New handle_exception plugin hook, refs #1770

Also refs:
- https://github.com/simonw/datasette-sentry/issues/1
- https://github.com/simonw/datasette-show-errors/issues/2

datasette/handle_exception.py

@@ -0,0 +1,74 @@
+from datasette import hookimpl, Response
+from .utils import await_me_maybe, add_cors_headers
+from .utils.asgi import (
+    Base400,
+    Forbidden,
+)
+from .views.base import DatasetteError
+from markupsafe import Markup
+import pdb
+import traceback
+from .plugins import pm
+
+try:
+    import rich
+except ImportError:
+    rich = None
+
+
+@hookimpl(trylast=True)
+def handle_exception(datasette, request, exception):
+    async def inner():
+        if datasette.pdb:
+            pdb.post_mortem(exception.__traceback__)
+
+        if rich is not None:
+            rich.get_console().print_exception(show_locals=True)
+
+        title = None
+        if isinstance(exception, Base400):
+            status = exception.status
+            info = {}
+            message = exception.args[0]
+        elif isinstance(exception, DatasetteError):
+            status = exception.status
+            info = exception.error_dict
+            message = exception.message
+            if exception.message_is_html:
+                message = Markup(message)
+            title = exception.title
+        else:
+            status = 500
+            info = {}
+            message = str(exception)
+            traceback.print_exc()
+        templates = [f"{status}.html", "error.html"]
+        info.update(
+            {
+                "ok": False,
+                "error": message,
+                "status": status,
+                "title": title,
+            }
+        )
+        headers = {}
+        if datasette.cors:
+            add_cors_headers(headers)
+        if request.path.split("?")[0].endswith(".json"):
+            return Response.json(info, status=status, headers=headers)
+        else:
+            template = datasette.jinja_env.select_template(templates)
+            return Response.html(
+                await template.render_async(
+                    dict(
+                        info,
+                        urls=datasette.urls,
+                        app_css_hash=datasette.app_css_hash(),
+                        menu_links=lambda: [],
+                    )
+                ),
+                status=status,
+                headers=headers,
+            )
+
+    return inner