[RFC] Introduce attrs

_pytest/fixtures.py

@@ -7,6 +7,7 @@
 import py
 from py._code.code import FormattedExcinfo
 
+import attr
 import _pytest
 from _pytest import nodes
 from _pytest._code.code import TerminalRepr
@@ -822,13 +823,21 @@ def pytest_fixture_setup(fixturedef, request):
     return result
 
 
-class FixtureFunctionMarker:
-    def __init__(self, scope, params, autouse=False, ids=None, name=None):
-        self.scope = scope
-        self.params = params
-        self.autouse = autouse
-        self.ids = ids
-        self.name = name
+def _ensure_immutable_ids(ids):
+    if ids is None:
+        return
+    if callable(ids):
+        return ids
+    return tuple(ids)
+
+
+@attr.s(frozen=True)
+class FixtureFunctionMarker(object):
+    scope = attr.ib()
+    params = attr.ib(convert=attr.converters.optional(tuple))
+    autouse = attr.ib(default=False)
+    ids = attr.ib(default=None, convert=_ensure_immutable_ids)
+    name = attr.ib(default=None)
 
     def __call__(self, function):
         if isclass(function):

_pytest/mark.py

@@ -3,6 +3,7 @@
 
 import inspect
 import warnings
+import attr
 from collections import namedtuple
 from operator import attrgetter
 from six.moves import map
@@ -185,22 +186,26 @@ def pytest_collection_modifyitems(items, config):
         items[:] = remaining
 
 
-class MarkMapping:
+@attr.s
+class MarkMapping(object):
     """Provides a local mapping for markers where item access
     resolves to True if the marker is present. """
 
-    def __init__(self, keywords):
-        mymarks = set()
+    own_mark_names = attr.ib()
+
+    @classmethod
+    def from_keywords(cls, keywords):
+        mark_names = set()
         for key, value in keywords.items():
             if isinstance(value, MarkInfo) or isinstance(value, MarkDecorator):
-                mymarks.add(key)
-        self._mymarks = mymarks
+                mark_names.add(key)
+        return cls(mark_names)
 
     def __getitem__(self, name):
-        return name in self._mymarks
+        return name in self.own_mark_names
 
 
-class KeywordMapping:
+class KeywordMapping(object):
     """Provides a local mapping for keywords.
     Given a list of names, map any substring of one of these names to True.
     """
@@ -217,7 +222,7 @@ def __getitem__(self, subname):
 
 def matchmark(colitem, markexpr):
     """Tries to match on any marker names, attached to the given colitem."""
-    return eval(markexpr, {}, MarkMapping(colitem.keywords))
+    return eval(markexpr, {}, MarkMapping.from_keywords(colitem.keywords))
 
 
 def matchkeyword(colitem, keywordexpr):
@@ -306,7 +311,21 @@ def istestfunc(func):
         getattr(func, "__name__", "<lambda>") != "<lambda>"
 
 
-class MarkDecorator:
+@attr.s(frozen=True)
+class Mark(object):
+    name = attr.ib()
+    args = attr.ib()
+    kwargs = attr.ib()
+
+    def combined_with(self, other):
+        assert self.name == other.name
+        return Mark(
+            self.name, self.args + other.args,
+            dict(self.kwargs, **other.kwargs))
+
+
+@attr.s
+class MarkDecorator(object):
     """ A decorator for test functions and test classes.  When applied
     it will create :class:`MarkInfo` objects which may be
     :ref:`retrieved by hooks as item keywords <excontrolskip>`.
@@ -340,9 +359,7 @@ def test_function():
 
     """
 
-    def __init__(self, mark):
-        assert isinstance(mark, Mark), repr(mark)
-        self.mark = mark
+    mark = attr.ib(validator=attr.validators.instance_of(Mark))
 
     name = alias('mark.name')
     args = alias('mark.args')
@@ -422,15 +439,6 @@ def store_legacy_markinfo(func, mark):
         holder.add_mark(mark)
 
 
-class Mark(namedtuple('Mark', 'name, args, kwargs')):
-
-    def combined_with(self, other):
-        assert self.name == other.name
-        return Mark(
-            self.name, self.args + other.args,
-            dict(self.kwargs, **other.kwargs))
-
-
 class MarkInfo(object):
     """ Marking object created by :class:`MarkDecorator` instances. """
 

changelog/2641.trivial

@@ -0,0 +1 @@
+pytest now depends on `attrs <https://pypi.org/project/attrs/>`_ for internal structures to ease code maintainability.

setup.py

@@ -43,8 +43,13 @@ def has_environment_marker_support():
 
 
 def main():
-    install_requires = ['py>=1.4.34', 'six>=1.10.0', 'setuptools']
     extras_require = {}
+    install_requires = [
+        'py>=1.4.33',
+        'six>=1.10.0',
+        'setuptools',
+        'attrs>=17.2.0',
+    ]
     # if _PYTEST_SETUP_SKIP_PLUGGY_DEP is set, skip installing pluggy;
     # used by tox.ini to test with pluggy master
     if '_PYTEST_SETUP_SKIP_PLUGGY_DEP' not in os.environ: