🔗 get_relative_path

Author: chriddyp

dash/_utils.py

@@ -54,6 +54,18 @@ def get_asset_path(requests_pathname, asset_path, asset_url_path):
     )
 
 
+
+def get_relative_path(requests_pathname, path):
+
+    return "/".join(
+        [
+            # Only take the first part of the pathname
+            requests_pathname.rstrip("/"),
+            path
+        ]
+    )
+
+
 # pylint: disable=no-member
 def patch_collections_abc(member):
     return getattr(collections if utils.PY2 else collections.abc, member)

dash/dash.py

@@ -35,6 +35,7 @@
 from ._utils import patch_collections_abc as _patch_collections_abc
 from . import _watch
 from ._utils import get_asset_path as _get_asset_path
+from ._utils import get_relative_path as _get_relative_path
 from ._utils import create_callback_id as _create_callback_id
 from ._configs import get_combined_config, pathname_configs
 from .version import __version__
@@ -1357,7 +1358,7 @@ def add_context(*args, **kwargs):
                     has_update = False
                     for i, o in enumerate(output):
                         val = output_value[i]
-                        if not isinstance(val, _NoUpdate):
+                        if val is not no_update:
                             has_update = True
                             o_id, o_prop = o.component_id, o.component_property
                             component_ids[o_id][o_prop] = val
@@ -1367,7 +1368,7 @@ def add_context(*args, **kwargs):
 
                     response = {"response": component_ids, "multi": True}
                 else:
-                    if isinstance(output_value, _NoUpdate):
+                    if output_value is no_update:
                         raise exceptions.PreventUpdate
 
                     response = {
@@ -1565,6 +1566,33 @@ def get_asset_url(self, path):
 
         return asset
 
+    def get_relative_path(self, path):
+        """
+        Return a path with `requests_pathname_prefix` prefixed before it.
+
+        Use this function when specifying local URL paths that will work
+        in environments regardless of what `requests_pathname_prefix` is.
+
+        In some deployment environments, like Dash Enterprise,
+        `requests_pathname_prefix` is set to the application name,
+        e.g. `my-dash-app`.
+
+        When working locally, `requests_pathname_prefix` might be unset and
+        so a relative URL like `/page-2` can just be `/page-2`.
+
+        However, when the app is deployed to a URL like `/my-dash-app`, then
+        `app.get_relative_path('/page-2')` will return `/my-dash-app/page-2`.
+
+        This can be used as an alternative to `get_asset_url` as well with
+        `app.get_relative_path('/assets/logo.png')`
+        """
+        asset = _get_relative_path(
+            self.config.requests_pathname_prefix,
+            path,
+        )
+
+        return asset
+
     def _setup_dev_tools(self, **kwargs):
         debug = kwargs.get("debug", False)
         dev_tools = self._dev_tools = _AttributeDict()

tests/unit/test_configs.py

@@ -12,7 +12,10 @@
     get_combined_config,
     load_dash_env_vars,
 )
-from dash._utils import get_asset_path
+from dash._utils import (
+    get_asset_path,
+    get_relative_path,
+)
 
 
 @pytest.fixture
@@ -156,3 +159,27 @@ def test_load_dash_env_vars_refects_to_os_environ(empty_environ):
 def test_app_name_server(empty_environ, name, server, expected):
     app = Dash(name=name, server=server)
     assert app.config.name == expected
+
+
+@pytest.mark.parametrize(
+    "prefix, partial_path, expected",
+    [
+        ("/", "/", "/"),
+        ("/my-dash-app", "/", "/my-dash-app/"),
+
+        ("/", "/page-1", "/page-1"),
+        ("/my-dash-app", "/page-1", "/my-dash-app/page-1"),
+
+        ("/", "/page-1/", "/page-1/"),
+        ("/my-dash-app", "/page-1/", "/my-dash-app/page-1/"),
+
+        ("/", "/page-1/sub-page-1", "/page-1/sub-page-1"),
+        ("/my-dash-app", "/page-1/sub-page-1", "/my-dash-app/page-1/sub-page-1"),
+
+        ("/", "relative-page-1", "relative-page-1"),
+        ("/my-dash-app", "/my-dash-apprelative-page-1", "/my-dash-apprelative-page-1"),
+    ],
+)
+def test_pathname_prefix_relative_url(prefix, partial_path, expected):
+    path = get_relative_path(prefix, partial_path)
+    assert path == expected