PR feedback and tests

src/pip/_internal/req/constructors.py

@@ -335,6 +335,8 @@ def install_req_from_req_string(
         )
 
     if req.url:
+        # Create an InstallRequirement for a PEP 508 URL with the same behavior
+        # as 'pip install req.url'
         return install_req_from_line(
             req.url, comes_from=comes_from, isolated=isolated,
             wheel_cache=wheel_cache, use_pep517=use_pep517

tests/functional/test_install.py

@@ -1391,17 +1391,25 @@ def test_install_pep508_with_url_in_install_requires(script):
     assert "Successfully installed packaging-15.3" in str(res), str(res)
 
 
-def test_install_pep508_with_url_in_install_requires_url_change(script):
-    dep_v1_path = create_basic_wheel_for_package(
-        script, name='dep', version='1.0',
-    )
-    dep_v2_path = create_basic_wheel_for_package(
-        script, name='dep', version='2.0',
-    )
+@pytest.mark.parametrize('create_dep, format', [
+    (create_test_package_with_setup, 'directory'),
+    (create_basic_wheel_for_package, 'wheel'),
+])
+def test_install_pep508_with_url_in_install_requires_url_change(
+        create_dep, format, script):
+    dep_v1_path = create_dep(script, name='dep', version='1.0')
+
+    if format == 'directory':
+        # Rename the package directory so it doesn't get overwritten when
+        # creating the package for dep_v2
+        dep_v1_path.move(dep_v1_path.folder / 'dep_v1')
+        dep_v1_path = dep_v1_path.folder / 'dep_v1'
+
+    dep_v2_path = create_dep(script, name='dep', version='2.0')
 
     pkga_path = create_basic_wheel_for_package(
         script, name='pkga', version='1.0',
-        depends=['dep @ file://%s' % dep_v1_path],
+        depends=['dep @ ' + path_to_url(dep_v1_path)],
     )
     res = script.pip('install', pkga_path)
     assert "Successfully installed dep-1.0" in str(res), str(res)
@@ -1411,14 +1419,20 @@ def test_install_pep508_with_url_in_install_requires_url_change(script):
     # Updating the URL to the dependency installs the updated dependency
     pkga_path = create_basic_wheel_for_package(
         script, name='pkga', version='2.0',
-        depends=['dep @ file://%s' % dep_v2_path],
+        depends=['dep @ ' + path_to_url(dep_v2_path)],
     )
     res = script.pip('install', pkga_path)
     assert "Successfully installed dep-2.0" in str(res), str(res)
 
-    # The dependency is not reinstalled if the URL doesn't change
     res = script.pip('install', pkga_path)
-    assert "Requirement already satisfied: dep==2.0" in str(res), str(res)
+    if format == 'directory':
+        # pip can't determine versions from a directory name, so it will always
+        # reinstall the dependency
+        assert "Successfully installed dep-2.0" in str(res), str(res)
+    else:
+        # pip can determine the version from a wheel's filename, so the
+        # dependency is not reinstalled if the URL doesn't change
+        assert "Requirement already satisfied: dep==2.0" in str(res), str(res)
 
 
 @pytest.mark.network

tests/unit/test_req_install.py

@@ -5,7 +5,7 @@
 from pip._vendor.packaging.requirements import Requirement
 
 from pip._internal.req.constructors import (
-    install_req_from_line, install_req_from_req_string,
+    install_req_from_line, install_req_from_req_string, path_to_url,
 )
 from pip._internal.req.req_install import InstallRequirement
 
@@ -92,3 +92,41 @@ def test_install_req_from_string_with_comes_from_without_link(self):
         assert install_req.link.url == wheel_url
         assert install_req.req.url is None
         assert install_req.is_wheel
+
+    @pytest.mark.parametrize("use_pep517", [None, True, False])
+    def test_install_req_from_string_pep508_url_wheel(self, use_pep517):
+        """
+        install_req_from_string parses the version from PEP 508 URLs that point
+        to wheels so that updating the URL reinstalls the package.
+        """
+        wheel_url = ("https://download.pytorch.org/whl/cu90/"
+                     "torch-1.0.0-cp36-cp36m-win_amd64.whl")
+        install_str = "torch@ " + wheel_url
+        install_req = install_req_from_req_string(
+            install_str, use_pep517=use_pep517
+        )
+
+        assert isinstance(install_req, InstallRequirement)
+        assert str(install_req.req) == "torch==1.0.0"
+        assert install_req.link.url == wheel_url
+        assert install_req.is_wheel
+        assert install_req.use_pep517 == use_pep517
+
+    @pytest.mark.parametrize("use_pep517", [None, True, False])
+    def test_install_req_from_string_pep508_url_not_a_wheel(
+            self, use_pep517, tmpdir):
+        """
+        install_req_from_string returns an InstallRequirement() with
+        ``.req = None`` so that the package is always reinstalled.
+        """
+        file_url = path_to_url(tmpdir / "fake_torch_package")
+        install_str = "torch@ " + file_url
+        install_req = install_req_from_req_string(
+            install_str, use_pep517=use_pep517
+        )
+
+        assert isinstance(install_req, InstallRequirement)
+        assert install_req.req is None
+        assert install_req.link.url == file_url
+        assert not install_req.is_wheel
+        assert install_req.use_pep517 == use_pep517