ignore colon with slash when split app_import_path

Flask currently supports importing app through a combination of module
path and app variable name, such as '/usr/app.py:my_app'. When the
module path contains a colon, it will conflict with this import way and
a `flask.cli.NoAppException` will be raised.

A file path on a Windows system may contain a colon followed by a slash.
So we solved this problem on Windows by ignoring the colon followed by a
slash when we split app_import_path.

Fix issue #2961.

flask/cli.py

@@ -369,7 +369,7 @@ class ScriptInfo(object):
             app = call_factory(self, self.create_app)
         else:
             if self.app_import_path:
-                path, name = (self.app_import_path.split(':', 1) + [None])[:2]
+                path, name = (re.split(r':(?![\\/])', self.app_import_path, 1) + [None])[:2]
                 import_name = prepare_import(path)
                 app = locate_app(self, import_name, name)
             else:

tests/test_cli.py

@@ -261,8 +261,21 @@ def test_get_version(test_apps, capsys):
 def test_scriptinfo(test_apps, monkeypatch):
     """Test of ScriptInfo."""
     obj = ScriptInfo(app_import_path="cliapp.app:testapp")
-    assert obj.load_app().name == "testapp"
+    app = obj.load_app()
-    assert obj.load_app().name == "testapp"
+    assert app.name == "testapp"
+    assert obj.load_app() is app
+
+    # import app with module's absolute path
+    cli_app_path = os.path.abspath(os.path.join(
+            os.path.dirname(__file__), 'test_apps', 'cliapp', 'app.py'))
+    obj = ScriptInfo(app_import_path=cli_app_path)
+    app = obj.load_app()
+    assert app.name == 'testapp'
+    assert obj.load_app() is app
+    obj = ScriptInfo(app_import_path=cli_app_path + ':testapp')
+    app = obj.load_app()
+    assert app.name == 'testapp'
+    assert obj.load_app() is app
 
     def create_app(info):
         return Flask("createapp")
@@ -270,7 +283,7 @@ def test_scriptinfo(test_apps, monkeypatch):
     obj = ScriptInfo(create_app=create_app)
     app = obj.load_app()
     assert app.name == "createapp"
-    assert obj.load_app() == app
+    assert obj.load_app() is app
 
     obj = ScriptInfo()
     pytest.raises(NoAppException, obj.load_app)