web_server: Introduce component to handle special static file dirs

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

doc/dev/reference/components/index.rst

@@ -14,6 +14,7 @@ Components
    frontpage
    domain
    letsencrypt
+   staticfiles
 
 Base Classes
 ^^^^^^^^^^^^

doc/dev/reference/components/staticfiles.rst

@@ -0,0 +1,7 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+StaticFiles
+^^^^^^^^^^^
+
+.. autoclass:: plinth.web_server.StaticFiles
+   :members:

plinth/tests/test_web_server.py

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""
+Tests for CherryPy web server setup and its components.
+"""
+
+from unittest.mock import call, patch
+
+import pytest
+
+from plinth.web_server import StaticFiles
+
+
+@pytest.fixture(autouse=True)
+def fixture_cleanup_static_files():
+    """Ensure that global list of static files is clean."""
+    StaticFiles._all_instances = {}
+
+
+def test_static_files_init():
+    """Test that static files component is being initialized correctly."""
+    component = StaticFiles('test-component')
+    assert component.component_id == 'test-component'
+    assert component.directory_map is None
+
+    directory_map = {'/a': '/b'}
+    component = StaticFiles('test-component', directory_map)
+    assert component.directory_map == directory_map
+
+
+def test_static_files_list():
+    """Test that static files components can be listed properly."""
+    component1 = StaticFiles('test-component1')
+    component2 = StaticFiles('test-component2')
+
+    assert set(StaticFiles.list()) == {component1, component2}
+
+
+@patch('cherrypy.tree.mount')
+def test_static_files_mount(mount, load_cfg):
+    """Test that mounting on CherryPy works as expected."""
+    directory_map = {'/a': '/b', '/c': '/d'}
+    component = StaticFiles('test-component', directory_map)
+    component.mount()
+
+    calls = [
+        call(
+            None, '/plinth/a', {
+                '/': {
+                    'tools.staticdir.root': '/b',
+                    'tools.staticdir.on': True,
+                    'tools.staticdir.dir': '.'
+                }
+            }),
+        call(
+            None, '/plinth/c', {
+                '/': {
+                    'tools.staticdir.root': '/d',
+                    'tools.staticdir.on': True,
+                    'tools.staticdir.dir': '.'
+                }
+            })
+    ]
+    mount.assert_has_calls(calls)

plinth/web_server.py

@@ -8,7 +8,7 @@ import os
 
 import cherrypy
 
-from . import cfg, log, module_loader, web_framework
+from . import app, cfg, log, module_loader, web_framework
 
 logger = logging.getLogger(__name__)
 
@@ -72,6 +72,9 @@ def init():
         urlprefix = "%s%s" % (web_framework.get_static_url(), module_name)
         _mount_static_directory(static_dir, urlprefix)
 
+    for component in StaticFiles.list():
+        component.mount()
+
     cherrypy.engine.signal_handler.subscribe()
 
 
@@ -80,3 +83,54 @@ def run(on_web_server_stop):
     cherrypy.engine.start()
     cherrypy.engine.subscribe('stop', on_web_server_stop)
     cherrypy.engine.block()
+
+
+class StaticFiles(app.FollowerComponent):
+    """Component to serve static files shipped with an app.
+
+    Any files in <app>/static directory will be automatically served on
+    /static/<app>/ directory by FreedomBox. This allows each app to ship custom
+    static files that are served by the web server.
+
+    However, in some rare circumstances, a system folder will need to be served
+    on a path for the app to work. This component allows declaring such
+    directories and the web paths they should be served on.
+
+    """
+
+    _all_instances = {}
+
+    def __init__(self, component_id, directory_map=None):
+        """Initialize the component.
+
+        component_id should be a unique ID across all components of an app and
+        across all components.
+
+        directory_map should be a dictionary with keys to be web paths and
+        values to be absolute path of the directory on disk to serve. The
+        static files from the directory are served over the given web path. The
+        web path will be prepended with the FreedomBox's configured base web
+        path. For example, {'/foo': '/usr/share/foo'} means that
+        '/usr/share/foo/bar.png' will be served over '/plinth/foo/bar.png' if
+        FreedomBox is configured to be served on '/plinth'.
+
+        """
+        super().__init__(component_id)
+        self.directory_map = directory_map
+        self._all_instances[component_id] = self
+
+    @classmethod
+    def list(cls):
+        """Return a list of all instances."""
+        return cls._all_instances.values()
+
+    def mount(self):
+        """Perform configuration of the web server to handle static files.
+
+        Called by web server abstraction layer after web server has been setup.
+
+        """
+        if self.directory_map:
+            for web_path, file_path in self.directory_map.items():
+                web_path = '%s%s' % (cfg.server_dir, web_path)
+                _mount_static_directory(file_path, web_path)