Add Flask host_matching support to admin instances

doc/advanced.rst

@@ -68,6 +68,55 @@ header to make the selection automatically.
 If the built-in translations are not enough, look at the `Flask-Babel documentation <https://pythonhosted.org/Flask-Babel/>`_
 to see how you can add your own.
 
+Using with Flask in `host_matching` mode
+----------------------------------------
+
+****
+
+If Flask is configured with `host_matching` enabled, then all routes registered on the app need to know which host(s) they should be served for.
+
+This requires some additional explicit configuration for Flask-Admin by passing the `host` argument to `Admin()` calls.
+
+#. With your Flask app initialised::
+
+        from flask import Flask
+        app = Flask(__name__, host='my.domain.com', static_host='static.domain.com')
+
+
+Serving Flask-Admin on a single, explicit host
+**********************************************
+Construct your Admin instance(s) and pass the desired `host` for the admin instance::
+
+        class AdminView(admin.BaseView):
+            @admin.expose('/')
+            def index(self):
+                return self.render('template.html')
+
+        admin1 = admin.Admin(app, url='/admin', host='admin.domain.com')
+        admin1.add_view(AdminView())
+
+Flask's `url_for` calls will work without any additional configuration/information::
+
+        url_for('admin.index', _external=True) == 'http://admin.domain.com/admin')
+
+
+Serving Flask-Admin on all hosts
+********************************
+Pass a wildcard to the `host` parameter to serve the admin instance on all hosts::
+
+        class AdminView(admin.BaseView):
+            @admin.expose('/')
+            def index(self):
+                return self.render('template.html')
+
+        admin1 = admin.Admin(app, url='/admin', host='*')
+        admin1.add_view(AdminView())
+
+If you need to generate URLs for a wildcard admin instance, you will need to pass `admin_routes_host` to the `url_for` call::
+
+        url_for('admin.index', admin_routes_host='admin.domain.com', _external=True) == 'http://admin.domain.com/admin')
+        url_for('admin.index', admin_routes_host='admin2.domain.com', _external=True) == 'http://admin2.domain.com/admin')
+
 .. _file-admin:
 
 Managing Files & Folders

examples/host-matching/README.rst

@@ -0,0 +1,21 @@
+This example shows how to configure Flask-Admin when you're using Flask's `host_matching` mode. Any Flask-Admin instance can be exposed on just a specific host, or on every host.
+
+To run this example:
+
+1. Clone the repository::
+
+    git clone https://github.com/flask-admin/flask-admin.git
+    cd flask-admin
+
+2. Create and activate a virtual environment::
+
+    python3 -m venv .venv
+    source .venv/bin/activate
+
+3. Install requirements::
+
+    pip install -r 'examples/host-matching/requirements.txt'
+
+4. Run the application::
+
+    python examples/host-matching/app.py

examples/host-matching/app.py

@@ -0,0 +1,55 @@
+from flask import Flask, url_for
+
+import flask_admin as admin
+
+
+# Views
+class FirstView(admin.BaseView):
+    @admin.expose('/')
+    def index(self):
+        return self.render('first.html')
+
+
+class SecondView(admin.BaseView):
+    @admin.expose('/')
+    def index(self):
+        return self.render('second.html')
+
+
+class ThirdViewAllHosts(admin.BaseView):
+    @admin.expose('/')
+    def index(self):
+        return self.render('third.html')
+
+
+# Create flask app
+app = Flask(__name__, template_folder='templates', host_matching=True, static_host='static.localhost:5000')
+
+
+# Flask views
+@app.route('/', host='<anyhost>')
+def index(anyhost):
+    return (
+        f'<a href="{url_for("admin.index")}">Click me to get to Admin 1</a>'
+        f'<br/>'
+        f'<a href="{url_for("admin2.index")}">Click me to get to Admin 2</a>'
+        f'<br/>'
+        f'<a href="{url_for("admin3.index", admin_routes_host="anything.localhost:5000")}">Click me to get to Admin 3 under `anything.localhost:5000`</a>'
+    )
+
+
+if __name__ == '__main__':
+    # Create first administrative interface at `first.localhost:5000/admin1`
+    admin1 = admin.Admin(app, url='/admin1', host='first.localhost:5000')
+    admin1.add_view(FirstView())
+
+    # Create second administrative interface at `second.localhost:5000/admin2`
+    admin2 = admin.Admin(app, url='/admin2', endpoint='admin2', host='second.localhost:5000')
+    admin2.add_view(SecondView())
+
+    # Create third administrative interface, available on any domain at `/admin3`
+    admin3 = admin.Admin(app, url='/admin3', endpoint='admin3', host='*')
+    admin3.add_view(ThirdViewAllHosts())
+
+    # Start app
+    app.run(debug=True)

examples/host-matching/requirements.txt

@@ -0,0 +1,2 @@
+Flask
+Flask-Admin

examples/host-matching/templates/first.html

@@ -0,0 +1,4 @@
+{% extends 'admin/master.html' %}
+{% block body %}
+    First admin view.
+{% endblock %}

examples/host-matching/templates/second.html

@@ -0,0 +1,4 @@
+{% extends 'admin/master.html' %}
+{% block body %}
+    Second admin view.
+{% endblock %}

examples/host-matching/templates/third.html

@@ -0,0 +1,4 @@
+{% extends 'admin/master.html' %}
+{% block body %}
+    Third admin view.
+{% endblock %}

flask_admin/base.py

@@ -1,14 +1,17 @@
 import os.path as op
+import typing as t
 import warnings
 
 from functools import wraps
 
-from flask import Blueprint, current_app, render_template, abort, g, url_for
+from flask import current_app, render_template, abort, g, url_for, request
 from flask_admin import babel
 from flask_admin._compat import as_unicode
 from flask_admin import helpers as h
 
 # For compatibility reasons import MenuLink
+from flask_admin.blueprints import _BlueprintWithHostSupport as Blueprint
+from flask_admin.consts import ADMIN_ROUTES_HOST_VARIABLE
 from flask_admin.menu import MenuCategory, MenuView, MenuLink, SubMenuCategory  # noqa: F401
 
 
@@ -268,6 +271,10 @@ def create_blueprint(self, admin):
                                    template_folder=op.join('templates', self.admin.template_mode),
                                    static_folder=self.static_folder,
                                    static_url_path=self.static_url_path)
+        self.blueprint.attach_url_defaults_and_value_preprocessor(
+            app=self.admin.app,
+            host=self.admin.host
+        )
 
         for url, name, methods in self._urls:
             self.blueprint.add_url_rule(url,
@@ -467,7 +474,8 @@ def __init__(self, app=None, name=None,
                  static_url_path=None,
                  base_template=None,
                  template_mode=None,
-                 category_icon_classes=None):
+                 category_icon_classes=None,
+                 host=None):
         """
             Constructor.
 
@@ -498,6 +506,8 @@ def __init__(self, app=None, name=None,
             :param category_icon_classes:
                 A dict of category names as keys and html classes as values to be added to menu category icons.
                 Example: {'Favorites': 'glyphicon glyphicon-star'}
+            :param host:
+                The host to register all admin views on. Mutually exclusive with `subdomain`
         """
         self.app = app
 
@@ -517,17 +527,42 @@ def __init__(self, app=None, name=None,
         self.url = url or self.index_view.url
         self.static_url_path = static_url_path
         self.subdomain = subdomain
+        self.host = host
         self.base_template = base_template or 'admin/base.html'
         self.template_mode = template_mode or 'bootstrap2'
         self.category_icon_classes = category_icon_classes or dict()
 
+        self._validate_admin_host_and_subdomain()
+
         # Add index view
         self._set_admin_index_view(index_view=index_view, endpoint=endpoint, url=url)
 
         # Register with application
         if app is not None:
             self._init_extension()
 
+    def _validate_admin_host_and_subdomain(self):
+        if self.subdomain is not None and self.host is not None:
+            raise ValueError("`subdomain` and `host` are mutually-exclusive")
+
+        if self.host is None:
+            return
+
+        if self.app and not self.app.url_map.host_matching:
+            raise ValueError(
+                "`host` should only be set if your Flask app is using `host_matching`."
+            )
+
+        if self.host.strip() in {"*", ADMIN_ROUTES_HOST_VARIABLE}:
+            self.host = ADMIN_ROUTES_HOST_VARIABLE
+
+        elif "<" in self.host and ">" in self.host:
+            raise ValueError(
+                "`host` must either be a host name with no variables, to serve all "
+                "Flask-Admin routes from a single host, or `*` to match the current "
+                "request's host."
+            )
+
     def add_view(self, view):
         """
             Add a view to the collection.
@@ -540,7 +575,10 @@ def add_view(self, view):
 
         # If app was provided in constructor, register view with Flask app
         if self.app is not None:
-            self.app.register_blueprint(view.create_blueprint(self))
+            self.app.register_blueprint(
+                view.create_blueprint(self),
+                host=self.host,
+            )
 
         self._add_view_to_menu(view)
 
@@ -708,6 +746,7 @@ def init_app(self, app, index_view=None,
                 Flask application instance
         """
         self.app = app
+        self._validate_admin_host_and_subdomain()
 
         self._init_extension()
 
@@ -721,7 +760,10 @@ def init_app(self, app, index_view=None,
 
         # Register views
         for view in self._views:
-            app.register_blueprint(view.create_blueprint(self))
+            app.register_blueprint(
+                view.create_blueprint(self),
+                host=self.host
+            )
 
     def _init_extension(self):
         if not hasattr(self.app, 'extensions'):

flask_admin/blueprints.py

@@ -0,0 +1,59 @@
+import typing as t
+
+from flask import request, Flask
+from flask.blueprints import Blueprint as FlaskBlueprint
+from flask.blueprints import BlueprintSetupState as FlaskBlueprintSetupState
+
+from flask_admin.consts import ADMIN_ROUTES_HOST_VARIABLE_NAME, \
+    ADMIN_ROUTES_HOST_VARIABLE
+
+
+class _BlueprintSetupStateWithHostSupport(FlaskBlueprintSetupState):
+    """Adds the ability to set a hostname on all routes when registering the blueprint."""
+
+    def __init__(self, blueprint, app, options, first_registration):
+        super().__init__(blueprint, app, options, first_registration)
+        self.host = self.options.get("host")
+
+    def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
+        # Ensure that every route registered by this blueprint has the host parameter
+        options.setdefault("host", self.host)
+        super().add_url_rule(rule, endpoint, view_func, **options)
+
+
+class _BlueprintWithHostSupport(FlaskBlueprint):
+    def make_setup_state(self, app, options, first_registration=False):
+        return _BlueprintSetupStateWithHostSupport(
+            self, app, options, first_registration
+        )
+
+    def attach_url_defaults_and_value_preprocessor(self, app: Flask, host: str):
+        if host != ADMIN_ROUTES_HOST_VARIABLE:
+            return
+
+        # Automatically inject `admin_routes_host` into `url_for` calls on admin
+        # endpoints.
+        @self.url_defaults
+        def inject_admin_routes_host_if_required(
+            endpoint: str, values: t.Dict[str, t.Any]
+        ) -> None:
+            if app.url_map.is_endpoint_expecting(
+                endpoint, ADMIN_ROUTES_HOST_VARIABLE_NAME
+            ):
+                values.setdefault(ADMIN_ROUTES_HOST_VARIABLE_NAME, request.host)
+
+        # Automatically strip `admin_routes_host` from the endpoint values so
+        # that the view methods don't receive that parameter, as it's not actually
+        # required by any of them.
+        @self.url_value_preprocessor
+        def strip_admin_routes_host_from_static_endpoint(
+            endpoint: t.Optional[str], values: t.Optional[t.Dict[str, t.Any]]
+        ) -> None:
+            if (
+                endpoint
+                and values
+                and app.url_map.is_endpoint_expecting(
+                    endpoint, ADMIN_ROUTES_HOST_VARIABLE_NAME
+                )
+            ):
+                values.pop(ADMIN_ROUTES_HOST_VARIABLE_NAME, None)

flask_admin/consts.py

@@ -6,3 +6,7 @@
 ICON_TYPE_IMAGE = 'image'
 # external image
 ICON_TYPE_IMAGE_URL = 'image-url'
+
+
+ADMIN_ROUTES_HOST_VARIABLE = "<admin_routes_host>"
+ADMIN_ROUTES_HOST_VARIABLE_NAME = "admin_routes_host"

flask_admin/tests/test_base.py

@@ -10,7 +10,7 @@
 
 @pytest.fixture
 def app():
-    # Overrides the `app` fixture in `flask_admin/tests/conftest.py` so that the `sqla`
+    # Overrides the `app` fixture in `flask_admin/tests/conftest.py` so that the `tests`
     # directory/import path is configured as the root path for Flask. This will
     # cause the `templates` directory here to be used for template resolution.
     app = Flask(__name__)