[SOLVED] Flask: how to automate OpenAPI v3 documentation?

I need to document an API written in pure Flask 2 and I'm looking for what is a consolidated approach for doing this. I found different viable solutions but being new to Python and Flask I'm not able to choose among them. The solutions I found are:

In order to separate the different API endpoints I use the Flask blueprint. The structure of a MWE is as follows:

I first defined two simple domain objects, Author and Book.

# author.py
class Author:
    def __init__(self, id: str, name: str):
        self.id = id
        self.name = name

# book.py
class Book:
    def __init__(self, id: str, name: str):
        self.id = id
        self.name = name

Next, I created a simple GET endpoint for both of them using two separate blueprints.

# author_apy.py
import json

from flask import Blueprint, Response

from domain.author import Author

author = Blueprint("author", __name__, url_prefix="/authors")


@author.get("/")
def authors():
    authors: list[Author] = []

    for i in range(10):
        author: Author = Author(str(i), "Author " + str(i))
        authors.append(author)

    authors_dicts = [author.__dict__ for author in authors]
    return Response(json.dumps(authors_dicts), mimetype="application/json")

and

# book_api.json
import json

from flask import Blueprint, Response

from domain.book import Book

book = Blueprint("book", __name__, url_prefix="/books")


@book.get("/")
def books():
    books: list[Book] = []

    for i in range(10):
        book: Book = Book(str(i), "Book " + str(i))
        books.append(book)

    books_dicts = [book.__dict__ for book in books]
    return Response(json.dumps(books_dicts), mimetype="application/json")

In the end I simply registered both the blueprints under the Flask app.

# app.py
from flask import Flask
from api.author.author_api import author
from api.book.book_api import book

app = Flask(__name__)
app.register_blueprint(author, url_prefix="/authors")
app.register_blueprint(book, url_prefix="/books")


@app.get('/')
def hello_world():
    return 'Flask - OpenAPI'


if __name__ == '__main__':
    app.run()

The whole source code is also available on GitHub.

Considering this minimal working example, I'd like to know what is the quickest way to automate the generation of an OpenAPI v3 yaml/JSON file, e.g. exposed on a /api-doc.yaml endpoint.

PS: this is my first API using Python and Flask. I am trying to reproduce what I'm able to do with Spring-Boot and SpringDoc

I encourage you to switch your project to FastAPI, it isn't much different or more difficult than Flask.

FastAPI docs about generating OpenAPI schema

It will not only allow you to generate OpenAPI docs / specification easily. It is also asynchronous, much faster and modern.

See also FastAPI Alternatives, Inspiration and Comparisons to read about differences.

Especially this citation from link above should explain why doing what you try to do may not be the best idea:

Flask REST frameworks

There are several Flask REST frameworks, but after investing the time and work into investigating them, I found that many are discontinued or abandoned, with several standing issues that made them unfit.