Merge ~cjwatson/lazr.delegates:no-py2 into lazr.delegates:main

[Colin Watson]

Drop Python 2 support

[Jürgen Gmach (jugmac00)]

LGTM with two minor nitpicks

review: Approve

[Jürgen Gmach (jugmac00)]

Looks good! Thank you for the update.

review: Approve

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 8691251..5d1fb12 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -16,3 +16,8 @@ repos:
     rev: ee781d3ce0ddf835267764f27f4ffdd2dd21fa27
     hooks:
     -   id: woke-from-source
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v2.31.0
+    hooks:
+    -   id: pyupgrade
+        args: [--keep-percent-format, --py3-plus]
diff --git a/NEWS.rst b/NEWS.rst
index af21504..80e1684 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -2,12 +2,12 @@
 NEWS for lazr.delegates
 =======================
 
-2.0.5
+2.1.0
 =====
 - Officially add support for Python 3.6, 3.7, 3.8, 3.9, and 3.10.
-- Drop support for Python 3.2, 3.3, and 3.4.
+- Drop support for Python 2, 3.2, 3.3, and 3.4.
 - Test using ``zope.testrunner`` rather than ``nose``.
-- Combine coverage for Python 2 and 3.
+- Bring coverage to 100%.
 
 
 2.0.4 (2017-10-20)
diff --git a/setup.py b/setup.py
index abe2368..9474d1d 100755
--- a/setup.py
+++ b/setup.py
@@ -49,8 +49,6 @@ delegating behavior.
         "License :: OSI Approved :: GNU Library or Lesser General Public License (LGPL)",
         "Operating System :: OS Independent",
         'Programming Language :: Python',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
@@ -59,7 +57,8 @@ delegating behavior.
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         ],
-        extras_require={
-            "docs": ["Sphinx"],
-        },
+    extras_require={
+        "docs": ["Sphinx"],
+    },
+    python_requires=">=3.5",
     )
diff --git a/src/lazr/delegates/__init__.py b/src/lazr/delegates/__init__.py
index b0b15de..eb56e29 100644
--- a/src/lazr/delegates/__init__.py
+++ b/src/lazr/delegates/__init__.py
@@ -17,6 +17,7 @@
 """Decorator helpers that simplify class composition."""
 
 __all__ = [
+    'Passthrough',
     'delegate_to',
     ]
 
@@ -24,14 +25,7 @@ __all__ = [
 from lazr.delegates._version import __version__
 __version__
 
-from lazr.delegates._passthrough import Passthrough
-
-# The class decorator syntax is different in Python 2 vs. Python 3.
-import sys
-if sys.version_info[0] == 2:
-    from lazr.delegates._python2 import delegate_to
-    # The legacy API is only compatible with Python 2.
-    from lazr.delegates._delegates import delegates
-    __all__.append('delegates')
-else:
-    from lazr.delegates._python3 import delegate_to
+from lazr.delegates._delegates import (
+    Passthrough,
+    delegate_to,
+    )
diff --git a/src/lazr/delegates/_delegates.py b/src/lazr/delegates/_delegates.py
index ae09920..eb7c1b3 100644
--- a/src/lazr/delegates/_delegates.py
+++ b/src/lazr/delegates/_delegates.py
@@ -1,4 +1,4 @@
-# Copyright 2008-2015 Canonical Ltd.  All rights reserved.
+# Copyright 2008-2022 Canonical Ltd.  All rights reserved.
 #
 # This file is part of lazr.delegates.
 #
@@ -16,34 +16,22 @@
 
 """Decorator helpers that simplify class composition."""
 
-from __future__ import absolute_import, print_function, unicode_literals
-
-
-__metaclass__ = type
 __all__ = [
-    'delegates',
+    'Passthrough',
+    'delegate_to',
     ]
 
-
-import sys
-from types import ClassType
-
-from zope.interface.advice import addClassAdvisor
 from zope.interface import classImplements
-from zope.interface.interfaces import IInterface
 
-from lazr.delegates._passthrough import Passthrough
 
-
-def delegates(interface_spec, context='context'):
+def delegate_to(*interfaces, context='context'):
     """Make an adapter into a decorator.
 
     Use like:
 
+        @implementer(IRosettaProject)
+        @delegate_to(IProject)
         class RosettaProject:
-            implements(IRosettaProject)
-            delegates(IProject)
-
             def __init__(self, context):
                 self.context = context
 
@@ -53,10 +41,9 @@ def delegates(interface_spec, context='context'):
     If you want to use a different name than "context" then you can explicitly
     say so:
 
+        @implementer(IRosettaProject)
+        @delegate_to(IProject, context='project')
         class RosettaProject:
-            implements(IRosettaProject)
-            delegates(IProject, context='project')
-
             def __init__(self, project):
                 self.project = project
 
@@ -67,45 +54,51 @@ def delegates(interface_spec, context='context'):
 
     The minimal decorator looks like this:
 
+    @delegate_to(IProject)
     class RosettaProject:
-        delegates(IProject)
-
         def __init__(self, context):
             self.context = context
-
     """
-    # pylint: disable-msg=W0212
-    frame = sys._getframe(1)
-    locals = frame.f_locals
-
-    # Try to make sure we were called from a class def
-    if (locals is frame.f_globals) or ('__module__' not in locals):
-        raise TypeError(
-            "delegates() can be used only from a class definition.")
-
-    locals['__delegates_advice_data__'] = interface_spec, context
-    addClassAdvisor(_delegates_advice, depth=2)
-
-
-def _delegates_advice(cls):
-    """Add a Passthrough class for each missing interface attribute.
-
-    This function connects the decorator class to the delegate class.
-    Only new-style classes are supported.
+    if len(interfaces) == 0:
+        raise TypeError('At least one interface is required')
+    def _decorator(cls):
+        missing = object()
+        for interface in interfaces:
+            classImplements(cls, interface)
+            for name in interface:
+                if getattr(cls, name, missing) is missing:
+                    setattr(cls, name, Passthrough(name, context))
+        return cls
+    return _decorator
+
+
+class Passthrough:
+    """Call the delegated class for the decorator class.
+
+    If the ``adaptation`` argument is not None, it should be a callable. It
+    will be called with the context, and should return an object that will
+    have the delegated attribute. The ``adaptation`` argument is expected to
+    be used with an interface, to adapt the context.
     """
-    interface_spec, contextvar = cls.__dict__['__delegates_advice_data__']
-    del cls.__delegates_advice_data__
-    if isinstance(cls, ClassType):
-        raise TypeError(
-            'Cannot use delegates() on a classic class: %s.' % cls)
-    if IInterface.providedBy(interface_spec):
-        interfaces = [interface_spec]
-    else:
-        interfaces = interface_spec
-    not_found = object()
-    for interface in interfaces:
-        classImplements(cls, interface)
-        for name in interface:
-            if getattr(cls, name, not_found) is not_found:
-                setattr(cls, name, Passthrough(name, contextvar))
-    return cls
+    def __init__(self, name, contextvar, adaptation=None):
+        self.name = name
+        self.contextvar = contextvar
+        self.adaptation = adaptation
+
+    def __get__(self, inst, cls=None):
+        if inst is None:
+            return self
+        else:
+            context = getattr(inst, self.contextvar)
+            if self.adaptation is not None:
+                context = self.adaptation(context)
+            return getattr(context, self.name)
+
+    def __set__(self, inst, value):
+        context = getattr(inst, self.contextvar)
+        if self.adaptation is not None:
+            context = self.adaptation(context)
+        setattr(context, self.name, value)
+
+    def __delete__(self, inst):
+        raise NotImplementedError
diff --git a/src/lazr/delegates/_passthrough.py b/src/lazr/delegates/_passthrough.py
 deleted file mode 100644
index 144f689..0000000
--- a/src/lazr/delegates/_passthrough.py
+++ /dev/null
@@ -1,55 +0,0 @@
-# Copyright 2008-2015 Canonical Ltd.  All rights reserved.
-#
-# This file is part of lazr.delegates.
-#
-# lazr.delegates is free software: you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation, version 3 of the License.
-#
-# lazr.delegates is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
-# License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with lazr.delegates.  If not, see <http://www.gnu.org/licenses/>.
-
-from __future__ import absolute_import, print_function, unicode_literals
-
-
-__metaclass__ = type
-__all__ = [
-    'Passthrough',
-    ]
-
-
-class Passthrough:
-    """Call the delegated class for the decorator class.
-
-    If the ``adaptation`` argument is not None, it should be a callable. It
-    will be called with the context, and should return an object that will
-    have the delegated attribute. The ``adaptation`` argument is expected to
-    be used with an interface, to adapt the context.
-    """
-    def __init__(self, name, contextvar, adaptation=None):
-        self.name = name
-        self.contextvar = contextvar
-        self.adaptation = adaptation
-
-    def __get__(self, inst, cls=None):
-        if inst is None:
-            return self
-        else:
-            context = getattr(inst, self.contextvar)
-            if self.adaptation is not None:
-                context = self.adaptation(context)
-            return getattr(context, self.name)
-
-    def __set__(self, inst, value):
-        context = getattr(inst, self.contextvar)
-        if self.adaptation is not None:
-            context = self.adaptation(context)
-        setattr(context, self.name, value)
-
-    def __delete__(self, inst):
-        raise NotImplementedError
diff --git a/src/lazr/delegates/_python2.py b/src/lazr/delegates/_python2.py
 deleted file mode 100644
index 2ce472a..0000000
--- a/src/lazr/delegates/_python2.py
+++ /dev/null
@@ -1,38 +0,0 @@
-# Copyright 2014-2015 Canonical Ltd.  All rights reserved.
-#
-# This file is part of lazr.delegates.
-#
-# lazr.delegates is free software: you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation, version 3 of the License.
-#
-# lazr.delegates is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
-# License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with lazr.delegates.  If not, see <http://www.gnu.org/licenses/>.
-
-"""Class decorator definition for Python 2."""
-
-from zope.interface import classImplements
-
-from lazr.delegates._passthrough import Passthrough
-
-
-def delegate_to(*interfaces, **kws):
-    context = kws.pop('context', 'context')
-    if len(kws) > 0:
-        raise TypeError('Too many arguments')
-    if len(interfaces) == 0:
-        raise TypeError('At least one interface is required')
-    def _decorator(cls):
-        missing = object()
-        for interface in interfaces:
-            classImplements(cls, interface)
-            for name in interface:
-                if getattr(cls, name, missing) is missing:
-                    setattr(cls, name, Passthrough(name, context))
-        return cls
-    return _decorator
diff --git a/src/lazr/delegates/_python3.py b/src/lazr/delegates/_python3.py
 deleted file mode 100644
index f9430f5..0000000
--- a/src/lazr/delegates/_python3.py
+++ /dev/null
@@ -1,38 +0,0 @@
-# Copyright 2014-2015 Canonical Ltd.  All rights reserved.
-#
-# This file is part of lazr.delegates.
-#
-# lazr.delegates is free software: you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation, version 3 of the License.
-#
-# lazr.delegates is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
-# License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with lazr.delegates.  If not, see <http://www.gnu.org/licenses/>.
-
-"""Class decorator definition for Python 3.
-
-This syntax is not legal in Python 2.
-"""
-
-from zope.interface import classImplements
-
-from lazr.delegates._passthrough import Passthrough
-
-
-def delegate_to(*interfaces, context='context'):
-    if len(interfaces) == 0:
-        raise TypeError('At least one interface is required')
-    def _decorator(cls):
-        missing = object()
-        for interface in interfaces:
-            classImplements(cls, interface)
-            for name in interface:
-                if getattr(cls, name, missing) is missing:
-                    setattr(cls, name, Passthrough(name, context))
-        return cls
-    return _decorator
diff --git a/src/lazr/delegates/docs/conf.py b/src/lazr/delegates/docs/conf.py
index fed69d1..adc0c50 100644
--- a/src/lazr/delegates/docs/conf.py
+++ b/src/lazr/delegates/docs/conf.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-#
 # lazr.delegates documentation build configuration file, created by
 # sphinx-quickstart on Mon Jan  7 10:37:37 2013.
 #
diff --git a/src/lazr/delegates/tests/test_api.py b/src/lazr/delegates/tests/test_api.py
index 5ecea47..4f6f200 100644
--- a/src/lazr/delegates/tests/test_api.py
+++ b/src/lazr/delegates/tests/test_api.py
@@ -25,11 +25,4 @@ class TestAPI(unittest.TestCase):
     """Test various corner cases in the API."""
 
     def test_no_interfaces(self):
-        try:
-            @delegate_to()
-            class SomeClass(object):
-                pass
-        except TypeError:
-            pass
-        else:
-            self.fail('TypeError expected')
+        self.assertRaises(TypeError, delegate_to)
diff --git a/src/lazr/delegates/tests/test_docs.py b/src/lazr/delegates/tests/test_docs.py
index 7ca6971..9e19ce4 100644
--- a/src/lazr/delegates/tests/test_docs.py
+++ b/src/lazr/delegates/tests/test_docs.py
@@ -16,9 +16,6 @@
 
 """Test harness for doctests."""
 
-from __future__ import absolute_import, print_function, unicode_literals
-
-__metaclass__ = type
 __all__ = []
 
 import atexit
@@ -50,17 +47,11 @@ def load_tests(loader, tests, pattern):
                     )
                 )
     atexit.register(cleanup_resources)
-    globs = {
-        "absolute_import": absolute_import,
-        "print_function": print_function,
-        "unicode_literals": unicode_literals,
-    }
     tests.addTest(
         doctest.DocFileSuite(
             *doctest_files,
             module_relative=False,
             optionflags=DOCTEST_FLAGS,
-            globs=globs,
             encoding="UTF-8"
         )
     )
diff --git a/src/lazr/delegates/tests/test_passthrough.py b/src/lazr/delegates/tests/test_passthrough.py
index 009ed73..0905e3b 100644
--- a/src/lazr/delegates/tests/test_passthrough.py
+++ b/src/lazr/delegates/tests/test_passthrough.py
@@ -58,13 +58,13 @@ class TestPassthrough(unittest.TestCase):
         # provided, should be a zope.interface.Interface subclass (although in
         # practice any callable will do) to which the instance is adapted
         # before getting/setting the delegated attribute.
-        class HasNoFoo(object):
+        class HasNoFoo:
             _foo = 1
         no_foo = HasNoFoo()
         # ... but IHasFooAdapter uses HasNoFoo._foo to provide its own .foo,
         # so it works like an adapter for HasNoFoo into some interface that
         # provides a 'foo' attribute.
-        class IHasFooAdapter(object):
+        class IHasFooAdapter:
             def __init__(self, inst):
                 self.inst = inst
             @property
@@ -74,7 +74,7 @@ class TestPassthrough(unittest.TestCase):
             def foo(self, value):
                 self.inst._foo = value
 
-        class Example(object):
+        class Example:
             context = no_foo
 
         p = Passthrough('foo', 'context', adaptation=IHasFooAdapter)
diff --git a/src/lazr/delegates/tests/test_python2.py b/src/lazr/delegates/tests/test_python2.py
 deleted file mode 100644
index ad3de7e..0000000
--- a/src/lazr/delegates/tests/test_python2.py
+++ /dev/null
@@ -1,159 +0,0 @@
-# Copyright 2013-2015 Canonical Ltd.  All rights reserved.
-#
-# This file is part of lazr.delegates.
-#
-# lazr.delegates is free software: you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation, version 3 of the License.
-#
-# lazr.delegates is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
-# License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with lazr.delegates.  If not, see <http://www.gnu.org/licenses/>.
-
-"""Test the legacy API, which only works in Python 2.
-
-All of these tests are copied almost verbatim from the old README.rst.
-"""
-
-
-from __future__ import absolute_import, print_function, unicode_literals
-
-
-# Don't enable the following or we can't test classic class failures.
-#__metaclass__ = type
-__all__ = [
-    'TestLegacyAPI',
-    ]
-
-
-import sys
-import unittest
-
-from zope.interface import Attribute, Interface, implements, providedBy
-
-from lazr.delegates import delegate_to
-if sys.version_info[0] == 2:
-    from lazr.delegates import delegates
-
-
-class IFoo0(Interface):
-    spoo = Attribute('attribute in IFoo0')
-
-class IFoo(IFoo0):
-    def bar():
-        'some method'
-    baz = Attribute('some attribute')
-
-class BaseFoo0:
-    spoo = 'some spoo'
-
-class BaseFoo(BaseFoo0):
-    def bar(self):
-        return 'bar'
-    baz = 'hi baz!'
-
-class IOther(Interface):
-    another = Attribute('another attribute')
-
-class BaseOtherFoo(BaseFoo):
-    another = 'yes, another'
-
-
[e-mail](sys.version_info[0] > 2, "only relevant in Python 2")
-class TestLegacyAPI(unittest.TestCase):
-    def test_basic_usage(self):
-        class SomeClass(object):
-            delegates(IFoo)
-            def __init__(self, context):
-                self.context = context
-
-        f = BaseFoo()
-        s = SomeClass(f)
-        self.assertEqual(s.bar(), 'bar')
-        self.assertEqual(s.baz, 'hi baz!')
-        self.assertEqual(s.spoo, 'some spoo')
-        self.assertTrue(IFoo.providedBy(s))
-
-    def test_keyword_context(self):
-        class SomeOtherClass(object):
-            delegates(IFoo, context='myfoo')
-            def __init__(self, foo):
-                self.myfoo = foo
-            spoo = 'spoo from SomeOtherClass'
-
-        f = BaseFoo()
-        s = SomeOtherClass(f)
-        self.assertEqual(s.bar(), 'bar')
-        self.assertEqual(s.baz, 'hi baz!')
-        self.assertEqual(s.spoo, 'spoo from SomeOtherClass')
-
-        s.baz = 'fish'
-        self.assertEqual(s.baz, 'fish')
-        self.assertEqual(f.baz, 'fish')
-
-    def test_classic_is_error(self):
-        try:
-            class SomeClassicClass:
-                delegates(IFoo)
-        except TypeError:
-            pass
-        else:
-            self.fail('TypeError expected')
-
-    def test_use_outside_class_is_error(self):
-        self.assertRaises(TypeError, delegates, IFoo)
-
-    def test_multiple_interfaces(self):
-        class SomeOtherClass(object):
-            delegates([IFoo, IOther])
-
-        s = SomeOtherClass()
-        s.context = BaseOtherFoo()
-        self.assertEqual(s.another, 'yes, another')
-        self.assertEqual(s.baz, 'hi baz!')
-        self.assertEqual(s.spoo, 'some spoo')
-        self.assertTrue(IFoo.providedBy(s))
-        self.assertTrue(IOther.providedBy(s))
-
-    def test_decorate_existing_object(self):
-        class MoreFoo(BaseFoo, BaseOtherFoo):
-            implements([IFoo, IOther])
-
-        foo = MoreFoo()
-
-        class WithExtraTeapot(object):
-            delegates(providedBy(foo))
-            teapot = 'i am a teapot'
-
-        foo_with_teapot = WithExtraTeapot()
-        foo_with_teapot.context = foo
-
-        self.assertEqual(foo_with_teapot.baz, 'hi baz!')
-        self.assertEqual(foo_with_teapot.another, 'yes, another')
-        self.assertEqual(foo_with_teapot.teapot, 'i am a teapot')
-        self.assertTrue(IFoo.providedBy(foo_with_teapot))
-        self.assertTrue(IOther.providedBy(foo_with_teapot))
-
-
[e-mail](sys.version_info[0] > 2, "only relevant in Python 2")
-class TestNewAPI(unittest.TestCase):
-    """Test corner cases in Python 2.
-
-    Most of the new API is tested in the doctest.  The implementation of the
-    new API is different between Python 2 and Python 3, so test these corner
-    cases.
-    """
-    def test_type_error(self):
-        # Too many arguments to @delegate_to() raises a TypeError.
-        try:
-            @delegate_to(IFoo0, context='myfoo', other='bogus')
-            class SomeClass(object):
-                pass
-        except TypeError:
-            pass
-        else:
-            self.fail('TypeError expected')
diff --git a/tox.ini b/tox.ini
index 7bdfc27..451caed 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,6 @@
 [tox]
 envlist =
     lint
-    py27
     py35
     py36
     py37
@@ -13,11 +12,9 @@ envlist =
 
 [testenv]
 deps =
-    .
     zope.testrunner
-    coverage
 commands =
-    coverage run -m zope.testrunner --test-path src --tests-pattern ^tests {posargs}
+    zope-testrunner --test-path src --tests-pattern ^tests {posargs}
 
 [testenv:lint]
 basepython = python3.8
@@ -36,22 +33,19 @@ deps =
     .[docs]
 
 [testenv:coverage]
-description = Run coverage either via `tox` or `tox -e py27,py38,coverage`
 basepython = python3
-skip_install = true
-depends =
-    py27
-    py38
 deps =
     coverage
+    zope.testrunner
 commands =
-    coverage combine
-    coverage report -m --fail-under=97
+    coverage erase
+    coverage run -m zope.testrunner --test-path src --tests-pattern ^tests {posargs}
+    coverage html
+    coverage report -m --fail-under=100
 
 [coverage:run]
 source = lazr.delegates
 omit = */docs/conf.py
-parallel = true
 
 [coverage:paths]
 source =