169 lines (138 sloc) 6.33 KB
# -*- coding: utf-8 -*-
Various helpers to make the development experience better.
:copyright: © 2010 by the Pallets team.
:license: BSD, see LICENSE for more details.
import os
from warnings import warn
from ._compat import implements_to_string, text_type
from .app import Flask
from .blueprints import Blueprint
from .globals import _request_ctx_stack
class UnexpectedUnicodeError(AssertionError, UnicodeError):
"""Raised in places where we want some better error reporting for
unexpected unicode or binary data.
class DebugFilesKeyError(KeyError, AssertionError):
"""Raised from request.files during debugging. The idea is that it can
provide a better error message than just a generic KeyError/BadRequest.
def __init__(self, request, key):
form_matches = request.form.getlist(key)
buf = ['You tried to access the file "%s" in the request.files '
'dictionary but it does not exist. The mimetype for the request '
'is "%s" instead of "multipart/form-data" which means that no '
'file contents were transmitted. To fix this error you should '
'provide enctype="multipart/form-data" in your form.' %
(key, request.mimetype)]
if form_matches:
buf.append('\n\nThe browser instead transmitted some file names. '
'This was submitted: %s' % ', '.join('"%s"' % x
for x in form_matches))
self.msg = ''.join(buf)
def __str__(self):
return self.msg
class FormDataRoutingRedirect(AssertionError):
"""This exception is raised by Flask in debug mode if it detects a
redirect caused by the routing system when the request method is not
GET, HEAD or OPTIONS. Reasoning: form data will be dropped.
def __init__(self, request):
exc = request.routing_exception
buf = ['A request was sent to this URL (%s) but a redirect was '
'issued automatically by the routing system to "%s".'
% (request.url, exc.new_url)]
# In case just a slash was appended we can be extra helpful
if request.base_url + '/' == exc.new_url.split('?')[0]:
buf.append(' The URL was defined with a trailing slash so '
'Flask will automatically redirect to the URL '
'with the trailing slash if it was accessed '
'without one.')
buf.append(' Make sure to directly send your %s-request to this URL '
'since we can\'t make browsers or HTTP clients redirect '
'with form data reliably or without user interaction.' %
buf.append('\n\nNote: this exception is only raised in debug mode')
AssertionError.__init__(self, ''.join(buf).encode('utf-8'))
def attach_enctype_error_multidict(request):
"""Since Flask 0.8 we're monkeypatching the files object in case a
request is detected that does not use multipart form data but the files
object is accessed.
oldcls = request.files.__class__
class newcls(oldcls):
def __getitem__(self, key):
return oldcls.__getitem__(self, key)
except KeyError:
if key not in request.form:
raise DebugFilesKeyError(request, key)
newcls.__name__ = oldcls.__name__
newcls.__module__ = oldcls.__module__
request.files.__class__ = newcls
def _dump_loader_info(loader):
yield 'class: %s.%s' % (type(loader).__module__, type(loader).__name__)
for key, value in sorted(loader.__dict__.items()):
if key.startswith('_'):
if isinstance(value, (tuple, list)):
if not all(isinstance(x, (str, text_type)) for x in value):
yield '%s:' % key
for item in value:
yield ' - %s' % item
elif not isinstance(value, (str, text_type, int, float, bool)):
yield '%s: %r' % (key, value)
def explain_template_loading_attempts(app, template, attempts):
"""This should help developers understand what failed"""
info = ['Locating template "%s":' % template]
total_found = 0
blueprint = None
reqctx =
if reqctx is not None and reqctx.request.blueprint is not None:
blueprint = reqctx.request.blueprint
for idx, (loader, srcobj, triple) in enumerate(attempts):
if isinstance(srcobj, Flask):
src_info = 'application "%s"' % srcobj.import_name
elif isinstance(srcobj, Blueprint):
src_info = 'blueprint "%s" (%s)' % (,
src_info = repr(srcobj)
info.append('% 5d: trying loader of %s' % (
idx + 1, src_info))
for line in _dump_loader_info(loader):
info.append(' %s' % line)
if triple is None:
detail = 'no match'
detail = 'found (%r)' % (triple[1] or '<string>')
total_found += 1
info.append(' -> %s' % detail)
seems_fishy = False
if total_found == 0:
info.append('Error: the template could not be found.')
seems_fishy = True
elif total_found > 1:
info.append('Warning: multiple loaders returned a match for the template.')
seems_fishy = True
if blueprint is not None and seems_fishy:
info.append(' The template was looked up from an endpoint that '
'belongs to the blueprint "%s".' % blueprint)
info.append(' Maybe you did not place a template in the right folder?')
info.append(' See')'\n'.join(info))
def explain_ignored_app_run():
if os.environ.get('WERKZEUG_RUN_MAIN') != 'true':
warn(Warning('Silently ignoring because the '
'application is run from the flask command line '
'executable. Consider putting behind an '
'if __name__ == "__main__" guard to silence this '
'warning.'), stacklevel=3)