Factor out editable parsing into a function

src/pip/_internal/req/constructors.py

@@ -28,7 +28,6 @@ from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.filetypes import ARCHIVE_EXTENSIONS
 from pip._internal.utils.misc import is_installable_dir, path_to_url, splitext
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
-from pip._internal.utils.urls import url_to_path
 from pip._internal.vcs import is_url, vcs
 from pip._internal.wheel import Wheel
 
@@ -179,6 +178,23 @@ def deduce_helpful_msg(req):
     return msg
 
 
+def parse_req_from_editable(editable_req):
+    # type: (str) -> RequirementParts
+    name, url, extras_override = parse_editable(editable_req)
+
+    if name is not None:
+        try:
+            req = Requirement(name)
+        except InvalidRequirement:
+            raise InstallationError("Invalid requirement: '%s'" % name)
+    else:
+        req = None
+
+    link = Link(url)
+
+    return RequirementParts(req, link, None, extras_override)
+
+
 # ---- The actual constructors follow ----
 
 
@@ -192,23 +208,8 @@ def install_req_from_editable(
     constraint=False  # type: bool
 ):
     # type: (...) -> InstallRequirement
-    name, url, extras_override = parse_editable(editable_req)
-    if url.startswith('file:'):
-        source_dir = url_to_path(url)
-    else:
-        source_dir = None
 
-    if name is not None:
-        try:
-            req = Requirement(name)
-        except InvalidRequirement:
-            raise InstallationError("Invalid requirement: '%s'" % name)
-    else:
-        req = None
-
-    link = Link(url)
-
-    parts = RequirementParts(req, link, None, extras_override)
+    parts = parse_req_from_editable(editable_req)
 
     source_dir = parts.link.file_path if parts.link.scheme == 'file' else None