Show page when tag not found

wikinote/__init__.py

@@ -202,6 +202,9 @@ def tags_list():
 
 @app.route('/tag/<name>')
 def tag_view(name):
+	if name not in index['tags']:
+		return flask.render_template('tag_404.html', name=name)
+	
 	pages = index['tags'][name]
 	pages.sort(key=lambda p: p['kind'])
 	pages.sort(key=lambda p: p['path'])

wikinote/jinja2/tag_404.html

@@ -0,0 +1,36 @@
+{#
+    WikiNote3
+    Copyright © 2020  Lee Yingtong Li (RunasSudo)
+ 
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+ 
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+ 
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#}
+
+{% extends 'base.html' %}
+
+{% block title %}Tag: {{ name }} • WikiNote{% endblock %}
+
+{% block content %}
+	<nav class="breadcrumbs">
+		<a href="/"><img src="{{ url_for('static', filename='img/icons/home.svg') }}"></a>
+		&rsaquo;
+		<a href="{{ url_for('tags_list') }}">Tags</a>
+		&rsaquo;
+	</nav>
+	
+	<h1>{{ name }}</h1>
+	
+	<div class="admonition error">
+		There are no indexed pages with the name <em>{{ name }}</em>.
+	</div>
+{% endblock %}