Source code
from __future__ import annotations
import os
import typing as t
from collections import defaultdict
from functools import update_wrapper
from .. import typing as ft
from .scaffold import _endpoint_from_view_func
from .scaffold import _sentinel
from .scaffold import Scaffold
from .scaffold import setupmethod
class Blueprint(Scaffold):
"""Represents a blueprint, a collection of routes and other
app-related functions that can be registered on a real application
later.
A blueprint is an object that allows defining application functions
without requiring an application object ahead of time. It uses the
same decorators as :class:`~flask.Flask`, but defers the need for an
application by recording them for later registration.
Decorating a function with a blueprint creates a deferred function
that is called with :class:`~flask.blueprints.BlueprintSetupState`
when the blueprint is registered on an application.
See :doc:`/blueprints` for more information.
:param name: The name of the blueprint. Will be prepended to each
endpoint name.
:param import_name: The name of the blueprint package, usually
``__name__``. This helps locate the ``root_path`` for the
blueprint.
:param static_folder: A folder with static files that should be
served by the blueprint's static route. The path is relative to
the blueprint's root path. Blueprint static files are disabled
by default.
:param static_url_path: The url to serve static files from.
Defaults to ``static_folder``. If the blueprint does not have
a ``url_prefix``, the app's static route will take precedence,
and the blueprint's static files won't be accessible.
:param template_folder: A folder with templates that should be added
to the app's template search path. The path is relative to the
blueprint's root path. Blueprint templates are disabled by
default. Blueprint templates have a lower precedence than those
in the app's templates folder.
:param url_prefix: A path to prepend to all of the blueprint's URLs,
to make them distinct from the rest of the app's routes.
:param subdomain: A subdomain that blueprint routes will match on by
default.
:param url_defaults: A dict of default values that blueprint routes
will receive by default.
:param root_path: By default, the blueprint will automatically set
this based on ``import_name``. In certain situations this
automatic detection can fail, so the path can be specified
manually instead.
.. versionchanged:: 1.1.0
Blueprints have a ``cli`` group to register nested CLI commands.
The ``cli_group`` parameter controls the name of the group under
the ``flask`` command.
.. versionadded:: 0.7
"""
_got_registered_once = False
def __init__(
self,
name: str,
import_name: str,
static_folder: str | os.PathLike[str] | None = None,
static_url_path: str | None = None,
template_folder: str | os.PathLike[str] | None = None,
url_prefix: str | None = None, subdomain: str | None = None, url_defaults: dict[str, t.Any] | None = None,
root_path: str | None = None, cli_group: str | None = _sentinel, # type: ignore[assignment]
):
super().__init__(
import_name=import_name,
static_folder=static_folder,
static_url_path=static_url_path,
template_folder=template_folder, root_path=root_path,
)
if not name:
raise ValueError("'name' may not be empty.")
if "." in name:
raise ValueError("'name' may not contain a dot '.' character.")
self.name = name
self.url_prefix = url_prefix
self.subdomain = subdomain
self.deferred_functions: list[DeferredSetupFunction] = []
if url_defaults is None:
url_defaults = {}
self.url_values_defaults = url_defaults
self.cli_group = cli_group
self._blueprints: list[tuple[Blueprint, dict[str, t.Any]]] = []
def _check_setup_finished(self, f_name: str) -> None:
if self._got_registered_once:
raise AssertionError( f"The setup method '{f_name}' can no longer be called on the blueprint" f" '{self.name}'. It has already been registered at least once, any" " changes will not be applied consistently.\n" "Make sure all imports, decorators, functions, etc. needed to set up" " the blueprint are done before registering it." )
@setupmethod
def record(self, func: DeferredSetupFunction) -> None:
"""Registers a function that is called when the blueprint is
registered on the application. This function is called with the
state as argument as returned by the :meth:`make_setup_state`
method.
"""
self.deferred_functions.append(func)
@setupmethod
def record_once(self, func: DeferredSetupFunction) -> None:
"""Works like :meth:`record` but wraps the function in another
function that will ensure the function is only called once. If the
blueprint is registered a second time on the application, the
function passed is not called.
"""
def wrapper(state: BlueprintSetupState) -> None:
if state.first_registration:
func(state)
self.record(update_wrapper(wrapper, func))
def make_setup_state(
self, app: App, options: dict[str, t.Any], first_registration: bool = False
) -> BlueprintSetupState:
"""Creates an instance of :meth:`~flask.blueprints.BlueprintSetupState`
object that is later passed to the register callback functions.
Subclasses can override this to return a subclass of the setup state.
"""
return BlueprintSetupState(self, app, options, first_registration)
@setupmethod
def register_blueprint(self, blueprint: Blueprint, **options: t.Any) -> None:
"""Register a :class:`~flask.Blueprint` on this blueprint. Keyword
arguments passed to this method will override the defaults set
on the blueprint.
.. versionchanged:: 2.0.1
The ``name`` option can be used to change the (pre-dotted)
name the blueprint is registered with. This allows the same
blueprint to be registered multiple times with unique names
for ``url_for``.
.. versionadded:: 2.0
"""
if blueprint is self:
raise ValueError("Cannot register a blueprint on itself")
self._blueprints.append((blueprint, options))
def register(self, app: App, options: dict[str, t.Any]) -> None:
"""Called by :meth:`Flask.register_blueprint` to register all
views and callbacks registered on the blueprint with the
application. Creates a :class:`.BlueprintSetupState` and calls
each :meth:`record` callback with it.
:param app: The application this blueprint is being registered
with.
:param options: Keyword arguments forwarded from
:meth:`~Flask.register_blueprint`.
.. versionchanged:: 2.3
Nested blueprints now correctly apply subdomains.
.. versionchanged:: 2.1
Registering the same blueprint with the same name multiple
times is an error.
.. versionchanged:: 2.0.1
Nested blueprints are registered with their dotted name.
This allows different blueprints with the same name to be
nested at different locations.
.. versionchanged:: 2.0.1
The ``name`` option can be used to change the (pre-dotted)
name the blueprint is registered with. This allows the same
blueprint to be registered multiple times with unique names
for ``url_for``.
"""
name_prefix = options.get("name_prefix", "")
self_name = options.get("name", self.name)
name = f"{name_prefix}.{self_name}".lstrip(".")
if name in app.blueprints:
bp_desc = "this" if app.blueprints[name] is self else "a different"
existing_at = f" '{name}'" if self_name != name else ""
raise ValueError(
f"The name '{self_name}' is already registered for"
f" {bp_desc} blueprint{existing_at}. Use 'name=' to" f" provide a unique name."
)
first_bp_registration = not any(bp is self for bp in app.blueprints.values())
first_name_registration = name not in app.blueprints
app.blueprints[name] = self
self._got_registered_once = True
state = self.make_setup_state(app, options, first_bp_registration)
if self.has_static_folder:
state.add_url_rule(
f"{self.static_url_path}/<path:filename>",
view_func=self.send_static_file, # type: ignore[attr-defined]
endpoint="static", )
# Merge blueprint data into parent.
if first_bp_registration or first_name_registration:
self._merge_blueprint_funcs(app, name)
for deferred in self.deferred_functions:
deferred(state)
cli_resolved_group = options.get("cli_group", self.cli_group)
if self.cli.commands:
if cli_resolved_group is None:
app.cli.commands.update(self.cli.commands)
elif cli_resolved_group is _sentinel:
self.cli.name = name
app.cli.add_command(self.cli)
else:
self.cli.name = cli_resolved_group
app.cli.add_command(self.cli)
for blueprint, bp_options in self._blueprints:
bp_options = bp_options.copy()
bp_url_prefix = bp_options.get("url_prefix")
bp_subdomain = bp_options.get("subdomain")
if bp_subdomain is None:
bp_subdomain = blueprint.subdomain
if state.subdomain is not None and bp_subdomain is not None:
bp_options["subdomain"] = bp_subdomain + "." + state.subdomain
elif bp_subdomain is not None:
bp_options["subdomain"] = bp_subdomain
elif state.subdomain is not None:
bp_options["subdomain"] = state.subdomain
if bp_url_prefix is None:
bp_url_prefix = blueprint.url_prefix
if state.url_prefix is not None and bp_url_prefix is not None:
bp_options["url_prefix"] = ( state.url_prefix.rstrip("/") + "/" + bp_url_prefix.lstrip("/")
)
elif bp_url_prefix is not None:
bp_options["url_prefix"] = bp_url_prefix
elif state.url_prefix is not None:
bp_options["url_prefix"] = state.url_prefix
bp_options["name_prefix"] = name
blueprint.register(app, bp_options)
def _merge_blueprint_funcs(self, app: App, name: str) -> None:
def extend( bp_dict: dict[ft.AppOrBlueprintKey, list[t.Any]],
parent_dict: dict[ft.AppOrBlueprintKey, list[t.Any]], ) -> None:
for key, values in bp_dict.items():
key = name if key is None else f"{name}.{key}"
parent_dict[key].extend(values)
for key, value in self.error_handler_spec.items():
key = name if key is None else f"{name}.{key}"
value = defaultdict(
dict,
{ code: {exc_class: func for exc_class, func in code_values.items()}
for code, code_values in value.items()
}, )
app.error_handler_spec[key] = value
for endpoint, func in self.view_functions.items():
app.view_functions[endpoint] = func
extend(self.before_request_funcs, app.before_request_funcs)
extend(self.after_request_funcs, app.after_request_funcs)
extend(
self.teardown_request_funcs,
app.teardown_request_funcs,
)
extend(self.url_default_functions, app.url_default_functions)
extend(self.url_value_preprocessors, app.url_value_preprocessors)
extend(self.template_context_processors, app.template_context_processors)
@setupmethod
def add_url_rule( self,
rule: str,
endpoint: str | None = None, view_func: ft.RouteCallable | None = None,
provide_automatic_options: bool | None = None, **options: t.Any,
) -> None:
"""Register a URL rule with the blueprint. See :meth:`.Flask.add_url_rule` for
full documentation.
The URL rule is prefixed with the blueprint's URL prefix. The endpoint name,
used with :func:`url_for`, is prefixed with the blueprint's name.
"""
if endpoint and "." in endpoint:
raise ValueError("'endpoint' may not contain a dot '.' character.")
if view_func and hasattr(view_func, "__name__") and "." in view_func.__name__:
raise ValueError("'view_func' name may not contain a dot '.' character.")
self.record( lambda s: s.add_url_rule( rule,
endpoint,
view_func, provide_automatic_options=provide_automatic_options, **options,
)
)
@t.overload
def app_template_filter(self, name: T_template_filter) -> T_template_filter: ...
@t.overload
def app_template_filter( self, name: str | None = None
) -> t.Callable[[T_template_filter], T_template_filter]: ...
@setupmethod
def app_template_filter( self, name: T_template_filter | str | None = None
) -> T_template_filter | t.Callable[[T_template_filter], T_template_filter]:
"""Decorate a function to register it as a custom Jinja filter. The name
is optional. The decorator may be used without parentheses.
The :meth:`add_app_template_filter` method may be used to register a
function later rather than decorating.
The filter is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.template_filter`.
:param name: The name to register the filter as. If not given, uses the
function's name.
"""
if callable(name):
self.add_app_template_filter(name)
return name
def decorator(f: T_template_filter) -> T_template_filter:
self.add_app_template_filter(f, name=name)
return f
return decorator
@setupmethod
def add_app_template_filter( self, f: ft.TemplateFilterCallable, name: str | None = None ) -> None:
"""Register a function to use as a custom Jinja filter.
The :meth:`app_template_filter` decorator can be used to register a
function by decorating instead.
The filter is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.add_template_filter`.
:param f: The function to register.
:param name: The name to register the filter as. If not given, uses the
function's name.
"""
def register_template_filter(state: BlueprintSetupState) -> None:
state.app.add_template_filter(f, name=name)
self.record_once(register_template_filter)
@t.overload
def app_template_test(self, name: T_template_test) -> T_template_test: ...
@t.overload
def app_template_test(
self, name: str | None = None
) -> t.Callable[[T_template_test], T_template_test]: ...
@setupmethod
def app_template_test(
self, name: T_template_test | str | None = None ) -> T_template_test | t.Callable[[T_template_test], T_template_test]:
"""Decorate a function to register it as a custom Jinja test. The name
is optional. The decorator may be used without parentheses.
The :meth:`add_app_template_test` method may be used to register a
function later rather than decorating.
The test is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.template_test`.
:param name: The name to register the filter as. If not given, uses the
function's name.
.. versionadded:: 0.10
"""
if callable(name):
self.add_app_template_test(name)
return name
def decorator(f: T_template_test) -> T_template_test:
self.add_app_template_test(f, name=name)
return f
return decorator
@setupmethod
def add_app_template_test(
self, f: ft.TemplateTestCallable, name: str | None = None ) -> None:
"""Register a function to use as a custom Jinja test.
The :meth:`app_template_test` decorator can be used to register a
function by decorating instead.
The test is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.add_template_test`.
:param f: The function to register.
:param name: The name to register the test as. If not given, uses the
function's name.
.. versionadded:: 0.10
"""
def register_template_test(state: BlueprintSetupState) -> None:
state.app.add_template_test(f, name=name)
self.record_once(register_template_test)
@t.overload
def app_template_global(self, name: T_template_global) -> T_template_global: ...
@t.overload
def app_template_global(
self, name: str | None = None
) -> t.Callable[[T_template_global], T_template_global]: ...
@setupmethod
def app_template_global( self, name: T_template_global | str | None = None
) -> T_template_global | t.Callable[[T_template_global], T_template_global]:
"""Decorate a function to register it as a custom Jinja global. The name
is optional. The decorator may be used without parentheses.
The :meth:`add_app_template_global` method may be used to register a
function later rather than decorating.
The global is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.template_global`.
:param name: The name to register the global as. If not given, uses the
function's name.
.. versionadded:: 0.10
"""
if callable(name):
self.add_app_template_global(name)
return name
def decorator(f: T_template_global) -> T_template_global:
self.add_app_template_global(f, name=name)
return f
return decorator
@setupmethod
def add_app_template_global( self, f: ft.TemplateGlobalCallable, name: str | None = None ) -> None:
"""Register a function to use as a custom Jinja global.
The :meth:`app_template_global` decorator can be used to register a function
by decorating instead.
The global is available in all templates, not only those under this
blueprint. Equivalent to :meth:`.Flask.add_template_global`.
:param f: The function to register.
:param name: The name to register the global as. If not given, uses the
function's name.
.. versionadded:: 0.10
"""
def register_template_global(state: BlueprintSetupState) -> None:
state.app.add_template_global(f, name=name)
self.record_once(register_template_global)
@setupmethod
def before_app_request(self, f: T_before_request) -> T_before_request:
"""Like :meth:`before_request`, but before every request, not only those handled
by the blueprint. Equivalent to :meth:`.Flask.before_request`.
"""
self.record_once(
lambda s: s.app.before_request_funcs.setdefault(None, []).append(f)
)
return f
@setupmethod
def after_app_request(self, f: T_after_request) -> T_after_request:
"""Like :meth:`after_request`, but after every request, not only those handled
by the blueprint. Equivalent to :meth:`.Flask.after_request`.
"""
self.record_once(
lambda s: s.app.after_request_funcs.setdefault(None, []).append(f) )
return f
@setupmethod
def teardown_app_request(self, f: T_teardown) -> T_teardown:
"""Like :meth:`teardown_request`, but after every request, not only those
handled by the blueprint. Equivalent to :meth:`.Flask.teardown_request`.
"""
self.record_once(
lambda s: s.app.teardown_request_funcs.setdefault(None, []).append(f) )
return f
@setupmethod
def app_context_processor( self, f: T_template_context_processor ) -> T_template_context_processor:
"""Like :meth:`context_processor`, but for templates rendered by every view, not
only by the blueprint. Equivalent to :meth:`.Flask.context_processor`.
"""
self.record_once( lambda s: s.app.template_context_processors.setdefault(None, []).append(f)
)
return f
@setupmethod
def app_errorhandler(
self, code: type[Exception] | int ) -> t.Callable[[T_error_handler], T_error_handler]:
"""Like :meth:`errorhandler`, but for every request, not only those handled by
the blueprint. Equivalent to :meth:`.Flask.errorhandler`.
"""
def decorator(f: T_error_handler) -> T_error_handler:
def from_blueprint(state: BlueprintSetupState) -> None:
state.app.errorhandler(code)(f)
self.record_once(from_blueprint)
return f
return decorator
@setupmethod
def app_url_value_preprocessor(
self, f: T_url_value_preprocessor ) -> T_url_value_preprocessor:
"""Like :meth:`url_value_preprocessor`, but for every request, not only those
handled by the blueprint. Equivalent to :meth:`.Flask.url_value_preprocessor`.
"""
self.record_once( lambda s: s.app.url_value_preprocessors.setdefault(None, []).append(f)
)
return f
@setupmethod
def app_url_defaults(self, f: T_url_defaults) -> T_url_defaults:
"""Like :meth:`url_defaults`, but for every request, not only those handled by
the blueprint. Equivalent to :meth:`.Flask.url_defaults`.
"""
self.record_once( lambda s: s.app.url_default_functions.setdefault(None, []).append(f)
)
return f