fix(FastAPI): add custom error templates for certain exceptions

Signed-off-by: Steven Guikal <void@fluix.one>

aurweb/asgi.py

@@ -1,6 +1,7 @@
 import asyncio
 import http
 import os
+import re
 import sys
 import typing
 
@@ -9,18 +10,22 @@ from urllib.parse import quote_plus
 from fastapi import FastAPI, HTTPException, Request, Response
 from fastapi.responses import RedirectResponse
 from fastapi.staticfiles import StaticFiles
+from jinja2 import TemplateNotFound
 from prometheus_client import multiprocess
 from sqlalchemy import and_, or_
+from starlette.exceptions import HTTPException as StarletteHTTPException
 from starlette.middleware.authentication import AuthenticationMiddleware
 from starlette.middleware.sessions import SessionMiddleware
 
 import aurweb.config
 import aurweb.logging
+import aurweb.pkgbase.util as pkgbaseutil
 
 from aurweb import prometheus, util
 from aurweb.auth import BasicAuthBackend
 from aurweb.db import get_engine, query
 from aurweb.models import AcceptedTerm, Term
+from aurweb.packages.util import get_pkg_or_base
 from aurweb.prometheus import instrumentator
 from aurweb.routers import APP_ROUTES
 from aurweb.templates import make_context, render_template
@@ -89,7 +94,7 @@ def child_exit(server, worker):  # pragma: no cover
     multiprocess.mark_process_dead(worker.pid)
 
 
-@app.exception_handler(HTTPException)
+@app.exception_handler(StarletteHTTPException)
 async def http_exception_handler(request: Request, exc: HTTPException) \
         -> Response:
     """ Handle an HTTPException thrown in a route. """
@@ -97,8 +102,24 @@ async def http_exception_handler(request: Request, exc: HTTPException) \
     context = make_context(request, phrase)
     context["exc"] = exc
     context["phrase"] = phrase
-    return render_template(request, "errors/detail.html", context,
-                           exc.status_code)
+
+    # Additional context for some exceptions.
+    if exc.status_code == http.HTTPStatus.NOT_FOUND:
+        tokens = request.url.path.split("/")
+        matches = re.match("^([a-z0-9][a-z0-9.+_-]*?)(\\.git)?$", tokens[1])
+        if matches:
+            try:
+                pkgbase = get_pkg_or_base(matches.group(1))
+                context = pkgbaseutil.make_context(request, pkgbase)
+            except HTTPException:
+                pass
+
+    try:
+        return render_template(request, f"errors/{exc.status_code}.html",
+                               context, exc.status_code)
+    except TemplateNotFound:
+        return render_template(request, "errors/detail.html",
+                               context, exc.status_code)
 
 
 @app.middleware("http")

aurweb/packages/util.py

@@ -87,11 +87,14 @@ def provides_markup(provides: Providers) -> str:
 
 def get_pkg_or_base(
         name: str,
-        cls: Union[models.Package, models.PackageBase] = models.PackageBase):
+        cls: Union[models.Package, models.PackageBase] = models.PackageBase) \
+        -> Union[models.Package, models.PackageBase]:
     """ Get a PackageBase instance by its name or raise a 404 if
     it can't be found in the database.
 
     :param name: {Package,PackageBase}.Name
+    :param exception: Whether to raise an HTTPException or simply return None if
+                      the package can't be found.
     :raises HTTPException: With status code 404 if record doesn't exist
     :return: {Package,PackageBase} instance
     """

templates/errors/404.html

@@ -0,0 +1,34 @@
+{% extends 'partials/layout.html' %}
+
+{% block pageContent %}
+    <div id="error-page" class="box">
+        <h2>404 - {% trans %}Page Not Found{% endtrans %}</h2>
+        <p>{% trans %}Sorry, the page you've requested does not exist.{% endtrans %}</p>
+        {% if pkgbase %}
+            <ul>
+                {% set pkgname_strong="<strong>%s</strong>" | format(pkgbase.Name) %}
+                <li>
+                    <strong>{% trans %}Note{% endtrans %}:</strong>
+                    {% trans %}Git clone URLs are not meant to be opened in a browser.{% endtrans %}
+                </li>
+                <li>
+                    {% set gitcmd="<code>git clone %s</code>" | format(git_clone_uri_anon | format(pkgbase.Name)) %}
+                    {% if is_maintainer %}
+                      {% set gitcmd="<code>git clone %s</code>" | format(git_clone_uri_priv | format(pkgbase.Name)) %}
+                    {% endif %}
+                    {{
+                        "To clone the Git repository of %s, run %s."
+                        | tr | format(pkgname_strong, gitcmd) | safe
+                    }}
+                </li>
+                <li>
+                    {% set pkglink='<a href="/pkgbase/%s">' | format(pkgbase.Name) %}
+                    {{
+                        "Click %shere%s to return to the %s details page."
+                        | tr | format(pkglink, "</a>", pkgname_strong) | safe
+                    }}
+                </li>
+            </ul>
+        {% endif %}
+    </div>
+{% endblock %}

templates/errors/503.html

@@ -0,0 +1,8 @@
+{% extends 'partials/layout.html' %}
+
+{% block pageContent %}
+    <div id="error-page" class="box">
+        <h2>503 - {% trans %}Service Unavailable{% endtrans %}</h2>
+        <p>{% trans %}Don't panic! This site is down due to maintenance. We will be back soon.{% endtrans %}</p>
+    </div>
+{% endblock %}