[build-script] Introduced cached method/function decorator

cache_util.cached: cached function/method result associated with arguments.
cache_util.reifry: replace attribute with the result of the method.

Author: rintaro

utils/swift_build_support/swift_build_support/cache_util.py

@@ -0,0 +1,58 @@
+# swift_build_support/cache_util.py -----------------------------*- python -*-
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+#
+# ----------------------------------------------------------------------------
+"""
+Cache related utilities
+"""
+# ----------------------------------------------------------------------------
+
+from functools import update_wrapper
+
+__all__ = [
+    'cached',
+    'reify'
+]
+
+
+def cached(func):
+    """Decorator that caches result of method or function.
+
+    Note: Support method or function.
+    """
+    cache = {}
+
+    def wrapper(*args, **kwargs):
+        key = tuple(args) + tuple(kwargs.items())
+        if key not in cache:
+            result = func(*args, **kwargs)
+            cache[key] = result
+            return result
+        else:
+            return cache[key]
+
+    return update_wrapper(wrapper, func)
+
+
+def reify(func):
+    """Decorator that replaces the wrapped method with the result after the
+    first call.
+
+    Note: Support method that takes no arguments.
+    """
+    class wrapper(object):
+        def __get__(self, obj, objtype=None):
+            if obj is None:
+                return self
+            result = func(obj)
+            setattr(obj, func.__name__, result)
+            return result
+
+    return update_wrapper(wrapper(), func)

utils/swift_build_support/tests/test_cache_util.py

@@ -0,0 +1,99 @@
+# tests/test_cache_util.py --------------------------------------*- python -*-
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+#
+# ----------------------------------------------------------------------------
+
+import unittest
+
+from swift_build_support import cache_util
+
+
+my_func_called = 0
+my_kfunc_called = 0
+
+
+@cache_util.cached
+def my_func(arg1, arg2):
+    global my_func_called
+    my_func_called += 1
+    return "my_func_result(%s, %s)" % (arg1, arg2)
+
+
+@cache_util.cached
+def my_kfunc(arg1, arg2):
+    global my_kfunc_called
+    my_kfunc_called += 1
+    return "my_kfunc_result(%s, %s)" % (arg1, arg2)
+
+
+class MyClass(object):
+    def __init__(self, prop=None):
+        self.my_method_called = 0
+        self.my_prop_called = 0
+        self.prop_value = prop
+
+    @cache_util.cached
+    def my_method(self, arg1, arg2):
+        self.my_method_called += 1
+        return "my_meth_result(%s, %s)" % (arg1, arg2)
+
+    @cache_util.reify
+    def my_prop(self):
+        self.my_prop_called += 1
+        return "==%s==" % (self.prop_value)
+
+
+class CacheUtilTestCase(unittest.TestCase):
+    def test_cached_func(self):
+        self.assertEqual(my_func("foo", 42), "my_func_result(foo, 42)")
+        self.assertEqual(my_func_called, 1)
+        self.assertEqual(my_func("foo", 42), "my_func_result(foo, 42)")
+        self.assertEqual(my_func_called, 1)
+        self.assertEqual(my_func("bar", 42), "my_func_result(bar, 42)")
+        self.assertEqual(my_func_called, 2)
+        self.assertEqual(my_func("foo", 42), "my_func_result(foo, 42)")
+        self.assertEqual(my_func_called, 2)
+
+    def test_cached_kwfunc(self):
+        self.assertEqual(my_kfunc("foo", arg2=42), "my_kfunc_result(foo, 42)")
+        self.assertEqual(my_kfunc_called, 1)
+        self.assertEqual(my_kfunc("foo", arg2=42), "my_kfunc_result(foo, 42)")
+        self.assertEqual(my_kfunc_called, 1)
+        self.assertEqual(my_kfunc("bar", arg2=42), "my_kfunc_result(bar, 42)")
+        self.assertEqual(my_kfunc_called, 2)
+        self.assertEqual(my_kfunc("foo", arg2=42), "my_kfunc_result(foo, 42)")
+        self.assertEqual(my_kfunc_called, 2)
+
+    def test_cached_method(self):
+        obj1 = MyClass()
+        self.assertEqual(obj1.my_method("foo", 42), "my_meth_result(foo, 42)")
+        self.assertEqual(obj1.my_method_called, 1)
+        self.assertEqual(obj1.my_method("foo", 42), "my_meth_result(foo, 42)")
+        self.assertEqual(obj1.my_method_called, 1)
+        self.assertEqual(obj1.my_method("bar", 12), "my_meth_result(bar, 12)")
+        self.assertEqual(obj1.my_method_called, 2)
+
+        # Test for instance independency.
+        obj2 = MyClass()
+        self.assertEqual(obj2.my_method("foo", 42), "my_meth_result(foo, 42)")
+        self.assertEqual(obj2.my_method_called, 1)
+        self.assertEqual(obj1.my_method_called, 2)
+
+    def test_reify(self):
+        obj1 = MyClass(prop='foo')
+        self.assertEqual(obj1.my_prop, '==foo==')
+        self.assertEqual(obj1.my_prop_called, 1)
+        self.assertEqual(obj1.my_prop, '==foo==')
+        self.assertEqual(obj1.my_prop_called, 1)
+
+        # Test for instance independency.
+        obj2 = MyClass(prop='bar')
+        self.assertEqual(obj2.my_prop, '==bar==')
+        self.assertEqual(obj1.my_prop, '==foo==')