Fix intersphinx debug tool

and add automated tests

sphinx/ext/intersphinx.py

@@ -26,6 +26,7 @@
 
 from __future__ import print_function
 
+import sys
 import time
 import zlib
 import codecs
@@ -373,17 +374,26 @@ def setup(app):
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
 
 
-if __name__ == '__main__':
-    # debug functionality to print out an inventory
-    import sys
+def debug(argv):
+    """Debug functionality to print out an inventory"""
+    if len(argv) < 2:
+        print("Print out an inventory file.\n"
+              "Error: must specify local path or URL to an inventory file.",
+              file=sys.stderr)
+        sys.exit(1)
+
+    class MockConfig(object):
+        intersphinx_timeout = None  # type: int
+        tls_verify = False
 
     class MockApp(object):
         srcdir = ''
+        config = MockConfig()
 
         def warn(self, msg):
             print(msg, file=sys.stderr)
 
-    filename = sys.argv[1]
+    filename = argv[1]
     invdata = fetch_inventory(MockApp(), '', filename)
     for key in sorted(invdata or {}):
         print(key)
@@ -391,3 +401,7 @@ if __name__ == '__main__':
             print('\t%-40s %s%s' % (entry,
                                     einfo[3] != '-' and '%-40s: ' % einfo[3] or '',
                                     einfo[2]))
+
+
+if __name__ == '__main__':
+    debug(argv=sys.argv)

tests/test_ext_intersphinx.py

@@ -16,12 +16,16 @@ import zlib
 from six import BytesIO
 from docutils import nodes
 import mock
+import pytest
+import requests
+from io import BytesIO
 
 from sphinx import addnodes
 from sphinx.ext.intersphinx import setup as intersphinx_setup
 from sphinx.ext.intersphinx import read_inventory, \
     load_mappings, missing_reference, _strip_basic_auth, \
-    _get_safe_url, fetch_inventory, INVENTORY_FILENAME
+    _get_safe_url, fetch_inventory, INVENTORY_FILENAME, \
+    debug
 
 
 inventory_v1 = '''\
@@ -282,3 +286,53 @@ def test_getsafeurl_unauthed():
     expected = 'https://domain.com/project/objects.inv'
     actual = _get_safe_url(url)
     assert expected == actual
+
+
+def test_debug_noargs(capsys):
+    """debug interface, without arguments"""
+    with pytest.raises(SystemExit):
+        debug(['sphinx/ext/intersphinx.py'])
+
+    expected = (
+        "Print out an inventory file.\n"
+        "Error: must specify local path or URL to an inventory file."
+    )
+    stdout, stderr = capsys.readouterr()
+    assert stdout == ""
+    assert stderr == expected + "\n"
+
+
+def test_debug_file(capsys, tempdir):
+    """debug interface, with file argument"""
+    inv_file = tempdir / 'inventory'
+    inv_file.write_bytes(inventory_v2)
+
+    debug(['sphinx/ext/intersphinx.py', str(inv_file)])
+
+    stdout, stderr = capsys.readouterr()
+    assert stdout.startswith("c:function\n")
+    assert stderr == ""
+
+
+@mock.patch('requests.get')
+def test_debug_url(fake_get, capsys):
+    """debug interface, with url argument"""
+    raw = BytesIO(inventory_v2)
+    real_read = raw.read
+
+    def fake_read(*args, **kwargs):
+        return real_read()
+
+    raw.read = fake_read
+    url = 'http://hostname/' + INVENTORY_FILENAME
+    resp = requests.Response()
+    resp.status_code = 200
+    resp.url = url
+    resp.raw = raw
+    fake_get.return_value = resp
+
+    debug(['sphinx/ext/intersphinx.py', url])
+
+    stdout, stderr = capsys.readouterr()
+    assert stdout.startswith("c:function\n")
+    assert stderr == ""