Flask example

This example shows how to use Dependency Injector with Flask.

The example application helps to search for repositories on the Github.

The source code is available on the Github.

Flask tutorial demonstrates how to build this application step-by-step.

Application structure

Application has next structure:

./
├── githubnavigator/
│   ├── templates
│   │   ├── base.html
│   │   └── index.py
│   ├── __init__.py
│   ├── application.py
│   ├── containers.py
│   ├── services.py
│   ├── tests.py
│   └── views.py
├── config.yml
└── requirements.txt

Container

Declarative container is defined in githubnavigator/containers.py:

"""Containers module."""

from dependency_injector import containers, providers
from github import Github

from . import services


class Container(containers.DeclarativeContainer):

    wiring_config = containers.WiringConfiguration(modules=[".views"])

    config = providers.Configuration(yaml_files=["config.yml"])

    github_client = providers.Factory(
        Github,
        login_or_token=config.github.auth_token,
        timeout=config.github.request_timeout,
    )

    search_service = providers.Factory(
        services.SearchService,
        github_client=github_client,
    )

Views

View has dependencies on search service and some config options. The dependencies are injected using Wiring feature.

Listing of githubnavigator/views.py:

"""Views module."""

from flask import request, render_template
from dependency_injector.wiring import inject, Provide

from .services import SearchService
from .containers import Container


@inject
def index(
        search_service: SearchService = Provide[Container.search_service],
        default_query: str = Provide[Container.config.default.query],
        default_limit: int = Provide[Container.config.default.limit.as_int()],
):
    query = request.args.get("query", default_query)
    limit = request.args.get("limit", default_limit, int)

    repositories = search_service.search_repositories(query, limit)

    return render_template(
        "index.html",
        query=query,
        limit=limit,
        repositories=repositories,
    )

Application factory

Application factory creates container, wires it with the views module, creates Flask app and setup routes.

Listing of githubnavigator/application.py:

"""Application module."""

from flask import Flask
from flask_bootstrap import Bootstrap

from .containers import Container
from . import views


def create_app() -> Flask:
    container = Container()
    container.config.github.auth_token.from_env("GITHUB_TOKEN")

    app = Flask(__name__)
    app.container = container
    app.add_url_rule("/", "index", views.index)

    bootstrap = Bootstrap()
    bootstrap.init_app(app)

    return app

Tests

Tests use Provider overriding feature to replace github client with a mock githubnavigator/tests.py:

"""Tests module."""

from unittest import mock

import pytest
from github import Github
from flask import url_for

from .application import create_app


@pytest.fixture
def app():
    app = create_app()
    yield app
    app.container.unwire()


def test_index(client, app):
    github_client_mock = mock.Mock(spec=Github)
    github_client_mock.search_repositories.return_value = [
        mock.Mock(
            html_url="repo1-url",
            name="repo1-name",
            owner=mock.Mock(
                login="owner1-login",
                html_url="owner1-url",
                avatar_url="owner1-avatar-url",
            ),
            get_commits=mock.Mock(return_value=[mock.Mock()]),
        ),
        mock.Mock(
            html_url="repo2-url",
            name="repo2-name",
            owner=mock.Mock(
                login="owner2-login",
                html_url="owner2-url",
                avatar_url="owner2-avatar-url",
            ),
            get_commits=mock.Mock(return_value=[mock.Mock()]),
        ),
    ]

    with app.container.github_client.override(github_client_mock):
        response = client.get(url_for("index"))

    assert response.status_code == 200
    assert b"Results found: 2" in response.data

    assert b"repo1-url" in response.data
    assert b"repo1-name" in response.data
    assert b"owner1-login" in response.data
    assert b"owner1-url" in response.data
    assert b"owner1-avatar-url" in response.data

    assert b"repo2-url" in response.data
    assert b"repo2-name" in response.data
    assert b"owner2-login" in response.data
    assert b"owner2-url" in response.data
    assert b"owner2-avatar-url" in response.data


def test_index_no_results(client, app):
    github_client_mock = mock.Mock(spec=Github)
    github_client_mock.search_repositories.return_value = []

    with app.container.github_client.override(github_client_mock):
        response = client.get(url_for("index"))

    assert response.status_code == 200
    assert b"Results found: 0" in response.data

Sources

Explore the sources on the Github.

Sponsor the project on GitHub: