Refactor download.get_file_content.

src/pip/_internal/download.py

@@ -636,29 +636,30 @@ def get_file_content(url, comes_from=None, session=None):
             "get_file_content() missing 1 required keyword argument: 'session'"
         )
 
-    match = _scheme_re.search(url)
-    if match:
-        scheme = match.group(1).lower()
-        if (scheme == 'file' and comes_from and
-                comes_from.startswith('http')):
+    scheme = _get_url_scheme(url)
+
+    if scheme in ['http', 'https']:
+        # FIXME: catch some errors
+        resp = session.get(url)
+        resp.raise_for_status()
+        return resp.url, resp.text
+
+    elif scheme == 'file':
+        if comes_from and comes_from.startswith('http'):
             raise InstallationError(
                 'Requirements file %s references URL %s, which is local'
                 % (comes_from, url))
-        if scheme == 'file':
-            path = url.split(':', 1)[1]
-            path = path.replace('\\', '/')
-            match = _url_slash_drive_re.match(path)
-            if match:
-                path = match.group(1) + ':' + path.split('|', 1)[1]
-            path = urllib_parse.unquote(path)
-            if path.startswith('/'):
-                path = '/' + path.lstrip('/')
-            url = path
-        else:
-            # FIXME: catch some errors
-            resp = session.get(url)
-            resp.raise_for_status()
-            return resp.url, resp.text
+
+        path = url.split(':', 1)[1]
+        path = path.replace('\\', '/')
+        match = _url_slash_drive_re.match(path)
+        if match:
+            path = match.group(1) + ':' + path.split('|', 1)[1]
+        path = urllib_parse.unquote(path)
+        if path.startswith('/'):
+            path = '/' + path.lstrip('/')
+        url = path
+
     try:
         with open(url, 'rb') as f:
             content = auto_decode(f.read())
@@ -669,16 +670,22 @@ def get_file_content(url, comes_from=None, session=None):
     return url, content
 
 
-_scheme_re = re.compile(r'^(http|https|file):', re.I)
 _url_slash_drive_re = re.compile(r'/*([a-z])\|', re.I)
 
 
+def _get_url_scheme(url):
+    # type: (Union[str, Text]) -> Optional[Text]
+    if ':' not in url:
+        return None
+    return url.split(':', 1)[0].lower()
+
+
 def is_url(name):
     # type: (Union[str, Text]) -> bool
     """Returns true if the name looks like a URL"""
-    if ':' not in name:
+    scheme = _get_url_scheme(name)
+    if scheme is None:
         return False
-    scheme = name.split(':', 1)[0].lower()
     return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes
 
 

tests/unit/test_download.py

@@ -16,6 +16,7 @@ from pip._internal.download import (
     PipSession,
     SafeFileCache,
     _download_http_url,
+    _get_url_scheme,
     parse_content_disposition,
     sanitize_content_filename,
     unpack_file_url,
@@ -291,6 +292,16 @@ def test_download_http_url__no_directory_traversal(tmpdir):
     assert actual == ['out_dir_file']
 
 
+@pytest.mark.parametrize("url,expected", [
+    ('http://localhost:8080/', 'http'),
+    ('file:c:/path/to/file', 'file'),
+    ('file:/dev/null', 'file'),
+    ('', None),
+])
+def test__get_url_scheme(url, expected):
+    assert _get_url_scheme(url) == expected
+
+
 @pytest.mark.parametrize("url,win_expected,non_win_expected", [
     ('file:tmp', 'tmp', 'tmp'),
     ('file:c:/path/to/file', r'C:\path\to\file', 'c:/path/to/file'),