Opt: Patch pkg_resources for faster startup

module/device/device.py

@@ -1,6 +1,12 @@
 import collections
 import itertools
 
+# Patch pkg_resources before importing adbutils and uiautomator2
+from module.device.pkg_resources import get_distribution
+
+# Just avoid being removed by import optimization
+_ = get_distribution
+
 from module.base.timer import Timer
 from module.device.app_control import AppControl
 from module.device.control import Control

module/device/pkg_resources/__init__.py

@@ -0,0 +1,82 @@
+import os
+import re
+import sys
+
+from module.base.decorator import cached_property
+
+"""
+Importing pkg_resources is so slow, like 0.4 ~ 1.0s, just google it you will find it indeed really slow.
+Since it was some kind of standard library there is no way to modify it or speed it up.
+So here's a poor but fast implementation of pkg_resources returning the things in need.
+
+To patch:
+```
+# Patch pkg_resources before importing adbutils and uiautomator2
+from module.device.pkg_resources import get_distribution
+# Just avoid being removed by import optimization
+_ = get_distribution
+```
+"""
+# Inject sys.modules, pretend we have pkg_resources imported
+sys.modules['pkg_resources'] = sys.modules['module.device.pkg_resources']
+
+
+class FakeDistributionObject:
+    def __init__(self, dist, version):
+        self.dist = dist
+        self.version = version
+
+    def __str__(self):
+        return f'{self.__class__.__name__}({self.dist}={self.version})'
+
+    __repr__ = __str__
+
+
+class PackageCache:
+    @cached_property
+    def site_packages(self):
+        # Just whatever library to locate the `site-packages` directory
+        import requests
+        path = os.path.abspath(os.path.join(requests.__file__, '../../'))
+        return path
+
+    @cached_property
+    def dict_installed_packages(self):
+        """
+        Returns:
+            dict: Key: str, package name
+                Value: FakeDistributionObject
+        """
+        dic = {}
+        for file in os.listdir(self.site_packages):
+            # mxnet_cu101-1.6.0.dist-info
+            res = re.match(r'^(.+)-(.+)\.dist-info$', file)
+            if res:
+                obj = FakeDistributionObject(
+                    dist=res.group(1),
+                    version=res.group(2),
+                )
+                dic[obj.dist] = obj
+
+        return dic
+
+
+PACKAGE_CACHE = PackageCache()
+
+
+def resource_filename(*args):
+    if args == ("adbutils", "binaries"):
+        path = os.path.abspath(os.path.join(PACKAGE_CACHE.site_packages, *args))
+        return path
+
+
+def get_distribution(dist):
+    """Return a current distribution object for a Requirement or string"""
+    if dist == 'adbutils':
+        return PACKAGE_CACHE.dict_installed_packages.get('adbutils', '0.11.0')
+    if dist == 'uiautomator2':
+        return PACKAGE_CACHE.dict_installed_packages.get('uiautomator2', '2.16.17')
+
+
+class DistributionNotFound(Exception):
+    pass