Implement persistent caching for simplify_condition

Store the results of simplify_condition in a json cache file,
next to the pro2cmake.py script.
Dramatically speeds up re-conversion of projects.

The cache is cleared whenever the content of the
condition_simplifier.py file changes, effectively presuming that the
condition computing code has changed.

Sample times.
Initial corelib.pro conversion - 142.13 seconds.
Next re-conversion with hot cache - 1.17 seconds.

Change-Id: I8790b2736358236e4b23bcb5f10f45a36fdfa426
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Qt CMake Build Bot

2 files changed, 115 insertions, 1 deletions

diff --git a/util/cmake/condition_simplifier.py b/util/cmake/condition_simplifier.py
index c67b78ffad..de329be1d4 100644
--- a/util/cmake/condition_simplifier.py
+++ b/util/cmake/condition_simplifier.py
@@ -29,8 +29,8 @@
 
 
 import re
-
 from sympy import simplify_logic, And, Or, Not, SympifyError
+from condition_simplifier_cache import simplify_condition_memoize
 
 
 def _iterate_expr_tree(expr, op, matches):
@@ -160,6 +160,7 @@ def _recursive_simplify(expr):
     return expr
 
 
+@simplify_condition_memoize
 def simplify_condition(condition: str) -> str:
     input_condition = condition.strip()
 
diff --git a/util/cmake/condition_simplifier_cache.py b/util/cmake/condition_simplifier_cache.py
new file mode 100644
index 0000000000..b405ef23f8
--- /dev/null
+++ b/util/cmake/condition_simplifier_cache.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+#############################################################################
+##
+## Copyright (C) 2018 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the plugins of the Qt Toolkit.
+##
+## $QT_BEGIN_LICENSE:GPL-EXCEPT$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 3 as published by the Free Software
+## Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+
+import atexit
+import hashlib
+import json
+import os
+import sys
+import time
+
+from typing import Callable
+
+
+def get_current_file_path() -> str:
+    try:
+        this_file = __file__
+    except NameError:
+        this_file = sys.argv[0]
+    this_file = os.path.abspath(this_file)
+    return this_file
+
+
+def get_cache_location() -> str:
+    this_file = get_current_file_path()
+    dir_path = os.path.dirname(this_file)
+    cache_path = os.path.join(dir_path, ".pro2cmake_cache", "cache.json")
+    return cache_path
+
+
+def get_file_checksum(file_path: str) -> str:
+    try:
+        with open(file_path, "r") as content_file:
+            content = content_file.read()
+    except IOError:
+        content = time.time()
+    checksum = hashlib.md5(content.encode("utf-8")).hexdigest()
+    return checksum
+
+
+def get_condition_simplifier_checksum() -> str:
+    current_file_path = get_current_file_path()
+    dir_name = os.path.dirname(current_file_path)
+    condition_simplifier_path = os.path.join(dir_name, "condition_simplifier.py")
+    return get_file_checksum(condition_simplifier_path)
+
+
+def init_cache_dict():
+    return {
+        "checksum": get_condition_simplifier_checksum(),
+        "schema_version": "1",
+        "cache": {"conditions": {}},
+    }
+
+
+def simplify_condition_memoize(f: Callable[[str], str]):
+    cache_path = get_cache_location()
+    cache_file_content = None
+
+    if os.path.exists(cache_path):
+        try:
+            with open(cache_path, "r") as cache_file:
+                cache_file_content = json.load(cache_file)
+        except (IOError, ValueError):
+            pass
+
+    if not cache_file_content:
+        cache_file_content = init_cache_dict()
+
+    current_checksum = get_condition_simplifier_checksum()
+    if cache_file_content["checksum"] != current_checksum:
+        cache_file_content = init_cache_dict()
+
+    def update_cache_file():
+        if not os.path.exists(cache_path):
+            os.makedirs(os.path.dirname(cache_path), exist_ok=True)
+        with open(cache_path, "w") as cache_file_write_handle:
+            json.dump(cache_file_content, cache_file_write_handle, indent=4)
+
+    atexit.register(update_cache_file)
+
+    def helper(condition: str) -> str:
+        if condition not in cache_file_content["cache"]["conditions"]:
+            cache_file_content["cache"]["conditions"][condition] = f(condition)
+        return cache_file_content["cache"]["conditions"][condition]
+
+    return helper