`_
+for providing a response when an exception occurs. However, if you do no handle
+an exception, it will provide a fallback. There are three fallback types:
+
+- HTML - *default*
+- Text
+- JSON
+
+Setting ``app.config.FALLBACK_ERROR_FORMAT = "auto"`` will enable a switch that
+will attempt to provide an appropriate response format based upon the
+request type.
+"""
+
+import sys
+import typing as t
+from functools import partial
+from traceback import extract_tb
+
+from ..sanic.exceptions import InvalidUsage, SanicException
+from ..sanic.helpers import STATUS_CODES
+from ..sanic.request import Request
+from ..sanic.response import HTTPResponse, html, json, text
+
+try:
+ from ujson import dumps
+
+ dumps = partial(dumps, escape_forward_slashes=False)
+except ImportError: # noqa
+ from json import dumps # type: ignore
+
+
+FALLBACK_TEXT = (
+ "The server encountered an internal error and " "cannot complete your request."
+)
+FALLBACK_STATUS = 500
+
+
+class BaseRenderer:
+ """
+ Base class that all renderers must inherit from.
+ """
+
+ def __init__(self, request, exception, debug):
+ self.request = request
+ self.exception = exception
+ self.debug = debug
+
+ @property
+ def headers(self):
+ if isinstance(self.exception, SanicException):
+ return getattr(self.exception, "headers", {})
+ return {}
+
+ @property
+ def status(self):
+ if isinstance(self.exception, SanicException):
+ return getattr(self.exception, "status_code", FALLBACK_STATUS)
+ return FALLBACK_STATUS
+
+ @property
+ def text(self):
+ if self.debug or isinstance(self.exception, SanicException):
+ return str(self.exception)
+ return FALLBACK_TEXT
+
+ @property
+ def title(self):
+ status_text = STATUS_CODES.get(self.status, b"Error Occurred").decode()
+ return f"{self.status} — {status_text}"
+
+ def render(self) -> HTTPResponse:
+ """
+ Outputs the exception as a :class:`HTTPResponse`.
+
+ :return: The formatted exception
+ :rtype: str
+ """
+ output = (
+ self.full
+ if self.debug and not getattr(self.exception, "quiet", False)
+ else self.minimal
+ )
+ return output()
+
+ def minimal(self) -> HTTPResponse: # noqa
+ """
+ Provide a formatted message that is meant to not show any sensitive
+ data or details.
+ """
+ raise NotImplementedError
+
+ def full(self) -> HTTPResponse: # noqa
+ """
+ Provide a formatted message that has all details and is mean to be used
+ primarily for debugging and non-production environments.
+ """
+ raise NotImplementedError
+
+
+class HTMLRenderer(BaseRenderer):
+ """
+ Render an exception as HTML.
+
+ The default fallback type.
+ """
+
+ TRACEBACK_STYLE = """
+ html { font-family: sans-serif }
+ h2 { color: #888; }
+ .tb-wrapper p { margin: 0 }
+ .frame-border { margin: 1rem }
+ .frame-line > * { padding: 0.3rem 0.6rem }
+ .frame-line { margin-bottom: 0.3rem }
+ .frame-code { font-size: 16px; padding-left: 4ch }
+ .tb-wrapper { border: 1px solid #eee }
+ .tb-header { background: #eee; padding: 0.3rem; font-weight: bold }
+ .frame-descriptor { background: #e2eafb; font-size: 14px }
+ """
+ TRACEBACK_WRAPPER_HTML = (
+ ""
+ "{frame_html}
"
+ )
+ TRACEBACK_BORDER = (
+ ""
+ "The above exception was the direct cause of the following exception:"
+ "
"
+ )
+ TRACEBACK_LINE_HTML = (
+ ""
+ "
"
+ "File {0.filename}, line {0.lineno}, "
+ "in {0.name}"
+ "
{0.line}"
+ "
{title}
{text}\n"
+ "{body}"
+ )
+
+ def full(self) -> HTTPResponse:
+ return html(
+ self.OUTPUT_HTML.format(
+ title=self.title,
+ text=self.text,
+ style=self.TRACEBACK_STYLE,
+ body=self._generate_body(),
+ ),
+ status=self.status,
+ )
+
+ def minimal(self) -> HTTPResponse:
+ return html(
+ self.OUTPUT_HTML.format(
+ title=self.title,
+ text=self.text,
+ style=self.TRACEBACK_STYLE,
+ body="",
+ ),
+ status=self.status,
+ headers=self.headers,
+ )
+
+ @property
+ def text(self):
+ return escape(super().text)
+
+ @property
+ def title(self):
+ return escape(f"⚠️ {super().title}")
+
+ def _generate_body(self):
+ _, exc_value, __ = sys.exc_info()
+ exceptions = []
+ while exc_value:
+ exceptions.append(self._format_exc(exc_value))
+ exc_value = exc_value.__cause__
+
+ traceback_html = self.TRACEBACK_BORDER.join(reversed(exceptions))
+ appname = escape(self.request.app.name)
+ name = escape(self.exception.__class__.__name__)
+ value = escape(self.exception)
+ path = escape(self.request.path)
+ lines = [
+ f"
Traceback of {appname} (most recent call last):
",
+ f"{traceback_html}",
+ "",
+ f"{name}: {value} while handling path {path}",
+ "
+