diff hgdemandimport/__init__.py @ 37843:670eb4fa1b86

demandimport: make module ignores a set (API)

The list of modules to ignore is used for membership testing. Yet
it is defined as a list.

Sets are more efficient for membership testing. So this commit converts
the module list to a set.

Since we took an API hit, I renamed the variable to further clarify
the change.

This appears to reduce the CPU time for running 300 invocations of
`hg log -r. -T '{rev}'` on my i7-6700K:

before: 18.64s
after:  18.44s

Differential Revision: https://phab.mercurial-scm.org/D3440

--- a/hgdemandimport/__init__.py	Thu Apr 19 20:33:43 2018 +0900
+++ b/hgdemandimport/__init__.py	Sat May 05 18:41:51 2018 -0700
@@ -21,8 +21,9 @@
 else:
     from . import demandimportpy2 as demandimport
 
-# Extensions can add to this list if necessary.
-ignore = [
+# Full module names which can't be lazy imported.
+# Extensions can add to this set.
+IGNORES = {
     '__future__',
     '_hashlib',
     # ImportError during pkg_resources/__init__.py:fixup_namespace_package
@@ -55,17 +56,15 @@
     '__builtin__',
     'builtins',
     'urwid.command_map', # for pudb
-    ]
+}
 
 _pypy = '__pypy__' in sys.builtin_module_names
 
 if _pypy:
-    ignore.extend([
-        # _ctypes.pointer is shadowed by "from ... import pointer" (PyPy 5)
-        '_ctypes.pointer',
-    ])
+    # _ctypes.pointer is shadowed by "from ... import pointer" (PyPy 5)
+    IGNORES.add('_ctypes.pointer')
 
-demandimport.init(ignore)
+demandimport.init(IGNORES)
 
 # Re-export.
 isenabled = demandimport.isenabled