[issue 1548] Make pip install -e uninstall existing versions

pip/req/req_install.py

@@ -876,6 +876,13 @@ def check_if_exists(self):
                 return True
             else:
                 self.satisfied_by = pkg_resources.get_distribution(self.req)
+
+            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

@@ -217,7 +217,7 @@ def prepare_files(self, finder, force_root_egg_info=False, bundle=False):
             ## Search for archive to fulfill requirement ##
             ###############################################
 
-            if not self.ignore_installed and not req_to_install.editable:
+            if not self.ignore_installed:
                 req_to_install.check_if_exists()
                 if req_to_install.satisfied_by:
                     if self.upgrade:

tests/functional/test_install.py

@@ -228,6 +228,32 @@ def test_install_editable_from_git(script, tmpdir):
     result.assert_installed('pip-test-package', with_files=['.git'])
 
 
+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_from_hg(script, tmpdir):
     """
     Test cloning from Mercurial.