_skip_test(pytest.skip.Exception)
+    plugin_base.set_fixture_functions(PytestFixtureFunctions)
 
 
 def pytest_sessionstart(session):
@@ -132,6 +136,7 @@ def pytest_collection_modifyitems(session, config, items):
     rebuilt_items = collections.defaultdict(
         lambda: collections.defaultdict(list)
     )
+
     items[:] = [
         item
         for item in items
@@ -173,21 +178,63 @@ def pytest_collection_modifyitems(session, config, items):
 
 
 def pytest_pycollect_makeitem(collector, name, obj):
-    if inspect.isclass(obj) and plugin_base.want_class(obj):
-        return pytest.Class(name, parent=collector)
+
+    if inspect.isclass(obj) and plugin_base.want_class(name, obj):
+        return [
+            pytest.Class(parametrize_cls.__name__, parent=collector)
+            for parametrize_cls in _parametrize_cls(collector.module, obj)
+        ]
     elif (
         inspect.isfunction(obj)
         and isinstance(collector, pytest.Instance)
         and plugin_base.want_method(collector.cls, obj)
     ):
-        return pytest.Function(name, parent=collector)
+        # None means, fall back to default logic, which includes
+        # method-level parametrize
+        return None
     else:
+        # empty list means skip this item
         return []
 
 
 _current_class = None
 
 
+def _parametrize_cls(module, cls):
+    """implement a class-based version of pytest parametrize."""
+
+    if "_sa_parametrize" not in cls.__dict__:
+        return [cls]
+
+    _sa_parametrize = cls._sa_parametrize
+    classes = []
+    for full_param_set in itertools.product(
+        *[params for argname, params in _sa_parametrize]
+    ):
+        cls_variables = {}
+
+        for argname, param in zip(
+            [_sa_param[0] for _sa_param in _sa_parametrize], full_param_set
+        ):
+            if not argname:
+                raise TypeError("need argnames for class-based combinations")
+            argname_split = re.split(r",\s*", argname)
+            for arg, val in zip(argname_split, param.values):
+                cls_variables[arg] = val
+        parametrized_name = "_".join(
+            # token is a string, but in py2k py.test is giving us a unicode,
+            # so call str() on it.
+            str(re.sub(r"\W", "", token))
+            for param in full_param_set
+            for token in param.id.split("-")
+        )
+        name = "%s_%s" % (cls.__name__, parametrized_name)
+        newcls = type.__new__(type, name, (cls,), cls_variables)
+        setattr(module, name, newcls)
+        classes.append(newcls)
+    return classes
+
+
 def pytest_runtest_setup(item):
     # here we seem to get called only based on what we collected
     # in pytest_collection_modifyitems.   So to do class-based stuff
@@ -239,3 +286,99 @@ def class_setup(item):
 
 def class_teardown(item):
     plugin_base.stop_test_class(item.cls)
+
+
+def getargspec(fn):
+    if sys.version_info.major == 3:
+        return inspect.getfullargspec(fn)
+    else:
+        return inspect.getargspec(fn)
+
+
+class PytestFixtureFunctions(plugin_base.FixtureFunctions):
+    def skip_test_exception(self, *arg, **kw):
+        return pytest.skip.Exception(*arg, **kw)
+
+    _combination_id_fns = {
+        "i": lambda obj: obj,
+        "r": repr,
+        "s": str,
+        "n": operator.attrgetter("__name__"),
+    }
+
+    def combinations(self, *arg_sets, **kw):
+        """facade for pytest.mark.paramtrize.
+
+        Automatically derives argument names from the callable which in our
+        case is always a method on a class with positional arguments.
+
+        ids for parameter sets are derived using an optional template.
+
+        """
+
+        if sys.version_info.major == 3:
+            if len(arg_sets) == 1 and hasattr(arg_sets[0], "__next__"):
+                arg_sets = list(arg_sets[0])
+        else:
+            if len(arg_sets) == 1 and hasattr(arg_sets[0], "next"):
+                arg_sets = list(arg_sets[0])
+
+        argnames = kw.pop("argnames", None)
+
+        id_ = kw.pop("id_", None)
+
+        if id_:
+            _combination_id_fns = self._combination_id_fns
+
+            # because itemgetter is not consistent for one argument vs.
+            # multiple, make it multiple in all cases and use a slice
+            # to omit the first argument
+            _arg_getter = operator.itemgetter(
+                0,
+                *[
+                    idx
+                    for idx, char in enumerate(id_)
+                    if char in ("n", "r", "s", "a")
+                ]
+            )
+            fns = [
+                (operator.itemgetter(idx), _combination_id_fns[char])
+                for idx, char in enumerate(id_)
+                if char in _combination_id_fns
+            ]
+            arg_sets = [
+                pytest.param(
+                    *_arg_getter(arg)[1:],
+                    id="-".join(
+                        comb_fn(getter(arg)) for getter, comb_fn in fns
+                    )
+                )
+                for arg in arg_sets
+            ]
+        else:
+            # ensure using pytest.param so that even a 1-arg paramset
+            # still needs to be a tuple.  otherwise paramtrize tries to
+            # interpret a single arg differently than tuple arg
+            arg_sets = [pytest.param(*arg) for arg in arg_sets]
+
+        def decorate(fn):
+            if inspect.isclass(fn):
+                if "_sa_parametrize" not in fn.__dict__:
+                    fn._sa_parametrize = []
+                fn._sa_parametrize.append((argnames, arg_sets))
+                return fn
+            else:
+                if argnames is None:
+                    _argnames = getargspec(fn).args[1:]
+                else:
+                    _argnames = argnames
+                return pytest.mark.parametrize(_argnames, arg_sets)(fn)
+
+        return decorate
+
+    def param_ident(self, *parameters):
+        ident = parameters[0]
+        return pytest.param(*parameters[1:], id=ident)
+
+    def fixture(self, fn):
+        return pytest.fixture(fn)