Cache supported tags for wheels.

This fixes https://github.com/pypa/setuptools/issues/3804

1 files changed, 11 insertions, 4 deletions

diff --git a/setuptools/wheel.py b/setuptools/wheel.py
index e388083b..aab7ed05 100644
--- a/setuptools/wheel.py
+++ b/setuptools/wheel.py
@@ -27,6 +27,8 @@ WHEEL_NAME = re.compile(
 NAMESPACE_PACKAGE_INIT = \
     "__import__('pkg_resources').declare_namespace(__name__)\n"
 
+_supported_tags = None
+
 
 def unpack(src_dir, dst_dir):
     '''Move everything under `src_dir` to `dst_dir`, and delete the former.'''
@@ -82,10 +84,15 @@ class Wheel:
         )
 
     def is_compatible(self):
-        '''Is the wheel is compatible with the current platform?'''
-        supported_tags = set(
-            (t.interpreter, t.abi, t.platform) for t in sys_tags())
-        return next((True for t in self.tags() if t in supported_tags), False)
+        '''Is the wheel compatible with the current platform?'''
+        global _supported_tags
+        if _supported_tags is None:
+            # We calculate the supported tags only once, otherwise calling
+            # this method on thousands of wheels takes seconds instead of
+            # milliseconds.
+            _supported_tags = set(
+                (t.interpreter, t.abi, t.platform) for t in sys_tags())
+        return next((True for t in self.tags() if t in _supported_tags), False)
 
     def egg_name(self):
         return _egg_basename(