Merge branch 'master' into housekeeping/98-remove-shim

Author: jaraco

.gitlab-ci.yml

@@ -13,18 +13,18 @@ qa:
 
 tests:
   script:
-    - tox -e py27,py34,py35,py36,py37,py38
+    - tox -e py27,py35,py36,py37,py38
 
 coverage:
   script:
-    - tox -e py27-cov,py34-cov,py35-cov,py36-cov,py37-cov,py38-cov
+    - tox -e py27-cov,py35-cov,py36-cov,py37-cov,py38-cov
   artifacts:
     paths:
       - coverage.xml
 
 diffcov:
   script:
-    - tox -e py27-diffcov,py34-diffcov,py35-diffcov,py36-diffcov,py37-diffcov,py38-diffcov
+    - tox -e py27-diffcov,py35-diffcov,py36-diffcov,py37-diffcov,py38-diffcov
 
 docs:
   script:

importlib_metadata/_compat.py

@@ -51,11 +51,35 @@ class MetaPathFinder(object):
 
 
 def install(cls):
-    """Class decorator for installation on sys.meta_path."""
+    """
+    Class decorator for installation on sys.meta_path.
+
+    Adds the backport DistributionFinder to sys.meta_path and
+    attempts to disable the finder functionality of the stdlib
+    DistributionFinder.
+    """
     sys.meta_path.append(cls())
+    disable_stdlib_finder()
     return cls
 
 
+def disable_stdlib_finder():
+    """
+    Give the backport primacy for discovering path-based distributions
+    by monkey-patching the stdlib O_O.
+
+    See #91 for more background for rationale on this sketchy
+    behavior.
+    """
+    def matches(finder):
+        return (
+            finder.__module__ == '_frozen_importlib_external'
+            and hasattr(finder, 'find_distributions')
+            )
+    for finder in filter(matches, sys.meta_path):  # pragma: nocover
+        del finder.find_distributions
+
+
 class NullFinder:
     """
     A "Finder" (aka "MetaClassFinder") that never finds any modules,

importlib_metadata/docs/changelog.rst

@@ -7,6 +7,12 @@ v1.0.0
 
 * Removed compatibility shim introduced in 0.23.
 
+* For better compatibility with the stdlib implementation and to
+  avoid the same distributions being discovered by the stdlib and
+  backport implementations, the backport now disables the
+  stdlib DistributionFinder during initialization (import time).
+  Closes #91 and closes #100.
+
 0.23
 ====
 * Added a compatibility shim to prevent failures on beta releases

importlib_metadata/docs/index.rst

@@ -12,8 +12,9 @@ efficient ``pkg_resources`` package.
 
 ``importlib_metadata`` is a backport of Python 3.8's standard library
 `importlib.metadata`_ module for Python 2.7, and 3.4 through 3.7.  Users of
-Python 3.8 and beyond are encouraged to use the standard library module, and
-in fact for these versions, ``importlib_metadata`` just shadows that module.
+Python 3.8 and beyond are encouraged to use the standard library module.
+When imported on Python 3.8 and later, ``importlib_metadata`` replaces the
+DistributionFinder behavior from the stdlib, but leaves the API in tact.
 Developers looking for detailed API descriptions should refer to the Python
 3.8 standard library documentation.
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = {py27,py34,py35,py36,py37,py38}{,-cov,-diffcov},qa,docs
+envlist = {py27,py35,py36,py37,py38}{,-cov,-diffcov},qa,docs
 skip_missing_interpreters = True