use append_slash=False on add_route to specify no trailing slash

CHANGES.rst

@@ -14,9 +14,10 @@ Features
 
 - It is now possible to declare a route to not contain a trailing slash
   when it is mounted via ``config.include(..., route_prefix=...)`` or via
-  ``with config.route_prefix_context(...)`` by specifying a ``pattern`` of
-  ``''``. This change is backward incompatible, see the notes below.
-  See https://github.com/Pylons/pyramid/pull/3414
+  ``with config.route_prefix_context(...)`` by specifying
+  ``append_slash=False`` when adding a route with an empty pattern. For
+  example, ``config.add_route(name, '/', append_slash=False, ...)``.
+  See https://github.com/Pylons/pyramid/pull/3420
 
 Bug Fixes
 ---------
@@ -74,15 +75,6 @@ Backward Incompatibilities
   documentation for more information about why this change was made.
   See https://github.com/Pylons/pyramid/pull/3413
 
-- Changed the URL generation and matching for a route with a ``pattern`` of
-  ``''`` when the route is mounted with a ``route_prefix`` via either
-  ``config.include(..., route_prefix=...)`` or
-  ``with config.route_prefix_context(...)``. This route will now match a bare
-  URL without a trailing slash. To preserve the old behavior, set the
-  ``pattern`` to ``'/'`` instead of the empty string and the URL will contain
-  a trailing slash. This only affects mounted routes using ``route_prefix``.
-  See https://github.com/Pylons/pyramid/pull/3414
-
 Documentation Changes
 ---------------------
 

docs/glossary.rst

@@ -1203,3 +1203,7 @@ Glossary
        A media type is a nested structure containing a top-level type and a subtype.
        Optionally, a media type can also contain parameters specific to the type.
        See :rfc:`6838` for more information about media types.
+
+   route prefix
+      A route prefix is a path prefix that is prepended to any routes that are configured while it is active.
+      A route prefix can be set via :meth:`pyramid.config.Configurator.include` or :meth:`pyramid.config.Configurator.route_prefix_context`.

docs/narr/urldispatch.rst

@@ -971,7 +971,7 @@ application from small and potentially reusable components.
 The :meth:`pyramid.config.Configurator.include` method accepts an argument
 named ``route_prefix`` which can be useful to authors of URL-dispatch-based
 applications.  If ``route_prefix`` is supplied to the include method, it must
-be a string.  This string represents a route prefix that will be prepended to
+be a string.  This string represents a :term:`route prefix` that will be prepended to
 all route patterns added by the *included* configuration.  Any calls to
 :meth:`pyramid.config.Configurator.add_route` within the included callable will
 have their pattern prefixed with the value of ``route_prefix``. This can be
@@ -998,23 +998,21 @@ then only match if the URL path is ``/users/show``, and when the
 :meth:`pyramid.request.Request.route_url` function is called with the route
 name ``show_users``, it will generate a URL with that same path.
 
-To create a prefixed route that matches requests to the ``route_prefix``
-without a trailing slash set the route ``pattern`` to an empty string.
+To create a route that matches requests to the ``route_prefix`` without a trailing slash, pass ``append_slash=False`` to the call to ``add_route``.
 
 .. code-block:: python
    :linenos:
 
    from pyramid.config import Configurator
 
    def users_include(config):
-       config.add_route('show_users', '')
+       config.add_route('show_users', '', append_slash=False)
 
    def main(global_config, **settings):
        config = Configurator()
        config.include(users_include, route_prefix='/users')
 
-The above configuration will match ``/users`` instead of ``/users/`` if a slash
-had been supplied to the :meth:`pyramid.config.Configurator.add_route` function.
+The above configuration will match ``/users`` instead of ``/users/``.
 
 Route prefixes are recursive, so if a callable executed via an include itself
 turns around and includes another callable, the second-level route prefix will

src/pyramid/config/__init__.py

@@ -602,7 +602,9 @@ def main(global_config, **settings):
         configuration conflict by registering something with the same
         configuration parameters.
 
-        If the ``route_prefix`` is supplied, it must be a string.  Any calls
+        If the ``route_prefix`` is supplied, it must be a string and will
+        have a similar effect to using
+        :meth:`pyramid.config.Configurator.route_prefix_context`.  Any calls
         to :meth:`pyramid.config.Configurator.add_route` within the included
         callable will have their pattern prefixed with the value of
         ``route_prefix``. This can be used to help mount a set of routes at a

src/pyramid/config/routes.py

@@ -40,6 +40,7 @@ def add_route(
         path=None,
         pregenerator=None,
         static=False,
+        append_slash=None,
         **predicates
     ):
         """ Add a :term:`route configuration` to the current
@@ -139,6 +140,20 @@ def add_route(
 
           .. versionadded:: 1.1
 
+        append_slash
+
+          This argument is normally ``None`` and only has an effect when
+          adding the route with an active :term:`route prefix` and the pattern
+          is ``''`` or ``'/'``. By default, a slash (``/``) is always appended
+          to the route such that if the ``route_prefix='/users'``, the
+          resulting route pattern would be ``/users/``. Sometimes this behavior
+          is not necessary, and a pattern without a trailing slash is
+          preferred. In these cases, ``append_slash=False`` may be supplied
+          such that when a route prefix is active, the resulting route pattern
+          would be ``/users``..
+
+          .. versionadded:: 2.0
+
         Predicate Arguments
 
         pattern
@@ -364,10 +379,14 @@ def external_url_pregenerator(request, elements, kw):
             static = True
 
         elif self.route_prefix:
-            if pattern == '':
+            if (pattern == '' or pattern == '/') and (
+                append_slash is not None and not append_slash
+            ):
                 pattern = self.route_prefix.rstrip('/')
             else:
-                pattern = self.route_prefix.rstrip('/') + '/' + pattern.lstrip('/')
+                pattern = (
+                    self.route_prefix.rstrip('/') + '/' + pattern.lstrip('/')
+                )
 
         mapper = self.get_routes_mapper()
 
@@ -517,9 +536,8 @@ def get_routes_mapper(self):
 
     @contextlib.contextmanager
     def route_prefix_context(self, route_prefix):
-        """ Return this configurator with the
-        :attr:`pyramid.config.Configurator.route_prefix` attribute mutated to
-        include the new ``route_prefix``.
+        """
+        Return this configurator with a :term:`route prefix` temporarily set.
 
         When the context exits, the ``route_prefix`` is reset to the original.
 

tests/test_config/test_routes.py

@@ -54,10 +54,10 @@ def test_add_route_with_route_prefix(self):
         config.add_route('name', 'path')
         self._assertRoute(config, 'name', 'root/path')
 
-    def test_add_route_with_empty_string_with_route_prefix(self):
+    def test_add_route_with_route_prefix_with_append_slash_False(self):
         config = self._makeOne(autocommit=True)
         config.route_prefix = 'root'
-        config.add_route('name', '')
+        config.add_route('name', '', append_slash=False)
         self._assertRoute(config, 'name', 'root')
 
     def test_add_route_with_root_slash_with_route_prefix(self):