Add basic fallback error handler

locales/en_US/LC_MESSAGES/priviblur.po

@@ -133,6 +133,24 @@ msgstr "Priviblur was unable to complete the request to Tumblr before timing out
 msgid "priviblur_error_invalid_internal_tumblr_redirect"
 msgstr "Error: Tumblr HTTP 301 redirect points to foreign URL"
 
+msgid "priviblur_error_generic"
+msgstr "An unknown exception has occured!"
+
+msgid "priviblur_error_generic_description"
+msgstr "It looks like you have found a bug in Priviblur."
+
+msgid "priviblur_error_generic_description_2"
+msgstr "Please report it here at GitHub"
+
+msgid "priviblur_error_generic_technical_details_error_name"
+msgstr "Error: {0}"
+
+msgid "priviblur_error_generic_technical_details_error_message"
+msgstr "Message: {0}"
+
+msgid "priviblur_error_generic_technical_details_error_context"
+msgstr "Context:"
+
 msgid "post_community_label_mature_heading"
 msgstr "Community Label: Mature"
 

src/exceptions/error_handlers/_base.py

@@ -1,3 +1,5 @@
+import inspect
+
 class ErrorHandlerGroup:
     """Manages and registers error handler functions for specific exceptions
 
@@ -24,3 +26,35 @@ def register_handlers_into_app(self, app):
         for handler, exceptions in self.registered_handlers.items():
             for exception in exceptions:
                 app.error_handler.add(exception, handler)
+
+
+def create_user_friendly_error_message(request, exception):
+    # Taken from https://github.com/searxng/searxng/blob/f5eb56b63f250c7804e5e1cf4426e550bc933906/searx/metrics/error_recorder.py
+    exception_class = exception.__class__
+    exception_name = exception_class.__qualname__
+    exception_module = exception_class.__module__
+
+    if exception_module is None or exception_module == str.__class__.__module__:
+        processed_exception_name = exception_name
+    else:
+        processed_exception_name = f"{exception_module}.{exception_name}"
+
+    exception_message = str(exception) or None
+
+    frame = inspect.trace()
+    context = []
+
+    for trace in reversed(frame):
+        if trace.filename.startswith(request.app.ctx.PRIVIBLUR_PARENT_DIR_PATH):
+            local_path = trace.filename[len(request.app.ctx.PRIVIBLUR_PARENT_DIR_PATH) + 1:]
+        else:
+            local_path = trace.filename
+        occurrence = f"File \"{local_path}\" line {trace.lineno}: in {trace.function}"
+
+        # Add code context is applicable
+        if trace.code_context:
+            occurrence = f"{occurrence}\n  {trace.code_context[0].strip()}"
+
+        context.append(occurrence)
+
+    return processed_exception_name, exception_message, '\n'.join(context)

src/exceptions/error_handlers/miscellaneous_errors.py

@@ -49,3 +49,20 @@ async def invalid_redirect(request, exception):
         },
     status=502
     )
+
+
+@miscellaneous_errors.register(Exception)
+async def generic_error(request, exception):
+    name, message, context = _base.create_user_friendly_error_message(request, exception)
+
+    return await sanic_ext.render(
+        "misc/generic_error.jinja",
+        context={
+            "app": request.app,
+            "exception": exception,
+            "exception_name": name,
+            "exception_message": message,
+            "exception_context": context,
+        },
+    status=500
+    )

src/server.py

@@ -1,9 +1,7 @@
 import os
-import asyncio
 import logging
 import urllib.parse
 import functools
-import copy
 
 import sanic
 import aiohttp
@@ -61,6 +59,9 @@
 app.ctx.PRIVIBLUR_CONFIG = config
 app.ctx.translate = i18n.translate
 
+app.ctx.PRIVIBLUR_PARENT_DIR_PATH = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+
+
 @app.listener("before_server_start")
 async def initialize(app):
     priviblur_backend = app.ctx.PRIVIBLUR_CONFIG.backend

src/templates/misc/generic_error.jinja

@@ -0,0 +1,80 @@
+{# Displays information about some generic exception to the user #}
+
+{% extends "base.jinja" %}
+{% block head %}
+<style>
+#priviblur-error > div {
+    background-color: var(--color-top-level-card-bg);
+    border-radius: 25px;
+    padding: 25px;
+    max-width: 100%;
+}
+
+#priviblur-error h2 {
+    margin: 0;
+}
+
+#priviblur-error {
+    color: var(--color-text);
+}
+
+#priviblur-error details {
+    margin-top: 20px;
+}
+
+#priviblur-error pre {
+    text-wrap: wrap;
+}
+
+#priviblur-error a {
+    text-decoration: underline;
+}
+
+#error-header {
+    font-size: 16px;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 10px;
+}
+
+@media screen and (min-width: 768px) {
+    #priviblur-error pre {
+        text-wrap: nowrap;
+    }
+
+    #priviblur-error > div {
+        max-width: unset;
+        width: fit-content;
+    }
+}
+
+}
+</style>
+
+{% endblock %}
+{% block title %}Error{% endblock %}
+
+{% block center %}
+<section id="priviblur-error">
+    <div class="card">
+        <div id="error-header">
+            <h2>{{translate(request.ctx.language, "priviblur_error_generic")}}</h2>
+            <p>{{translate(request.ctx.language, "priviblur_error_generic_description")}}</p>
+            <a href="https://github.com/syeopite/priviblur/issues/new">{{translate(request.ctx.language, "priviblur_error_generic_description_2")}}</a>
+        </div>
+
+        <div>
+            <details open="">
+            <summary>Technical details</summary>
+                <pre>{{translate(request.ctx.language, "priviblur_error_generic_technical_details_error_name", substitution=exception_name)}}</pre>
+                {% if exception_message %}<pre>{{translate(request.ctx.language, "priviblur_error_generic_technical_details_error_message", substitution='"' + exception_message + '"')}}</pre>{% endif %}
+                <pre>{{-translate(request.ctx.language, "priviblur_error_generic_technical_details_error_context")}}</pre>
+                <pre>{{exception_context}}</pre>
+            </details>
+        </div>
+
+    </div>
+</section>
+{%- endblock %}