Rewrite selective PIP_IGNORE_REQUIRES_PYTHON to allow test dependencies in metadata to be installed without ignoring REQUIRES_PYTHON

1 files changed, 32 insertions, 7 deletions

diff --git a/tools/tox_pip.py b/tools/tox_pip.py
index 1b7eeda5..6f457bb2 100644
--- a/tools/tox_pip.py
+++ b/tools/tox_pip.py
@@ -38,18 +38,43 @@ def is_install_self(args):
     )
 
 
-def pip(args):
-    # Honor requires-python when installing test suite dependencies
-    if any('-r' in arg for arg in args):
-        os.environ['PIP_IGNORE_REQUIRES_PYTHON'] = '0'
+def pip(*args):
+    cmd = [sys.executable, '-m', 'pip'] + list(args)
+    return subprocess.check_call(cmd)
 
+
+def test_dependencies():
+    from ConfigParser import ConfigParser
+
+    def clean(dep):
+        spec, _, _ = dep.partition('#')
+        return spec.strip()
+
+    parser = ConfigParser()
+    parser.read('setup.cfg')
+    raw = parser.get('options.extras_require', 'tests').split('\n')
+    return filter(None, map(clean, raw))
+
+
+def disable_python_requires():
+    """
+    On Python 2, install the dependencies that are selective
+    on Python version while honoring REQUIRES_PYTHON, then
+    disable REQUIRES_PYTHON so that pip can install this
+    checkout of setuptools.
+    """
+    pip('install', *test_dependencies())
+    os.environ['PIP_IGNORE_REQUIRES_PYTHON'] = 'true'
+
+
+def run(args):
     if is_install_self(args):
         remove_setuptools()
         bootstrap()
+        sys.version_info > (3,) or disable_python_requires()
 
-    cmd = [sys.executable, '-m', 'pip'] + args
-    subprocess.check_call(cmd)
+    pip(*args)
 
 
 if __name__ == '__main__':
-    pip(sys.argv[1:])
+    run(sys.argv[1:])