Source code
from __future__ import annotations
import collections.abc as cabc
import inspect
import os
import sys
import typing as t
import weakref
from datetime import timedelta
from functools import update_wrapper
from inspect import iscoroutinefunction
from itertools import chain
from types import TracebackType
from urllib.parse import quote as _url_quote
from urllib.parse import urlsplit
import click
from werkzeug.datastructures import Headers
from werkzeug.datastructures import ImmutableDict
from werkzeug.exceptions import BadRequestKeyError
from werkzeug.exceptions import HTTPException
from werkzeug.exceptions import InternalServerError
from werkzeug.routing import BuildError
from werkzeug.routing import MapAdapter
from werkzeug.routing import RequestRedirect
from werkzeug.routing import RoutingException
from werkzeug.routing import Rule
from werkzeug.serving import is_running_from_reloader
from werkzeug.wrappers import Response as BaseResponse
from werkzeug.wsgi import get_host
from . import cli
from . import typing as ft
from .ctx import AppContext
from .globals import _cv_app
from .globals import app_ctx
from .globals import g
from .globals import request
from .globals import session
from .helpers import _CollectErrors
from .helpers import get_debug_flag
from .helpers import get_flashed_messages
from .helpers import get_load_dotenv
from .helpers import send_from_directory
from .sansio.app import App
from .sessions import SecureCookieSessionInterface
from .sessions import SessionInterface
from .signals import appcontext_tearing_down
from .signals import got_request_exception
from .signals import request_finished
from .signals import request_started
from .signals import request_tearing_down
from .templating import Environment
from .wrappers import Request
from .wrappers import Response
class Flask(App):
"""The flask object implements a WSGI application and acts as the central
object. It is passed the name of the module or package of the
application. Once it is created it will act as a central registry for
the view functions, the URL rules, template configuration and much more.
The name of the package is used to resolve resources from inside the
package or the folder the module is contained in depending on if the
package parameter resolves to an actual python package (a folder with
an :file:`__init__.py` file inside) or a standard module (just a ``.py`` file).
For more information about resource loading, see :func:`open_resource`.
Usually you create a :class:`Flask` instance in your main module or
in the :file:`__init__.py` file of your package like this::
from flask import Flask
app = Flask(__name__)
.. admonition:: About the First Parameter
The idea of the first parameter is to give Flask an idea of what
belongs to your application. This name is used to find resources
on the filesystem, can be used by extensions to improve debugging
information and a lot more.
So it's important what you provide there. If you are using a single
module, `__name__` is always the correct value. If you however are
using a package, it's usually recommended to hardcode the name of
your package there.
For example if your application is defined in :file:`yourapplication/app.py`
you should create it with one of the two versions below::
app = Flask('yourapplication')
app = Flask(__name__.split('.')[0])
Why is that? The application will work even with `__name__`, thanks
to how resources are looked up. However it will make debugging more
painful. Certain extensions can make assumptions based on the
import name of your application. For example the Flask-SQLAlchemy
extension will look for the code in your application that triggered
an SQL query in debug mode. If the import name is not properly set
up, that debugging information is lost. (For example it would only
pick up SQL queries in `yourapplication.app` and not
`yourapplication.views.frontend`)
.. versionadded:: 0.7
The `static_url_path`, `static_folder`, and `template_folder`
parameters were added.
.. versionadded:: 0.8
The `instance_path` and `instance_relative_config` parameters were
added.
.. versionadded:: 0.11
The `root_path` parameter was added.
.. versionadded:: 1.0
The ``host_matching`` and ``static_host`` parameters were added.
.. versionadded:: 1.0
The ``subdomain_matching`` parameter was added. Subdomain
matching needs to be enabled manually now. Setting
:data:`SERVER_NAME` does not implicitly enable it.
:param import_name: the name of the application package
:param static_url_path: can be used to specify a different path for the
static files on the web. Defaults to the name
of the `static_folder` folder.
:param static_folder: The folder with static files that is served at
``static_url_path``. Relative to the application ``root_path``
or an absolute path. Defaults to ``'static'``.
:param static_host: the host to use when adding the static route.
Defaults to None. Required when using ``host_matching=True``
with a ``static_folder`` configured.
:param host_matching: set ``url_map.host_matching`` attribute.
Defaults to False.
:param subdomain_matching: consider the subdomain relative to
:data:`SERVER_NAME` when matching routes. Defaults to False.
:param template_folder: the folder that contains the templates that should
be used by the application. Defaults to
``'templates'`` folder in the root path of the
application.
:param instance_path: An alternative instance path for the application.
By default the folder ``'instance'`` next to the
package or module is assumed to be the instance
path.
:param instance_relative_config: if set to ``True`` relative filenames
for loading the config are assumed to
be relative to the instance path instead
of the application root.
:param root_path: The path to the root of the application files.
This should only be set manually when it can't be detected
automatically, such as for namespace packages.
"""
default_config = ImmutableDict(
{
"DEBUG": None,
"TESTING": False,
"PROPAGATE_EXCEPTIONS": None,
"SECRET_KEY": None,
"SECRET_KEY_FALLBACKS": None,
"PERMANENT_SESSION_LIFETIME": timedelta(days=31),
"USE_X_SENDFILE": False,
"TRUSTED_HOSTS": None,
"SERVER_NAME": None,
"APPLICATION_ROOT": "/",
"SESSION_COOKIE_NAME": "session",
"SESSION_COOKIE_DOMAIN": None,
"SESSION_COOKIE_PATH": None,
"SESSION_COOKIE_HTTPONLY": True,
"SESSION_COOKIE_SECURE": False,
"SESSION_COOKIE_PARTITIONED": False,
"SESSION_COOKIE_SAMESITE": None,
"SESSION_REFRESH_EACH_REQUEST": True,
"MAX_CONTENT_LENGTH": None,
"MAX_FORM_MEMORY_SIZE": 500_000,
"MAX_FORM_PARTS": 1_000,
"SEND_FILE_MAX_AGE_DEFAULT": None,
"TRAP_BAD_REQUEST_ERRORS": None,
"TRAP_HTTP_EXCEPTIONS": False,
"EXPLAIN_TEMPLATE_LOADING": False,
"PREFERRED_URL_SCHEME": "http",
"TEMPLATES_AUTO_RELOAD": None,
"MAX_COOKIE_SIZE": 4093,
"PROVIDE_AUTOMATIC_OPTIONS": True,
}
)
#: The class that is used for request objects. See :class:`~flask.Request`
#: for more information.
request_class: type[Request] = Request
#: The class that is used for response objects. See
#: :class:`~flask.Response` for more information.
response_class: type[Response] = Response
#: the session interface to use. By default an instance of
#: :class:`~flask.sessions.SecureCookieSessionInterface` is used here.
#:
#: .. versionadded:: 0.8
session_interface: SessionInterface = SecureCookieSessionInterface()
def __init_subclass__(cls, **kwargs: t.Any) -> None:
import warnings
# These method signatures were updated to take a ctx param. Detect
# overridden methods in subclasses that still have the old signature.
# Show a deprecation warning and wrap to call with correct args.
for method in (
cls.handle_http_exception,
cls.handle_user_exception,
cls.handle_exception,
cls.log_exception,
cls.dispatch_request,
cls.full_dispatch_request,
cls.finalize_request,
cls.make_default_options_response,
cls.preprocess_request,
cls.process_response,
cls.do_teardown_request,
cls.do_teardown_appcontext,
):
base_method = getattr(Flask, method.__name__)
if method is base_method:
# not overridden
continue
# get the second parameter (first is self)
iter_params = iter(inspect.signature(method).parameters.values())
next(iter_params)
param = next(iter_params, None)
# must have second parameter named ctx or annotated AppContext
if param is None or not (
# no annotation, match name
(param.annotation is inspect.Parameter.empty and param.name == "ctx")
or (
# string annotation, access path ends with AppContext
isinstance(param.annotation, str)
and param.annotation.rpartition(".")[2] == "AppContext"
)
or (
# class annotation
inspect.isclass(param.annotation)
and issubclass(param.annotation, AppContext)
)
):
warnings.warn(
f"The '{method.__name__}' method now takes 'ctx: AppContext'"
" as the first parameter. The old signature is deprecated"
" and will not be supported in Flask 4.0.",
DeprecationWarning,
stacklevel=2,
)
setattr(cls, method.__name__, remove_ctx(method))
setattr(Flask, method.__name__, add_ctx(base_method))
def __init__(
self,
import_name: str,
static_url_path: str | None = None,
static_folder: str | os.PathLike[str] | None = "static",
static_host: str | None = None,
host_matching: bool = False,
subdomain_matching: bool = False,
template_folder: str | os.PathLike[str] | None = "templates",
instance_path: str | None = None,
instance_relative_config: bool = False,
root_path: str | None = None,
):
super().__init__(
import_name=import_name,
static_url_path=static_url_path,
static_folder=static_folder,
static_host=static_host,
host_matching=host_matching,
subdomain_matching=subdomain_matching,
template_folder=template_folder,
instance_path=instance_path,
instance_relative_config=instance_relative_config,
root_path=root_path,
)
#: The Click command group for registering CLI commands for this
#: object. The commands are available from the ``flask`` command
#: once the application has been discovered and blueprints have
#: been registered.
self.cli = cli.AppGroup()
# Set the name of the Click group in case someone wants to add
# the app's commands to another CLI tool.
self.cli.name = self.name
# Add a static route using the provided static_url_path, static_host,
# and static_folder if there is a configured static_folder.
# Note we do this without checking if static_folder exists.
# For one, it might be created while the server is running (e.g. during
# development). Also, Google App Engine stores static files somewhere
if self.has_static_folder:
assert bool(static_host) == host_matching, (
"Invalid static_host/host_matching combination"
)
# Use a weakref to avoid creating a reference cycle between the app
# and the view function (see #3761).
self_ref = weakref.ref(self)
self.add_url_rule(
f"{self.static_url_path}/<path:filename>",
endpoint="static",
host=static_host,
view_func=lambda **kw: self_ref().send_static_file(**kw), # type: ignore
)
def get_send_file_max_age(self, filename: str | None) -> int | None:
"""Used by :func:`send_file` to determine the ``max_age`` cache
value for a given file path if it wasn't passed.
By default, this returns :data:`SEND_FILE_MAX_AGE_DEFAULT` from
the configuration of :data:`~flask.current_app`. This defaults
to ``None``, which tells the browser to use conditional requests
instead of a timed cache, which is usually preferable.
Note this is a duplicate of the same method in the Flask
class.
.. versionchanged:: 2.0
The default configuration is ``None`` instead of 12 hours.
.. versionadded:: 0.9
"""
value = self.config["SEND_FILE_MAX_AGE_DEFAULT"]
if value is None:
return None
if isinstance(value, timedelta):
return int(value.total_seconds())
return value # type: ignore[no-any-return]
def send_static_file(self, filename: str) -> Response:
"""The view function used to serve files from
:attr:`static_folder`. A route is automatically registered for
this view at :attr:`static_url_path` if :attr:`static_folder` is
set.
Note this is a duplicate of the same method in the Flask
class.
.. versionadded:: 0.5
"""
if not self.has_static_folder:
raise RuntimeError("'static_folder' must be set to serve static_files.")
# send_file only knows to call get_send_file_max_age on the app,
# call it here so it works for blueprints too.
max_age = self.get_send_file_max_age(filename)
return send_from_directory(
t.cast(str, self.static_folder), filename, max_age=max_age
)
def open_resource(
self, resource: str, mode: str = "rb", encoding: str | None = None
) -> t.IO[t.AnyStr]:
"""Open a resource file relative to :attr:`root_path` for reading.
For example, if the file ``schema.sql`` is next to the file
``app.py`` where the ``Flask`` app is defined, it can be opened
with:
.. code-block:: python
with app.open_resource("schema.sql") as f:
conn.executescript(f.read())
:param resource: Path to the resource relative to :attr:`root_path`.
:param mode: Open the file in this mode. Only reading is supported,
valid values are ``"r"`` (or ``"rt"``) and ``"rb"``.
:param encoding: Open the file with this encoding when opening in text
mode. This is ignored when opening in binary mode.
.. versionchanged:: 3.1
Added the ``encoding`` parameter.
"""
if mode not in {"r", "rt", "rb"}:
raise ValueError("Resources can only be opened for reading.")
path = os.path.join(self.root_path, resource)
if mode == "rb":
return open(path, mode) # pyright: ignore
return open(path, mode, encoding=encoding)
def open_instance_resource(
self, resource: str, mode: str = "rb", encoding: str | None = "utf-8"
) -> t.IO[t.AnyStr]:
"""Open a resource file relative to the application's instance folder
:attr:`instance_path`. Unlike :meth:`open_resource`, files in the
instance folder can be opened for writing.
:param resource: Path to the resource relative to :attr:`instance_path`.
:param mode: Open the file in this mode.
:param encoding: Open the file with this encoding when opening in text
mode. This is ignored when opening in binary mode.
.. versionchanged:: 3.1
Added the ``encoding`` parameter.
"""
path = os.path.join(self.instance_path, resource)
if "b" in mode:
return open(path, mode)
return open(path, mode, encoding=encoding)
def create_jinja_environment(self) -> Environment:
"""Create the Jinja environment based on :attr:`jinja_options`
and the various Jinja-related methods of the app. Changing
:attr:`jinja_options` after this will have no effect. Also adds
Flask-related globals and filters to the environment.
.. versionchanged:: 0.11
``Environment.auto_reload`` set in accordance with
``TEMPLATES_AUTO_RELOAD`` configuration option.
.. versionadded:: 0.5
"""
options = dict(self.jinja_options)
if "autoescape" not in options:
options["autoescape"] = self.select_jinja_autoescape
if "auto_reload" not in options:
auto_reload = self.config["TEMPLATES_AUTO_RELOAD"]
if auto_reload is None:
auto_reload = self.debug
options["auto_reload"] = auto_reload
rv = self.jinja_environment(self, **options)
rv.globals.update(
url_for=self.url_for,
get_flashed_messages=get_flashed_messages,
config=self.config,
# request, session and g are normally added with the
# context processor for efficiency reasons but for imported
# templates we also want the proxies in there.
request=request,
session=session,
g=g,
)
rv.policies["json.dumps_function"] = self.json.dumps
return rv
def create_url_adapter(self, request: Request | None) -> MapAdapter | None:
"""Creates a URL adapter for the given request. The URL adapter
is created at a point where the request context is not yet set
up so the request is passed explicitly.
.. versionchanged:: 3.1
If :data:`SERVER_NAME` is set, it does not restrict requests to
only that domain, for both ``subdomain_matching`` and
``host_matching``.
.. versionchanged:: 1.0
:data:`SERVER_NAME` no longer implicitly enables subdomain
matching. Use :attr:`subdomain_matching` instead.
.. versionchanged:: 0.9
This can be called outside a request when the URL adapter is created
for an application context.
.. versionadded:: 0.6
"""
if request is not None:
if (trusted_hosts := self.config["TRUSTED_HOSTS"]) is not None:
request.trusted_hosts = trusted_hosts
# Check trusted_hosts here until bind_to_environ does.
request.host = get_host(request.environ, request.trusted_hosts) # pyright: ignore
subdomain = None
server_name = self.config["SERVER_NAME"]
if self.url_map.host_matching:
# Don't pass SERVER_NAME, otherwise it's used and the actual
# host is ignored, which breaks host matching.
server_name = None
elif not self.subdomain_matching:
# Werkzeug doesn't implement subdomain matching yet. Until then,
# disable it by forcing the current subdomain to the default, or
# the empty string.
subdomain = self.url_map.default_subdomain or ""
return self.url_map.bind_to_environ(
request.environ, server_name=server_name, subdomain=subdomain
)
# Need at least SERVER_NAME to match/build outside a request.
if self.config["SERVER_NAME"] is not None:
return self.url_map.bind(
self.config["SERVER_NAME"],
script_name=self.config["APPLICATION_ROOT"],
url_scheme=self.config["PREFERRED_URL_SCHEME"],
)
return None
def raise_routing_exception(self, request: Request) -> t.NoReturn:
"""Intercept routing exceptions and possibly do something else.
In debug mode, intercept a routing redirect and replace it with
an error if the body will be discarded.
With modern Werkzeug this shouldn't occur, since it now uses a
308 status which tells the browser to resend the method and
body.
.. versionchanged:: 2.1
Don't intercept 307 and 308 redirects.
:meta private:
:internal:
"""
if (
not self.debug
or not isinstance(request.routing_exception, RequestRedirect)
or request.routing_exception.code in {307, 308}
or request.method in {"GET", "HEAD", "OPTIONS"}
):
raise request.routing_exception # type: ignore[misc]
from .debughelpers import FormDataRoutingRedirect
raise FormDataRoutingRedirect(request)
def update_template_context(
self, ctx: AppContext, context: dict[str, t.Any]
) -> None:
"""Update the template context with some commonly used variables.
This injects request, session, config and g into the template
context as well as everything template context processors want
to inject. Note that the as of Flask 0.6, the original values
in the context will not be overridden if a context processor
decides to return a value with the same key.
:param context: the context as a dictionary that is updated in place
to add extra variables.
"""
names: t.Iterable[str | None] = (None,)
# A template may be rendered outside a request context.
if ctx.has_request:
names = chain(names, reversed(ctx.request.blueprints))
# The values passed to render_template take precedence. Keep a
# copy to re-apply after all context functions.
orig_ctx = context.copy()
loopIteratorH = __import__("builtins").iter(names)
while True:
try:
name = __import__("builtins").next(loopIteratorH)
except __import__("builtins").StopIteration:
break
if name in self.template_context_processors:
loopIterator = __import__("builtins").iter(self.template_context_processors[name])
while True:
try:
func = __import__("builtins").next(loopIterator)
except __import__("builtins").StopIteration:
break
context.update(self.ensure_sync(func)())
context.update(orig_ctx)
def make_shell_context(self) -> dict[str, t.Any]:
"""Returns the shell context for an interactive shell for this
application. This runs all the registered shell context
processors.
.. versionadded:: 0.11
"""
rv = {"app": self, "g": g}
loopIteratorA = __import__("builtins").iter(self.shell_context_processors)
while True:
try:
processor = __import__("builtins").next(loopIteratorA)
except __import__("builtins").StopIteration:
break
rv.update(processor())
return rv
def run(
self,
host: str | None = None,
port: int | None = None,
debug: bool | None = None,
load_dotenv: bool = True,
**options: t.Any,
) -> None:
"""Runs the application on a local development server.
Do not use ``run()`` in a production setting. It is not intended to
meet security and performance requirements for a production server.
Instead, see :doc:`/deploying/index` for WSGI server recommendations.
If the :attr:`debug` flag is set the server will automatically reload
for code changes and show a debugger in case an exception happened.
If you want to run the application in debug mode, but disable the
code execution on the interactive debugger, you can pass
``use_evalex=False`` as parameter. This will keep the debugger's
traceback screen active, but disable code execution.
It is not recommended to use this function for development with
automatic reloading as this is badly supported. Instead you should
be using the :command:`flask` command line script's ``run`` support.
.. admonition:: Keep in Mind
Flask will suppress any server error with a generic error page
unless it is in debug mode. As such to enable just the
interactive debugger without the code reloading, you have to
invoke :meth:`run` with ``debug=True`` and ``use_reloader=False``.
Setting ``use_debugger`` to ``True`` without being in debug mode
won't catch any exceptions because there won't be any to
catch.
:param host: the hostname to listen on. Set this to ``'0.0.0.0'`` to
have the server available externally as well. Defaults to
``'127.0.0.1'`` or the host in the ``SERVER_NAME`` config variable
if present.
:param port: the port of the webserver. Defaults to ``5000`` or the
port defined in the ``SERVER_NAME`` config variable if present.
:param debug: if given, enable or disable debug mode. See
:attr:`debug`.
:param load_dotenv: Load the nearest :file:`.env` and :file:`.flaskenv`
files to set environment variables. Will also change the working
directory to the directory containing the first file found.
:param options: the options to be forwarded to the underlying Werkzeug
server. See :func:`werkzeug.serving.run_simple` for more
information.
.. versionchanged:: 1.0
If installed, python-dotenv will be used to load environment
variables from :file:`.env` and :file:`.flaskenv` files.
The :envvar:`FLASK_DEBUG` environment variable will override :attr:`debug`.
Threaded mode is enabled by default.
.. versionchanged:: 0.10
The default port is now picked from the ``SERVER_NAME``
variable.
"""
# Ignore this call so that it doesn't start another server if
# the 'flask run' command is used.
if os.environ.get("FLASK_RUN_FROM_CLI") == "true":
if not is_running_from_reloader():
click.secho(
" * Ignoring a call to 'app.run()' that would block"
" the current 'flask' CLI command.\n"
" Only call 'app.run()' in an 'if __name__ =="
' "__main__"\' guard.',
fg="red",
)
return
if get_load_dotenv(load_dotenv):
cli.load_dotenv()
# if set, env var overrides existing value
if "FLASK_DEBUG" in os.environ:
self.debug = get_debug_flag()
# debug passed to method overrides all other sources
if debug is not None:
self.debug = bool(debug)
server_name = self.config.get("SERVER_NAME")
sn_host = sn_port = None
if server_name:
server_url = urlsplit(f"//{server_name}")
sn_host = server_url.hostname
sn_port = server_url.port
if not host:
if sn_host:
host = sn_host
else:
host = "127.0.0.1"
if port or port == 0:
port = int(port)
elif sn_port is not None:
port = sn_port
else:
port = 5000
options.setdefault("use_reloader", self.debug)
options.setdefault("use_debugger", self.debug)
options.setdefault("threaded", True)
cli.show_server_banner(self.debug, self.name)
from werkzeug.serving import run_simple
try:
run_simple(host, port, self, **options)
finally:
# reset the first request information if the development server
# reset normally. This makes it possible to restart the server
# without reloader and that stuff from an interactive shell.
self._got_first_request = False
def test_client(self, use_cookies: bool = True, **kwargs: t.Any) -> FlaskClient:
"""Creates a test client for this application. For information
about unit testing head over to :doc:`/testing`.
Note that if you are testing for assertions or exceptions in your
application code, you must set ``app.testing = True`` in order for the
exceptions to propagate to the test client. Otherwise, the exception
will be handled by the application (not visible to the test client) and
the only indication of an AssertionError or other exception will be a
500 status code response to the test client. See the :attr:`testing`
attribute. For example::
app.testing = True
client = app.test_client()
The test client can be used in a ``with`` block to defer the closing down
of the context until the end of the ``with`` block. This is useful if
you want to access the context locals for testing::
with app.test_client() as c:
rv = c.get('/?vodka=42')
assert request.args['vodka'] == '42'
Additionally, you may pass optional keyword arguments that will then
be passed to the application's :attr:`test_client_class` constructor.
For example::
from flask.testing import FlaskClient
class CustomClient(FlaskClient):
def __init__(self, *args, **kwargs):
self._authentication = kwargs.pop("authentication")
super(CustomClient,self).__init__( *args, **kwargs)
app.test_client_class = CustomClient
client = app.test_client(authentication='Basic ....')
See :class:`~flask.testing.FlaskClient` for more information.
.. versionchanged:: 0.4
added support for ``with`` block usage for the client.
.. versionadded:: 0.7
The `use_cookies` parameter was added as well as the ability
to override the client to be used by setting the
:attr:`test_client_class` attribute.
.. versionchanged:: 0.11
Added `**kwargs` to support passing additional keyword arguments to
the constructor of :attr:`test_client_class`.
"""
cls = self.test_client_class
if cls is None:
from .testing import FlaskClient as cls
return cls( # type: ignore
self, self.response_class, use_cookies=use_cookies, **kwargs
)
def test_cli_runner(self, **kwargs: t.Any) -> FlaskCliRunner:
"""Create a CLI runner for testing CLI commands.
See :ref:`testing-cli`.
Returns an instance of :attr:`test_cli_runner_class`, by default
:class:`~flask.testing.FlaskCliRunner`. The Flask app object is
passed as the first argument.
.. versionadded:: 1.0
"""
cls = self.test_cli_runner_class
if cls is None:
from .testing import FlaskCliRunner as cls
return cls(self, **kwargs) # type: ignore
def handle_http_exception(
self, ctx: AppContext, e: HTTPException
) -> HTTPException | ft.ResponseReturnValue:
"""Handles an HTTP exception. By default this will invoke the
registered error handlers and fall back to returning the
exception as response.
.. versionchanged:: 1.0.3
``RoutingException``, used internally for actions such as
slash redirects during routing, is not passed to error
handlers.
.. versionchanged:: 1.0
Exceptions are looked up by code *and* by MRO, so
``HTTPException`` subclasses can be handled with a catch-all
handler for the base ``HTTPException``.
.. versionadded:: 0.3
"""
# Proxy exceptions don't have error codes. We want to always return
# those unchanged as errors
if e.code is None:
return e
# RoutingExceptions are used internally to trigger routing
# actions, such as slash redirects raising RequestRedirect. They
# are not raised or handled in user code.
if isinstance(e, RoutingException):
return e
handler = self._find_error_handler(e, ctx.request.blueprints)
if handler is None:
return e
return self.ensure_sync(handler)(e) # type: ignore[no-any-return]
def handle_user_exception(
self, ctx: AppContext, e: Exception
) -> HTTPException | ft.ResponseReturnValue:
"""This method is called whenever an exception occurs that
should be handled. A special case is :class:`~werkzeug
.exceptions.HTTPException` which is forwarded to the
:meth:`handle_http_exception` method. This function will either
return a response value or reraise the exception with the same
traceback.
.. versionchanged:: 1.0
Key errors raised from request data like ``form`` show the
bad key in debug mode rather than a generic bad request
message.
.. versionadded:: 0.7
"""
if isinstance(e, BadRequestKeyError) and (
self.debug or self.config["TRAP_BAD_REQUEST_ERRORS"]
):
e.show_exception = True
if isinstance(e, HTTPException) and not self.trap_http_exception(e):
return self.handle_http_exception(ctx, e)
handler = self._find_error_handler(e, ctx.request.blueprints)
if handler is None:
raise
return self.ensure_sync(handler)(e) # type: ignore[no-any-return]
def handle_exception(self, ctx: AppContext, e: Exception) -> Response:
"""Handle an exception that did not have an error handler
associated with it, or that was raised from an error handler.
This always causes a 500 ``InternalServerError``.
Always sends the :data:`got_request_exception` signal.
If :data:`PROPAGATE_EXCEPTIONS` is ``True``, such as in debug
mode, the error will be re-raised so that the debugger can
display it. Otherwise, the original exception is logged, and
an :exc:`~werkzeug.exceptions.InternalServerError` is returned.
If an error handler is registered for ``InternalServerError`` or
``500``, it will be used. For consistency, the handler will
always receive the ``InternalServerError``. The original
unhandled exception is available as ``e.original_exception``.
.. versionchanged:: 1.1.0
Always passes the ``InternalServerError`` instance to the
handler, setting ``original_exception`` to the unhandled
error.
.. versionchanged:: 1.1.0
``after_request`` functions and other finalization is done
even for the default 500 response when there is no handler.
.. versionadded:: 0.3
"""
exc_info = sys.exc_info()
got_request_exception.send(self, _async_wrapper=self.ensure_sync, exception=e)
propagate = self.config["PROPAGATE_EXCEPTIONS"]
if propagate is None:
propagate = self.testing or self.debug
if propagate:
# Re-raise if called with an active exception, otherwise
# raise the passed in exception.
if exc_info[1] is e:
raise
raise e
self.log_exception(ctx, exc_info)
server_error: InternalServerError | ft.ResponseReturnValue
server_error = InternalServerError(original_exception=e)
handler = self._find_error_handler(server_error, ctx.request.blueprints)
if handler is not None:
server_error = self.ensure_sync(handler)(server_error)
return self.finalize_request(ctx, server_error, from_error_handler=True)
def log_exception(
self,
ctx: AppContext,
exc_info: tuple[type, BaseException, TracebackType] | tuple[None, None, None],
) -> None:
"""Logs an exception. This is called by :meth:`handle_exception`
if debugging is disabled and right before the handler is called.
The default implementation logs the exception as error on the
:attr:`logger`.
.. versionadded:: 0.8
"""
self.logger.error(
f"Exception on {ctx.request.path} [{ctx.request.method}]", exc_info=exc_info
)
def dispatch_request(self, ctx: AppContext) -> ft.ResponseReturnValue:
"""Does the request dispatching. Matches the URL and returns the
return value of the view or error handler. This does not have to
be a response object. In order to convert the return value to a
proper response object, call :func:`make_response`.
.. versionchanged:: 0.7
This no longer does the exception handling, this code was
moved to the new :meth:`full_dispatch_request`.
"""
req = ctx.request
if req.routing_exception is not None:
self.raise_routing_exception(req)
rule: Rule = req.url_rule # type: ignore[assignment]
# if we provide automatic options for this URL and the
# request came with the OPTIONS method, reply automatically
if (
getattr(rule, "provide_automatic_options", False)
and req.method == "OPTIONS"
):
return self.make_default_options_response(ctx)
# otherwise dispatch to the handler for that endpoint
view_args: dict[str, t.Any] = req.view_args # type: ignore[assignment]
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args) # type: ignore[no-any-return]
def full_dispatch_request(self, ctx: AppContext) -> Response:
"""Dispatches the request and on top of that performs request
pre and postprocessing as well as HTTP exception catching and
error handling.
.. versionadded:: 0.7
"""
if not self._got_first_request and self.should_ignore_error is not None:
import warnings
warnings.warn(
"The 'should_ignore_error' method is deprecated and will"
" be removed in Flask 3.3. Handle errors as needed in"
" teardown handlers instead.",
DeprecationWarning,
stacklevel=1,
)
self._got_first_request = True
try:
request_started.send(self, _async_wrapper=self.ensure_sync)
rv = self.preprocess_request(ctx)
if rv is None:
rv = self.dispatch_request(ctx)
except Exception as e:
rv = self.handle_user_exception(ctx, e)
return self.finalize_request(ctx, rv)
def finalize_request(
self,
ctx: AppContext,
rv: ft.ResponseReturnValue | HTTPException,
from_error_handler: bool = False,
) -> Response:
"""Given the return value from a view function this finalizes
the request by converting it into a response and invoking the
postprocessing functions. This is invoked for both normal
request dispatching as well as error handlers.
Because this means that it might be called as a result of a
failure a special safe mode is available which can be enabled
with the `from_error_handler` flag. If enabled, failures in
response processing will be logged and otherwise ignored.
:internal:
"""
response = self.make_response(rv)
try:
response = self.process_response(ctx, response)
request_finished.send(
self, _async_wrapper=self.ensure_sync, response=response
)
except Exception:
if not from_error_handler:
raise
self.logger.exception(
"Request finalizing failed with an error while handling an error"
)
return response
def make_default_options_response(self, ctx: AppContext) -> Response:
"""This method is called to create the default ``OPTIONS`` response.
This can be changed through subclassing to change the default
behavior of ``OPTIONS`` responses.
.. versionadded:: 0.7
"""
methods = ctx.url_adapter.allowed_methods() # type: ignore[union-attr]
rv = self.response_class()
rv.allow.update(methods)
return rv
def ensure_sync(self, func: t.Callable[..., t.Any]) -> t.Callable[..., t.Any]:
"""Ensure that the function is synchronous for WSGI workers.
Plain ``def`` functions are returned as-is. ``async def``
functions are wrapped to run and wait for the response.
Override this method to change how the app runs async views.
.. versionadded:: 2.0
"""
if iscoroutinefunction(func):
return self.async_to_sync(func)
return func
def async_to_sync(
self, func: t.Callable[..., t.Coroutine[t.Any, t.Any, t.Any]]
) -> t.Callable[..., t.Any]:
"""Return a sync function that will run the coroutine function.
.. code-block:: python
result = app.async_to_sync(func)(*args, **kwargs)
Override this method to change how the app converts async code
to be synchronously callable.
.. versionadded:: 2.0
"""
try:
from asgiref.sync import async_to_sync as asgiref_async_to_sync
except ImportError:
raise RuntimeError(
"Install Flask with the 'async' extra in order to use async views."
) from None
return asgiref_async_to_sync(func)
def url_for(
self,
/,
endpoint: str,
*,
_anchor: str | None = None,
_method: str | None = None,
_scheme: str | None = None,
_external: bool | None = None,
**values: t.Any,
) -> str:
"""Generate a URL to the given endpoint with the given values.
This is called by :func:`flask.url_for`, and can be called
directly as well.
An *endpoint* is the name of a URL rule, usually added with
:meth:`@app.route() <route>`, and usually the same name as the
view function. A route defined in a :class:`~flask.Blueprint`
will prepend the blueprint's name separated by a ``.`` to the
endpoint.
In some cases, such as email messages, you want URLs to include
the scheme and domain, like ``https://example.com/hello``. When
not in an active request, URLs will be external by default, but
this requires setting :data:`SERVER_NAME` so Flask knows what
domain to use. :data:`APPLICATION_ROOT` and
:data:`PREFERRED_URL_SCHEME` should also be configured as
needed. This config is only used when not in an active request.
Functions can be decorated with :meth:`url_defaults` to modify
keyword arguments before the URL is built.
If building fails for some reason, such as an unknown endpoint
or incorrect values, the app's :meth:`handle_url_build_error`
method is called. If that returns a string, that is returned,
otherwise a :exc:`~werkzeug.routing.BuildError` is raised.
:param endpoint: The endpoint name associated with the URL to
generate. If this starts with a ``.``, the current blueprint
name (if any) will be used.
:param _anchor: If given, append this as ``#anchor`` to the URL.
:param _method: If given, generate the URL associated with this
method for the endpoint.
:param _scheme: If given, the URL will have this scheme if it
is external.
:param _external: If given, prefer the URL to be internal
(False) or require it to be external (True). External URLs
include the scheme and domain. When not in an active
request, URLs are external by default.
:param values: Values to use for the variable parts of the URL
rule. Unknown keys are appended as query string arguments,
like ``?a=b&c=d``.
.. versionadded:: 2.2
Moved from ``flask.url_for``, which calls this method.
"""
if (ctx := _cv_app.get(None)) is not None and ctx.has_request:
url_adapter = ctx.url_adapter
blueprint_name = ctx.request.blueprint
# If the endpoint starts with "." and the request matches a
# blueprint, the endpoint is relative to the blueprint.
if endpoint[:1] == ".":
if blueprint_name is not None:
endpoint = f"{blueprint_name}{endpoint}"
else:
endpoint = endpoint[1:]
# When in a request, generate a URL without scheme and
# domain by default, unless a scheme is given.
if _external is None:
_external = _scheme is not None
else:
# If called by helpers.url_for, an app context is active,
# use its url_adapter. Otherwise, app.url_for was called
# directly, build an adapter.
if ctx is not None:
url_adapter = ctx.url_adapter
else:
url_adapter = self.create_url_adapter(None)
if url_adapter is None:
raise RuntimeError(
"Unable to build URLs outside an active request"
" without 'SERVER_NAME' configured. Also configure"
" 'APPLICATION_ROOT' and 'PREFERRED_URL_SCHEME' as"
" needed."
)
# When outside a request, generate a URL with scheme and
# domain by default.
if _external is None:
_external = True
# It is an error to set _scheme when _external=False, in order
# to avoid accidental insecure URLs.
if _scheme is not None and not _external:
raise ValueError("When specifying '_scheme', '_external' must be True.")
self.inject_url_defaults(endpoint, values)
try:
rv = url_adapter.build( # type: ignore[union-attr]
endpoint,
values,
method=_method,
url_scheme=_scheme,
force_external=_external,
)
except BuildError as error:
values.update(
_anchor=_anchor, _method=_method, _scheme=_scheme, _external=_external
)
return self.handle_url_build_error(error, endpoint, values)
if _anchor is not None:
_anchor = _url_quote(_anchor, safe="%!#$&'()*+,/:;=?@")
rv = f"{rv}#{_anchor}"
return rv
def make_response(self, rv: ft.ResponseReturnValue) -> Response:
"""Convert the return value from a view function to an instance of
:attr:`response_class`.
:param rv: the return value from the view function. The view function
must return a response. Returning ``None``, or the view ending
without returning, is not allowed. The following types are allowed
for ``view_rv``:
``str``
A response object is created with the string encoded to UTF-8
as the body.
``bytes``
A response object is created with the bytes as the body.
``dict``
Converted to a JSON response.
``list``
Converted to a JSON response.
``generator`` or ``iterator``
A generator that returns ``str`` or ``bytes`` to be
streamed as the response.
``tuple``
Either ``(body, status, headers)``, ``(body, status)``, or
``(body, headers)``, where ``body`` is any of the other types
allowed here, ``status`` is a string or an integer, and
``headers`` is a dictionary or a list of ``(key, value)``
tuples. If ``body`` is a :attr:`response_class` instance,
``status`` overwrites the exiting value and ``headers`` are
extended.
:attr:`response_class`
The object is returned unchanged.
other :class:`~werkzeug.wrappers.Response` class
The object is coerced to :attr:`response_class`.
:func:`callable`
The function is called as a WSGI application. The result is
used to create a response object.
.. versionchanged:: 2.2
A generator will be converted to a streaming response.
A list will be converted to a JSON response.
.. versionchanged:: 1.1
A dict will be converted to a JSON response.
.. versionchanged:: 0.9
Previously a tuple was interpreted as the arguments for the
response object.
"""
status: int | None = None
headers: HeadersValue | None = None
# unpack tuple returns
if isinstance(rv, tuple):
len_rv = len(rv)
# a 3-tuple is unpacked directly
if len_rv == 3:
rv, status, headers = rv # type: ignore[misc]
# decide if a 2-tuple has status or headers
elif len_rv == 2:
if isinstance(rv[1], (Headers, dict, tuple, list)):
rv, headers = rv # pyright: ignore
else:
rv, status = rv # type: ignore[assignment,misc]
# other sized tuples are not allowed
else:
raise TypeError(
"The view function did not return a valid response tuple."
" The tuple must have the form (body, status, headers),"
" (body, status), or (body, headers)."
)
# the body must not be None
if rv is None:
raise TypeError(
f"The view function for {request.endpoint!r} did not"
" return a valid response. The function either returned"
" None or ended without a return statement."
)
# make sure the body is an instance of the response class
if not isinstance(rv, self.response_class):
if isinstance(rv, (str, bytes, bytearray)) or isinstance(rv, cabc.Iterator):
# let the response class set the status and headers instead of
# waiting to do it manually, so that the class can handle any
# special logic
rv = self.response_class(
rv, # pyright: ignore
status=status,
headers=headers, # type: ignore[arg-type]
)
status = headers = None
elif isinstance(rv, (dict, list)):
rv = self.json.response(rv)
elif isinstance(rv, BaseResponse) or callable(rv):
# evaluate a WSGI callable, or coerce a different response
# class to the correct type
try:
rv = self.response_class.force_type(
rv, # type: ignore[arg-type]
request.environ,
)
except TypeError as e:
raise TypeError(
f"{e}\nThe view function did not return a valid"
" response. The return type must be a string,"
" dict, list, tuple with headers or status,"
" Response instance, or WSGI callable, but it"
f" was a {type(rv).__name__}."
).with_traceback(sys.exc_info()[2]) from None
else:
raise TypeError(
"The view function did not return a valid"
" response. The return type must be a string,"
" dict, list, tuple with headers or status,"
" Response instance, or WSGI callable, but it was a"
f" {type(rv).__name__}."
)
rv = t.cast(Response, rv)
# prefer the status if it was provided
if status is not None:
if isinstance(status, (str, bytes, bytearray)):
rv.status = status
else:
rv.status_code = status
# extend existing headers with provided headers
if headers:
rv.headers.update(headers)
return rv
def preprocess_request(self, ctx: AppContext) -> ft.ResponseReturnValue | None:
"""Called before the request is dispatched. Calls
:attr:`url_value_preprocessors` registered with the app and the
current blueprint (if any). Then calls :attr:`before_request_funcs`
registered with the app and the blueprint.
If any :meth:`before_request` handler returns a non-None value, the
value is handled as if it was the return value from the view, and
further request handling is stopped.
"""
req = ctx.request
names = (None, *reversed(req.blueprints))
loopIteratorI = __import__("builtins").iter(names)
while True:
try:
name = __import__("builtins").next(loopIteratorI)
except __import__("builtins").StopIteration:
break
if name in self.url_value_preprocessors:
loopIteratorB = __import__("builtins").iter(self.url_value_preprocessors[name])
while True:
try:
url_func = __import__("builtins").next(loopIteratorB)
except __import__("builtins").StopIteration:
break
url_func(req.endpoint, req.view_args)
loopIteratorJ = __import__("builtins").iter(names)
while True:
try:
name = __import__("builtins").next(loopIteratorJ)
except __import__("builtins").StopIteration:
break
if name in self.before_request_funcs:
loopIteratorC = __import__("builtins").iter(self.before_request_funcs[name])
while True:
try:
before_func = __import__("builtins").next(loopIteratorC)
except __import__("builtins").StopIteration:
break
rv = self.ensure_sync(before_func)()
if rv is not None:
return rv # type: ignore[no-any-return]
return None
def process_response(self, ctx: AppContext, response: Response) -> Response:
"""Can be overridden in order to modify the response object
before it's sent to the WSGI server. By default this will
call all the :meth:`after_request` decorated functions.
.. versionchanged:: 0.5
As of Flask 0.5 the functions registered for after request
execution are called in reverse order of registration.
:param response: a :attr:`response_class` object.
:return: a new response object or the same, has to be an
instance of :attr:`response_class`.
"""
loopIteratorD = __import__("builtins").iter(ctx._after_request_functions)
while True:
try:
func = __import__("builtins").next(loopIteratorD)
except __import__("builtins").StopIteration:
break
response = self.ensure_sync(func)(response)
loopIteratorK = __import__("builtins").iter(chain(ctx.request.blueprints, (None,)))
while True:
try:
name = __import__("builtins").next(loopIteratorK)
except __import__("builtins").StopIteration:
break
if name in self.after_request_funcs:
loopIteratorE = __import__("builtins").iter(reversed(self.after_request_funcs[name]))
while True:
try:
func = __import__("builtins").next(loopIteratorE)
except __import__("builtins").StopIteration:
break
response = self.ensure_sync(func)(response)
if not self.session_interface.is_null_session(ctx._get_session()):
self.session_interface.save_session(self, ctx._get_session(), response)
return response
def do_teardown_request(
self, ctx: AppContext, exc: BaseException | None = None
) -> None:
"""Called after the request is dispatched and the response is finalized,
right before the request context is popped. Called by
:meth:`.AppContext.pop`.
This calls all functions decorated with :meth:`teardown_request`, and
:meth:`Blueprint.teardown_request` if a blueprint handled the request.
Finally, the :data:`request_tearing_down` signal is sent.
:param exc: An unhandled exception raised while dispatching the request.
Passed to each teardown function.
.. versionchanged:: 3.2
All callbacks are called rather than stopping on the first error.
.. versionchanged:: 0.9
Added the ``exc`` argument.
"""
collect_errors = _CollectErrors()
loopIteratorL = __import__("builtins").iter(chain(ctx.request.blueprints, (None,)))
while True:
try:
name = __import__("builtins").next(loopIteratorL)
except __import__("builtins").StopIteration:
break
if name in self.teardown_request_funcs:
loopIteratorF = __import__("builtins").iter(reversed(self.teardown_request_funcs[name]))
while True:
try:
func = __import__("builtins").next(loopIteratorF)
except __import__("builtins").StopIteration:
break
with collect_errors:
self.ensure_sync(func)(exc)
with collect_errors:
request_tearing_down.send(self, _async_wrapper=self.ensure_sync, exc=exc)
collect_errors.raise_any("Errors during request teardown")
def do_teardown_appcontext(
self, ctx: AppContext, exc: BaseException | None = None
) -> None:
"""Called right before the application context is popped. Called by
:meth:`.AppContext.pop`.
This calls all functions decorated with :meth:`teardown_appcontext`.
Then the :data:`appcontext_tearing_down` signal is sent.
:param exc: An unhandled exception raised while the context was active.
Passed to each teardown function.
.. versionchanged:: 3.2
All callbacks are called rather than stopping on the first error.
.. versionadded:: 0.9
"""
collect_errors = _CollectErrors()
loopIteratorG = __import__("builtins").iter(reversed(self.teardown_appcontext_funcs))
while True:
try:
func = __import__("builtins").next(loopIteratorG)
except __import__("builtins").StopIteration:
break
with collect_errors:
self.ensure_sync(func)(exc)
with collect_errors:
appcontext_tearing_down.send(self, _async_wrapper=self.ensure_sync, exc=exc)
collect_errors.raise_any("Errors during app teardown")
def app_context(self) -> AppContext:
"""Create an :class:`.AppContext`. When the context is pushed,
:data:`.current_app` and :data:`.g` become available.
A context is automatically pushed when handling each request, and when
running any ``flask`` CLI command. Use this as a ``with`` block to
manually push a context outside of those situations, such as during
setup or testing.
.. code-block:: python
with app.app_context():
init_db()
See :doc:`/appcontext`.
.. versionadded:: 0.9
"""
return AppContext(self)
def request_context(self, environ: WSGIEnvironment) -> AppContext:
"""Create an :class:`.AppContext` with request information representing
the given WSGI environment. A context is automatically pushed when
handling each request. When the context is pushed, :data:`.request`,
:data:`.session`, :data:`g:, and :data:`.current_app` become available.
This method should not be used in your own code. Creating a valid WSGI
environ is not trivial. Use :meth:`test_request_context` to correctly
create a WSGI environ and request context instead.
See :doc:`/appcontext`.
:param environ: A WSGI environment.
"""
return AppContext.from_environ(self, environ)
def test_request_context(self, *args: t.Any, **kwargs: t.Any) -> AppContext:
"""Create an :class:`.AppContext` with request information created from
the given arguments. When the context is pushed, :data:`.request`,
:data:`.session`, :data:`g:, and :data:`.current_app` become available.
This is useful during testing to run a function that uses request data
without dispatching a full request. Use this as a ``with`` block to push
a context.
.. code-block:: python
with app.test_request_context(...):
generate_report()
See :doc:`/appcontext`.
Takes the same arguments as Werkzeug's
:class:`~werkzeug.test.EnvironBuilder`, with some defaults from
the application. See the linked Werkzeug docs for most of the
available arguments. Flask-specific behavior is listed here.
:param path: URL path being requested.
:param base_url: Base URL where the app is being served, which
``path`` is relative to. If not given, built from
:data:`PREFERRED_URL_SCHEME`, ``subdomain``, :data:`SERVER_NAME`,
and :data:`APPLICATION_ROOT`.
:param subdomain: Subdomain name to prepend to :data:`SERVER_NAME`.
:param url_scheme: Scheme to use instead of
:data:`PREFERRED_URL_SCHEME`.
:param data: The request body text or bytes,or a dict of form data.
:param json: If given, this is serialized as JSON and passed as
``data``. Also defaults ``content_type`` to
``application/json``.
:param args: Other positional arguments passed to
:class:`~werkzeug.test.EnvironBuilder`.
:param kwargs: Other keyword arguments passed to
:class:`~werkzeug.test.EnvironBuilder`.
"""
from .testing import EnvironBuilder
builder = EnvironBuilder(self, *args, **kwargs)
try:
environ = builder.get_environ()
finally:
builder.close()
return self.request_context(environ)
def wsgi_app(
self, environ: WSGIEnvironment, start_response: StartResponse
) -> cabc.Iterable[bytes]:
"""The actual WSGI application. This is not implemented in
:meth:`__call__` so that middlewares can be applied without
losing a reference to the app object. Instead of doing this::
app = MyMiddleware(app)
It's a better idea to do this instead::
app.wsgi_app = MyMiddleware(app.wsgi_app)
Then you still have the original application object around and
can continue to call methods on it.
.. versionchanged:: 0.7
Teardown events for the request and app contexts are called
even if an unhandled error occurs. Other events may not be
called depending on when an error occurs during dispatch.
:param environ: A WSGI environment.
:param start_response: A callable accepting a status code,
a list of headers, and an optional exception context to
start the response.
"""
ctx = self.request_context(environ)
error: BaseException | None = None
try:
try:
ctx.push()
response = self.full_dispatch_request(ctx)
except Exception as e:
error = e
response = self.handle_exception(ctx, e)
except:
error = sys.exc_info()[1]
raise
return response(environ, start_response)
finally:
if "werkzeug.debug.preserve_context" in environ:
environ["werkzeug.debug.preserve_context"](ctx)
if (
error is not None
and self.should_ignore_error is not None
and self.should_ignore_error(error)
):
error = None
ctx.pop(error)
def __call__(
self, environ: WSGIEnvironment, start_response: StartResponse
) -> cabc.Iterable[bytes]:
"""The WSGI server calls the Flask application object as the
WSGI application. This calls :meth:`wsgi_app`, which can be
wrapped to apply middleware.
"""
return self.wsgi_app(environ, start_response)