strip the ending slash for static_url_path

CHANGES.rst

@@ -7,6 +7,8 @@ Unreleased
 
 -   Work around an issue when running the ``flask`` command with an
     external debugger on Windows. :issue:`3297`
+-   The static route will not catch all URLs if the ``Flask``
+    ``static_folder`` argument ends with a slash. :issue:`3452`
 
 
 Version 1.1.1

src/flask/helpers.py

@@ -1013,7 +1013,7 @@ class _PackageBoundObject(object):
             return self._static_url_path
 
         if self.static_folder is not None:
-            basename = os.path.basename(self.static_folder)
+            basename = os.path.basename(self.static_folder.rstrip("/"))
             return ("/" + basename).rstrip("/")
 
     @static_url_path.setter

tests/test_basic.py

@@ -1425,6 +1425,17 @@ def test_static_url_empty_path_default(app):
     rv.close()
 
 
+def test_static_folder_with_ending_slash():
+    app = flask.Flask(__name__, static_folder="static/")
+
+    @app.route("/<path:path>")
+    def catch_all(path):
+        return path
+
+    rv = app.test_client().get("/catch/all")
+    assert rv.data == b"catch/all"
+
+
 def test_static_route_with_host_matching():
     app = flask.Flask(__name__, host_matching=True, static_host="example.com")
     c = app.test_client()