(v2) Fix build of OpenAPI Console UI URL if servers/url is missing or "/"

Fixes #2093

Changes proposed in this pull request:
- Use "/" if the escaped app base path is the empty string, to adjust for
  new behavior of Flask and/or Werkzeug, which raises this error if the
  swagger.yaml file has no servers/url entry or servers/url with value "/":

  werkzeug.routing.exceptions.BuildError: Could not build url for endpoint '/._openapi_json'.

- Add new test case to check blueprint and url prefix of open API specification
  with servers/url value "/"

- Add new test case to confirm Swagger UI is returned when the specification
  (either OpenAPI or Swagger) has a trivial base path

Author: chrisinmtown

connexion/apis/flask_api.py

@@ -323,7 +323,7 @@ def console_ui_home(self):
         :return:
         """
         openapi_json_route_name = "{blueprint}.{prefix}_openapi_json"
-        escaped = flask_utils.flaskify_endpoint(self.base_path)
+        escaped = flask_utils.flaskify_endpoint(self.base_path) or "/"
         openapi_json_route_name = openapi_json_route_name.format(
             blueprint=escaped, prefix=escaped
         )

tests/api/test_bootstrap.py

@@ -98,6 +98,16 @@ def test_swagger_ui(simple_api_spec_dir, spec):
         assert b"swagger-ui-config.json" not in swagger_ui.data
 
 
+@pytest.mark.parametrize("spec", ["basepath-slash.yaml", "servers-url-slash.yaml"])
+def test_swagger_ui_for_basepath_slash(simple_api_spec_dir, spec):
+    """Verify the Swagger UI is returned when spec has trivial base path."""
+    app = App(__name__, port=5001, specification_dir=simple_api_spec_dir, debug=True)
+    app.add_api(spec)
+    app_client = app.app.test_client()
+    swagger_ui = app_client.get("/ui/")  # type: flask.Response
+    assert swagger_ui.status_code == 200
+
+
 @pytest.mark.parametrize("spec", SPECS)
 def test_swagger_ui_with_config(simple_api_spec_dir, spec):
     swagger_ui_config = {"displayOperationId": True}

tests/fixtures/simple/servers-url-slash.yaml

@@ -0,0 +1,28 @@
+openapi: 3.0.0
+info:
+  title: "Test servers/url == /"
+  version: '1.0'
+
+servers:
+  - url: /
+
+paths:
+  '/greeting/{name}':
+    post:
+      summary: Generate greeting
+      description: Generates a greeting message.
+      operationId: fakeapi.hello.post_greeting
+      responses:
+        '200':
+          description: greeting response
+          content:
+            'application/json':
+              schema:
+                type: object
+      parameters:
+        - name: name
+          in: path
+          description: Name of the person to greet.
+          required: true
+          schema:
+            type: string

tests/test_api.py

@@ -42,6 +42,10 @@ def test_api_base_path_slash():
     assert api.blueprint.name == "/"
     assert api.blueprint.url_prefix == ""
 
+    api2 = FlaskApi(TEST_FOLDER / "fixtures/simple/servers-url-slash.yaml")
+    assert api2.blueprint.name == "/"
+    assert api2.blueprint.url_prefix == ""
+
 
 def test_template():
     api1 = FlaskApi(

tox.ini

@@ -1,3 +1,14 @@
+# Run all tests:
+#   tox
+# Run all tests in one file in all test environments:
+#   tox -- tests/test_api.py
+# Run one test in all test environments:
+#   tox -- tests/test_api.py::test_api
+# Run all tests in one file in one test environment:
+#   tox -e py39 -- tests/test_api.py
+# Run one test in one test environment:
+#   tox -e py39 -- tests/test_api.py::test_api
+
 [flake8]
 exclude=connexion/__init__.py
 rst-roles=class,mod,obj
@@ -9,18 +20,21 @@ extend-ignore=E203,RST303
 [tox]
 isolated_build = True
 envlist =
-    {py39,py310,py311,py312}-pypi
+    py38-min
+    {py38,py39,py310,py311,py312}-pypi
     pre-commit
-    # min test modifies pyproject.toml so run it last
-    py39-min
 
 [gh-actions]
 python =
-    3.9: py39-min,py39-pypi
+    3.8: py38-min,py38-pypi
+    3.9: py39-pypi
     3.10: py310-pypi
     3.11: py311-pypi,pre-commit
     3.12: py312-pypi
 
+[pytest]
+testpaths = tests
+
 [testenv]
 setenv=PYTHONPATH = {toxinidir}:{toxinidir}
 deps=
@@ -34,7 +48,7 @@ commands=
     poetry lock
     poetry install --all-extras --with tests
     poetry show
-    poetry run python -m pytest tests --cov connexion --cov-report term-missing
+    poetry run python -m pytest --cov connexion --cov-report term-missing {posargs}
     min: mv -f pyproject.toml.bak pyproject.toml
 
 [testenv:pre-commit]