Fix handling of trailing slash to match API Gateway

API Gateway will not match a URI against a route that has a capture
group as the last path component if that capture group would be filled
with an empty string. Example:

With the route:
/resource/{name}

/resource/bob matches
/resource/    does not match

Previously local mode would match both URIs to that route, setting the
name parameter to an empty string.

closes aws#582

This change also prvents `chalice local` from running if there is a
route that ends with a / since `chalice deploy` will not let you deploy
such routes.

CHANGELOG.rst

@@ -2,6 +2,13 @@
 CHANGELOG
 =========
 
+
+Next Release (TBD)
+==================
+* Fix local mode handling of routes with trailing slashes
+   (`#582 <https://github.com/aws/chalice/issues/582>`__)
+
+
 1.0.4
 =====
 

chalice/cli/__init__.py

@@ -23,6 +23,7 @@
 from chalice.utils import record_deployed_values
 from chalice.utils import remove_stage_from_deployed_values
 from chalice.deploy.deployer import validate_python_version
+from chalice.deploy.deployer import validate_routes
 from chalice.utils import getting_started_prompt, UI, serialize_to_json
 from chalice.constants import CONFIG_VERSION, TEMPLATE_APP, GITIGNORE
 from chalice.constants import DEFAULT_STAGE_NAME
@@ -94,6 +95,10 @@ def run_local_server(factory, port, stage, env):
     # app.
     env.update(config.environment_variables)
     app_obj = factory.load_chalice_app()
+    # Check that `chalice deploy` would let us deploy these routes, otherwise
+    # there is no point in testing locally.
+    routes = config.chalice_app.routes
+    validate_routes(routes)
     # When running `chalice local`, a stdout logger is configured
     # so you'll see the same stdout logging as you would when
     # running in lambda.  This is configuring the root logger.

chalice/local.py

@@ -123,7 +123,12 @@ def match_route(self, url):
         # Otherwise we need to check for param substitution
         parsed_url = urlparse(url)
         query_params = {k: v[0] for k, v in parse_qs(parsed_url.query).items()}
-        parts = parsed_url.path.split('/')
+        path = parsed_url.path
+        # API Gateway removes the trailing slash if the route is not the root
+        # path. We do the same here so our route matching works the same way.
+        if path != '/' and path.endswith('/'):
+            path = path[:-1]
+        parts = path.split('/')
         captured = {}
         for route_url in self.route_urls:
             url_parts = route_url.split('/')

tests/unit/cli/test_cli.py

@@ -1,4 +1,5 @@
 import mock
+import pytest
 
 from chalice import cli
 from chalice.cli.factory import CLIFactory
@@ -12,10 +13,25 @@ def test_run_local_server():
     factory.create_config_obj.return_value.environment_variables = {
         'foo': 'bar',
     }
+    factory.create_config_obj.return_value.chalice_app.routes = {}
     local_server = mock.Mock(spec=LocalDevServer)
     factory.create_local_server.return_value = local_server
     cli.run_local_server(factory, 8000, local_stage_test, env)
     assert env['foo'] == 'bar'
     local_server.serve_forever.assert_called_with()
     factory.create_config_obj.assert_called_with(
         chalice_stage_name=local_stage_test)
+
+
+def test_cannot_run_local_mode_with_trailing_slash_route():
+    local_stage_test = 'local_test'
+    factory = mock.Mock(spec=CLIFactory)
+    factory.create_config_obj.return_value.environment_variables = {}
+    factory.create_config_obj.return_value.chalice_app.routes = {
+        'foobar/': None
+    }
+    local_server = mock.Mock(spec=LocalDevServer)
+    factory.create_local_server.return_value = local_server
+    with pytest.raises(ValueError) as e:
+        cli.run_local_server(factory, 8000, local_stage_test, {})
+    assert str(e.value) == 'Route cannot end with a trailing slash: foobar/'

tests/unit/test_local.py

@@ -486,6 +486,8 @@ def test_can_deny_unauthed_request(auth_handler):
     ('/foo/other', '/foo/{capture}'),
     ('/names/foo', '/names/{capture}'),
     ('/names/bar', '/names/{capture}'),
+    ('/names/bar/', '/names/{capture}'),
+    ('/names/', None),
     ('/nomatch', None),
     ('/names/bar/wrong', None),
     ('/a/z/c', '/a/{capture}/c'),