Help with extending an extension

[misilot]

Hello,

I am having a hard time wrapping my head around on how to best extend an existing extension.

So I want to use this extension (https://github.com/helloflask/bootstrap-flask) as the basis for our theming, for our different flask apps, so they have all have a common look, with same basic built in routes / templates.

So, for templates, it seems to work, but everything falls apart when I try to add url routes.

In my extension (ksul-bootstrap-flask) I have

ksul-bootstrap-flask\ksul-bootstrap-flask\__init__.py:

import flask
from flask_bootstrap import Bootstrap4
from flask import Blueprint, current_app, url_for

class KSULBootstrap4(Bootstrap4):
    static_folder = 'bootstrap4'


    def __init__(self, app=None):
        super().__init__(app)

    def init_app(self, app):        
        if not hasattr(app, 'extensions'):
            app.extensions = {}
        app.extensions['ksul-bootstrap'] = self
        
        blueprint = Blueprint('ksul-bootstrap', __name__, static_folder=f'static/{self.static_folder}',
                                    static_url_path=f'/ksul{app.static_url_path}',
                                    template_folder='templates')


        # blueprint.add_url_rule('/favicon.ico',
        #     redirect_to=url_for('static', filename='favicon.ico'))

        super().init_app(app=app)
        app.register_blueprint(blueprint)

In my application I have the following

from flask import Flask
from ksul_bootstrap_flask import KSULBootstrap4
from config import Config
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
import pymysql
pymysql.install_as_MySQLdb()

app = Flask(__name__)
bootstrap = KSULBootstrap4(app)
app.config.from_object(Config)
db = SQLAlchemy(app)
migrate = Migrate(app, db)

from app import routes, models

When I uncomment the add_url_rule lines above, I get the following error:

RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
the current application. To solve this, set up an application context
with app.app_context(). See the documentation for more information.

I've tried adding with app.app_context(): as per the documentation https://flask.palletsprojects.com/en/2.2.x/appcontext/, but then the app doesn't know anything about the site url, etc... so not quite sure what I am missing.

I'm using Flask 2.2.3

Thanks!
Tom

[davidism]

You can't call url_for outside an app context. If you need a context during set up, push one in a with block.

with app.app_context():
    setup stuff that needs a context

[misilot]

Thanks @davidism,

I have tried that

    def init_app(self, app):        
        if not hasattr(app, 'extensions'):
            app.extensions = {}
        app.extensions['ksul-bootstrap'] = self
        
        blueprint = Blueprint('ksul-bootstrap', __name__, static_folder=f'static/{self.static_folder}',
                                    static_url_path=f'/ksul{app.static_url_path}',
                                    template_folder='templates')


        with app.app_context():
            blueprint.add_url_rule('/favicon.ico',
                redirect_to=url_for('static', filename='favicon.ico'))

        super().init_app(app=app)
        app.register_blueprint(blueprint)

However, that presents me with the following error:

RuntimeError: Unable to build URLs outside an active request without 'SERVER_NAME' configured. Also configure 'APPLICATION_ROOT' and 'PREFERRED_URL_SCHEME' as needed.

I didn't think the extension would need to know this information this far down, and it would be provided by the application, no?

Thanks!

[misilot]

        @app.route('/favicon.ico')
        def favicon():
            print(app.static_path)

            return send_from_directory(os.path.join('ksul-bootstrap.static'),
                        'img/favicon.ico', mimetype='image/vnd.microsoft.icon')

This is getting be closer, but I can't seem to find out the path that will give me the static_path for the extension itself (installed via pip in a venv). If I do app.static_path it gives me the base application's static path, and app.extensions['ksul-bootstrap'].static_path doesn't exist.

[misilot]

I got it working the following

        @app.route('/favicon.ico')
        def favicon():
            return redirect(url_for('ksul-bootstrap.static', filename='img/favicon.ico'))

import flask
from flask_bootstrap import Bootstrap4
from flask import Blueprint, current_app, url_for, redirect

class KSULBootstrap4(Bootstrap4):
    # bootstrap_version = '4.6.2'
    # jquery_version = '3.5.1'
    # popper_version = '1.16.1'
    # bootstrap_css_integrity = 'sha384-xOolHFLEh07PJGoPkLv1IbcEPTNtaed2xpHsD9ESMhqIYd0nLMwNLD69Npy4HI+N'
    # bootstrap_js_integrity = 'sha384-+sLIOodYLS7CIrQpBjl+C7nPvqq+FbNUBDunl/OZv93DB7Ln/533i8e/mZXLi/P+'
    # jquery_integrity = 'sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj'
    # popper_integrity = 'sha384-9/reFTGAW83EW2RDu2S0VKaIzap3H66lZH81PoYlFhbGU+6BZp6G7niu735Sk7lN'
    # popper_name = 'popper.js'
    static_folder = 'bootstrap4'


    def __init__(self, app=None):
        super().__init__(app)

    def init_app(self, app):        

        if not hasattr(app, 'extensions'):
            app.extensions = {}
        app.extensions['ksul-bootstrap'] = self
        

        @app.route('/favicon.ico')
        def favicon():
            return redirect(url_for('ksul-bootstrap.static', filename='img/favicon.ico'))

        blueprint = Blueprint('ksul-bootstrap', __name__, static_folder=f'static/{self.static_folder}',
                                    static_url_path=f'/ksul{app.static_url_path}',
                                    template_folder='templates')


        super().init_app(app=app)

        app.register_blueprint(blueprint)