Merge pull request #29567 from Rostepher/cache-utils

[Build System: build-script] Adds a new cache_utils module to build_swift which replaces the existing module from swift_build_support.

Author: Rostepher

utils/build_swift/build_swift/cache_utils.py

@@ -0,0 +1,69 @@
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+# See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+
+"""
+Cache related utitlity functions and decorators.
+"""
+
+
+from __future__ import absolute_import, unicode_literals
+
+import functools
+
+
+__all__ = [
+    'cache',
+    'reify',
+]
+
+
+def cache(func):
+    """Decorator that caches result of a function call.
+
+    NOTE: This decorator does not play nice with methods as the created cache
+    is not instance-local, rather it lives in the decorator.
+    NOTE: When running in Python 3.2 or newer this decorator is replaced with
+    the standard `functools.lru_cache` using a maxsize of None.
+    """
+
+    # Use the standard functools.lru_cache decorator for Python 3.2 and newer.
+    if hasattr(functools, 'lru_cache'):
+        return functools.lru_cache(maxsize=None)(func)
+
+    # Otherwise use a naive caching strategy.
+    _cache = {}
+
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        key = tuple(args) + tuple(kwargs.items())
+
+        if key not in _cache:
+            result = func(*args, **kwargs)
+            _cache[key] = result
+            return result
+
+        return _cache[key]
+    return wrapper
+
+
+def reify(func):
+    """Decorator that replaces the wrapped method with the result after the
+    first call. Used to wrap property-like methods with no arguments.
+    """
+
+    class wrapper(object):
+        def __get__(self, obj, type=None):
+            if obj is None:
+                return self
+
+            result = func(obj)
+            setattr(obj, func.__name__, result)
+            return result
+
+    return functools.update_wrapper(wrapper(), func)

utils/build_swift/tests/build_swift/test_cache_utils.py

@@ -0,0 +1,121 @@
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+# See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+
+from __future__ import absolute_import, unicode_literals
+
+import unittest
+
+from build_swift import cache_utils
+
+from .. import utils
+
+
+try:
+    # Python 3.3
+    from unittest import mock
+except ImportError:
+    mock = None
+
+
+class _CallCounter(object):
+    """Callable helper class used to count and return the number of times an
+    instance has been called.
+    """
+
+    def __init__(self):
+        self._counter = 0
+
+    def __call__(self, *args, **kwargs):
+        count = self._counter
+        self._counter += 1
+        return count
+
+
+class TestCache(unittest.TestCase):
+    """Unit tests for the cache decorator in the cache_utils module.
+    """
+
+    @utils.requires_module('unittest.mock')
+    @utils.requires_python('3.2')  # functools.lru_cache
+    def test_replaced_with_functools_lru_cache_python_3_2(self):
+        with mock.patch('functools.lru_cache') as mock_lru_cache:
+            @cache_utils.cache
+            def func():
+                return None
+
+        mock_lru_cache.assert_called()
+
+    def test_call_with_no_args(self):
+        # Increments the counter once per unique call.
+        counter = _CallCounter()
+
+        @cache_utils.cache
+        def func(*args, **kwargs):
+            return counter(*args, **kwargs)
+
+        self.assertEqual(func(), 0)
+        self.assertEqual(func(), 0)
+
+    def test_call_with_args(self):
+        # Increments the counter once per unique call.
+        counter = _CallCounter()
+
+        @cache_utils.cache
+        def func(*args, **kwargs):
+            return counter(*args, **kwargs)
+
+        self.assertEqual(func(0), 0)
+        self.assertEqual(func(0), 0)
+
+        self.assertEqual(func(1), 1)
+        self.assertEqual(func(1), 1)
+
+        self.assertEqual(func(2), 2)
+        self.assertEqual(func(2), 2)
+
+    def test_call_with_args_and_kwargs(self):
+        # Increments the counter once per unique call.
+        counter = _CallCounter()
+
+        @cache_utils.cache
+        def func(*args, **kwargs):
+            return counter(*args, **kwargs)
+
+        self.assertEqual(func(n=0), 0)
+        self.assertEqual(func(n=0), 0)
+
+        self.assertEqual(func(a=1, b='b'), 1)
+        self.assertEqual(func(a=1, b='b'), 1)
+
+        self.assertEqual(func(0, x=1, y=2.0), 2)
+        self.assertEqual(func(0, x=1, y=2.0), 2)
+
+
+class TestReify(unittest.TestCase):
+    """Unit tests for the reify decorator in the cache_utils module.
+    """
+
+    def test_replaces_attr_after_first_call(self):
+        class Counter(object):
+            def __init__(self):
+                self._counter = 0
+
+            @cache_utils.reify
+            def count(self):
+                count = self._counter
+                self._counter += 1
+                return count
+
+        counter = Counter()
+
+        self.assertEqual(counter.count, 0)
+        self.assertEqual(counter.count, 0)
+
+        # Assert that the count property has been replaced with the constant.
+        self.assertEqual(getattr(counter, 'count'), 0)

utils/build_swift/tests/utils.py

@@ -15,9 +15,11 @@
 import sys
 import unittest
 
-from six import StringIO
+from build_swift import cache_utils
+from build_swift.versions import Version
 
-from swift_build_support.swift_build_support import cache_util
+import six
+from six import StringIO
 
 
 __all__ = [
@@ -27,6 +29,7 @@
     'requires_attr',
     'requires_module',
     'requires_platform',
+    'requires_python',
 
     'BUILD_SCRIPT_IMPL_PATH',
     'BUILD_SWIFT_PATH',
@@ -38,6 +41,8 @@
 # -----------------------------------------------------------------------------
 # Constants
 
+_PYTHON_VERSION = Version(platform.python_version())
+
 TESTS_PATH = os.path.abspath(os.path.dirname(__file__))
 BUILD_SWIFT_PATH = os.path.abspath(os.path.join(TESTS_PATH, os.pardir))
 UTILS_PATH = os.path.abspath(os.path.join(BUILD_SWIFT_PATH, os.pardir))
@@ -124,9 +129,10 @@ def __exit__(self, exc_type, exc_value, traceback):
         sys.stderr = self._old_stdout
 
 
-@cache_util.cached
+@cache_utils.cache
 def requires_attr(obj, attr):
-    """
+    """Decorator used to skip tests if an object does not have the required
+    attribute.
     """
 
     try:
@@ -137,7 +143,7 @@ def requires_attr(obj, attr):
             attr, obj))
 
 
-@cache_util.cached
+@cache_utils.cache
 def requires_module(fullname):
     """Decorator used to skip tests if a module is not imported.
     """
@@ -148,7 +154,7 @@ def requires_module(fullname):
     return unittest.skip('Unable to import "{}"'.format(fullname))
 
 
-@cache_util.cached
+@cache_utils.cache
 def requires_platform(name):
     """Decorator used to skip tests if not running on the given platform.
     """
@@ -157,4 +163,20 @@ def requires_platform(name):
         return lambda func: func
 
     return unittest.skip(
-        'Required platform "{}"" does not match system'.format(name))
+        'Required platform "{}" does not match system'.format(name))
+
+
+@cache_utils.cache
+def requires_python(version):
+    """Decorator used to skip tests if the running Python version is not
+    greater or equal to the required version.
+    """
+
+    if isinstance(version, six.string_types):
+        version = Version(version)
+
+    if _PYTHON_VERSION >= version:
+        return lambda func: func
+
+    return unittest.skip(
+        'Requires Python version {} or greater'.format(version))

utils/swift_build_support/swift_build_support/cache_util.py

@@ -18,10 +18,10 @@
 import platform
 import sys
 
+from build_swift.build_swift import cache_utils
 from build_swift.build_swift.wrappers import xcrun
 
 from . import product
-from .. import cache_util
 from .. import shell
 
 
@@ -44,7 +44,7 @@ def __init__(self, product_class, args, toolchain, workspace):
         self.args = args
         self.toolchain = toolchain
 
-    @cache_util.reify
+    @cache_utils.reify
     def ninja_bin_path(self):
         return os.path.join(self.build_dir, 'ninja')
 

utils/swift_build_support/swift_build_support/products/ninja.py

@@ -18,10 +18,10 @@
 
 import platform
 
+from build_swift.build_swift import cache_utils
 from build_swift.build_swift.shell import which
 from build_swift.build_swift.wrappers import xcrun
 
-from . import cache_util
 from . import shell
 
 
@@ -44,7 +44,7 @@ def _register(name, *tool):
     def _getter(self):
         return self.find_tool(*tool)
     _getter.__name__ = name
-    setattr(Toolchain, name, cache_util.reify(_getter))
+    setattr(Toolchain, name, cache_utils.reify(_getter))
 
 
 if platform.system() == 'Windows':
@@ -162,7 +162,7 @@ def __init__(self):
             suffixes = ['38', '37', '36', '35']
         super(FreeBSD, self).__init__(suffixes)
 
-    @cache_util.reify
+    @cache_utils.reify
     def _release_date(self):
         """Return the release date for FreeBSD operating system on this host.
         If the release date cannot be ascertained, return None.