Make pip install -e uninstall existing versions

CHANGES.txt

@@ -1,5 +1,8 @@
 **8.2.0 (unreleased)**
 
+* Uninstall existing packages when performing an editable installation of
+  the same packages (:issue:`1548`).
+
 * Pip show is less verbose by default. `--verbose` prints multiline fields
 
 * Added optional column formatting to ``pip list`` (:issue:`3651`).

pip/req/req_install.py

@@ -1000,6 +1000,12 @@ def check_if_exists(self):
             no_marker = Requirement(str(self.req))
             no_marker.marker = None
             self.satisfied_by = pkg_resources.get_distribution(str(no_marker))
+            if self.editable and self.satisfied_by:
+                self.conflicts_with = self.satisfied_by
+                # when installing editables, nothing pre-existing should ever
+                # satisfy
+                self.satisfied_by = None
+                return True
         except pkg_resources.DistributionNotFound:
             return False
         except pkg_resources.VersionConflict:

pip/req/req_set.py

@@ -489,6 +489,7 @@ def _prepare_file(self,
                 abstract_dist.prep_for_dist()
                 if self.is_download:
                     req_to_install.archive(self.download_dir)
+                req_to_install.check_if_exists()
             elif req_to_install.satisfied_by:
                 if require_hashes:
                     logger.debug(

tests/functional/test_install.py

@@ -179,6 +179,56 @@ def test_install_editable_from_git_autobuild_wheel(script, tmpdir):
     _test_install_editable_from_git(script, tmpdir, True)
 
 
+def test_install_editable_uninstalls_existing(data, script, tmpdir):
+    """
+    Test that installing an editable uninstalls a previously installed
+    non-editable version.
+    https://github.com/pypa/pip/issues/1548
+    https://github.com/pypa/pip/pull/1552
+    """
+    to_install = data.packages.join("pip-test-package-0.1.tar.gz")
+    result = script.pip_install_local(to_install)
+    assert 'Successfully installed pip-test-package' in result.stdout
+    result.assert_installed('piptestpackage', editable=False)
+
+    result = script.pip(
+        'install', '-e',
+        '%s#egg=pip-test-package' %
+        local_checkout(
+            'git+http://github.com/pypa/pip-test-package.git',
+            tmpdir.join("cache"),
+        ),
+    )
+    result.assert_installed('pip-test-package', with_files=['.git'])
+    assert 'Found existing installation: pip-test-package 0.1' in result.stdout
+    assert 'Uninstalling pip-test-package-' in result.stdout
+    assert 'Successfully uninstalled pip-test-package' in result.stdout
+
+
+def test_install_editable_uninstalls_existing_from_path(script, data):
+    """
+    Test that installing an editable uninstalls a previously installed
+    non-editable version from path
+    """
+    to_install = data.src.join('simplewheel-1.0')
+    result = script.pip_install_local(to_install)
+    assert 'Successfully installed simplewheel' in result.stdout
+    simple_folder = script.site_packages / 'simple'
+    result.assert_installed('simple', editable=False)
+    assert simple_folder in result.files_created, str(result.stdout)
+
+    result = script.pip(
+        'install', '-e',
+        to_install,
+    )
+    install_path = script.site_packages / 'simplewheel.egg-link'
+    assert install_path in result.files_created, str(result)
+    assert 'Found existing installation: simplewheel 1.0' in result.stdout
+    assert 'Uninstalling simplewheel-' in result.stdout
+    assert 'Successfully uninstalled simplewheel' in result.stdout
+    assert simple_folder in result.files_deleted, str(result.stdout)
+
+
 def test_install_editable_from_hg(script, tmpdir):
     """Test cloning from Mercurial."""
     pkg_path = _create_test_package(script, name='testpackage', vcs='hg')