Part of #3928 [Web Examples] Add First Class Python Support (#4107)

# Pull Request 
Adds First Class Python Support [Web Examples]
Part of #3928

## Description
Web Examples for Python `1-hello-flask`, `2-todo-flask`,
`3-hello-django`, `4-todo-django` Examples

## Related Issues
- Link to related issue #3928.

## Checklist

- [x]  1-hello-flask
- [x]  2-todo-flask
- [x]  3-hello-django
- [x]  4-todo-django
- [x] Updated Documentation

## Status
Require Review!!!

docs/modules/ROOT/nav.adoc

@@ -36,6 +36,7 @@
 *** xref:pythonlib/module-config.adoc[]
 *** xref:pythonlib/dependencies.adoc[]
 *** xref:pythonlib/publishing.adoc[]
+*** xref:pythonlib/web-examples.adoc[]
 * xref:comparisons/why-mill.adoc[]
 ** xref:comparisons/maven.adoc[]
 ** xref:comparisons/gradle.adoc[]

docs/modules/ROOT/pages/pythonlib/web-examples.adoc

@@ -0,0 +1,25 @@
+= Python Web Project Examples
+:page-aliases: Python_Web_Examples.adoc
+
+include::partial$gtag-config.adoc[]
+
+This page provides examples of using Mill as a build tool for Python web applications.
+It includes setting up a basic "Hello, World!" application and developing a fully
+functional https://todomvc.com/[TodoMVC] app with Flask and Django, showcasing best practices
+for project organization, scalability, and maintainability.
+
+== Flask Hello World App
+
+include::partial$example/pythonlib/web/1-hello-flask.adoc[]
+
+== Flask TodoMVC App
+
+include::partial$example/pythonlib/web/2-todo-flask.adoc[]
+
+== Django Hello World App
+
+include::partial$example/pythonlib/web/3-hello-django.adoc[]
+
+== Django TodoMVC App
+
+include::partial$example/pythonlib/web/4-todo-django.adoc[]

example/package.mill

@@ -70,6 +70,7 @@ object `package` extends RootModule with Module {
     object dependencies extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "dependencies"))
     object publishing extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "publishing"))
     object module extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "module"))
+    object web extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "web"))
   }
 
   object cli extends Module{

example/pythonlib/web/1-hello-flask/build.mill

@@ -0,0 +1,39 @@
+// This example uses Mill to manage a Flask app that serves `"Hello, Mill!"`
+// at the root URL (`/`), with Flask installed as a dependency
+// and tests enabled using `unittest`.
+package build
+import mill._, pythonlib._
+
+object foo extends PythonModule {
+
+  def mainScript = Task.Source { millSourcePath / "src/foo.py" }
+
+  def pythonDeps = Seq("flask==3.1.0")
+
+  object test extends PythonTests with TestModule.Unittest
+
+}
+
+//  Running these commands will test and run the Flask server with desired outputs.
+
+// The app is ready to serve at `http://localhost:5000`.
+
+/** Usage
+
+> ./mill foo.test
+...
+test_hello_flask (test.TestScript...)
+Test the '/' endpoint. ... ok
+...
+Ran 1 test...
+OK
+...
+
+> ./mill foo.runBackground
+
+> curl http://localhost:5000
+...<h1>Hello, Mill!</h1>...
+
+> ./mill clean foo.runBackground
+
+*/

example/pythonlib/web/1-hello-flask/foo/src/foo.py

@@ -0,0 +1,12 @@
+from flask import Flask
+
+app = Flask(__name__)
+
+
+@app.route("/")
+def hello_world():
+    return "<h1>Hello, Mill!</h1>"
+
+
+if __name__ == "__main__":
+    app.run(debug=True)

example/pythonlib/web/1-hello-flask/foo/test/src/test.py

@@ -0,0 +1,21 @@
+import unittest
+from foo import app  # type: ignore
+
+
+class TestScript(unittest.TestCase):
+    def setUp(self):
+        """Set up the test client before each test."""
+        self.app = app.test_client()  # Initialize the test client
+        self.app.testing = True  # Enable testing mode for better error handling
+
+    def test_hello_flask(self):
+        """Test the '/' endpoint."""
+        response = self.app.get("/")  # Simulate a GET request to the root endpoint
+        self.assertEqual(response.status_code, 200)  # Check the HTTP status code
+        self.assertIn(
+            b"Hello, Mill!", response.data
+        )  # Check if the response contains the expected text
+
+
+if __name__ == "__main__":
+    unittest.main()

example/pythonlib/web/2-todo-flask/build.mill

@@ -0,0 +1,64 @@
+// This is a `Flask`-based https://todomvc.com/[TodoMVC] application managed and built using `Mill`.
+// It allows users to `add`, `edit`, `delete`, and `view` tasks stored in a Python Data Structure.
+// Tasks can be filtered as `all`, `active`, or `completed` based on their state.
+// The application demonstrates dynamic rendering using Flask's routing and templating features.
+package build
+import mill._, pythonlib._
+
+object todo extends PythonModule {
+
+  def mainScript = Task.Source { millSourcePath / "src/app.py" }
+
+  def pythonDeps = Seq("flask==3.1.0", "Flask-SQLAlchemy==3.1.1", "Flask-WTF==1.2.2")
+
+  object test extends PythonTests with TestModule.Unittest
+  object itest extends PythonTests with TestModule.Unittest
+
+}
+
+// Apart from running a web server, this example demonstrates:
+
+// - **Serving HTML templates** using **Jinja2** (Flask's default templating engine).
+// - **Managing static files** such as JavaScript, CSS, and images.
+// - **Filtering and managing tasks** in-memory using Python data structures.
+// - **Unit testing** using **unittest** for testing task operations.
+// - **Integration testing** using **unittest** for end-to-end application behavior.
+
+// This example also utilizes **Mill** for managing `dependencies`, `builds`, and `tests`,
+// offering an efficient development workflow.
+
+// The app is ready to serve at `http://localhost:5001`.
+
+/** Usage
+
+> ./mill todo.test
+...
+test_add_todo (test.TestTodoApp...) ... ok
+test_delete_todo (test.TestTodoApp...) ... ok
+test_edit_todo (test.TestTodoApp...) ... ok
+test_filter_todos (test.TestTodoApp...) ... ok
+test_toggle_all (test.TestTodoApp...) ... ok
+test_toggle_todo (test.TestTodoApp...) ... ok
+...Ran 6 tests...
+OK
+...
+
+> ./mill todo.itest
+...
+test_add_and_list_todos (test.TestTodoAppIntegration...) ... ok
+test_delete_todo (test.TestTodoAppIntegration...) ... ok
+test_edit_and_list_todos (test.TestTodoAppIntegration...) ... ok
+test_toggle_all_todos (test.TestTodoAppIntegration...) ... ok
+test_toggle_and_list_todos (test.TestTodoAppIntegration...) ... ok
+...Ran 5 tests...
+OK
+...
+
+> ./mill todo.runBackground
+
+> curl http://localhost:5001
+...What needs to be done...
+
+> ./mill clean todo.runBackground
+
+*/

example/pythonlib/web/2-todo-flask/todo/itest/src/test.py

@@ -0,0 +1,68 @@
+import unittest
+from app import app, todos
+
+
+class TestTodoAppIntegration(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        # Set up the test client for the app
+        cls.client = app.test_client()
+
+    def setUp(self):
+        # Clear the todos list before each test
+        global todos
+        todos.clear()
+
+    def test_add_and_list_todos(self):
+        # Test adding a todo and listing all todos
+        response = self.client.post("/add/all", data="Test Todo")
+        self.assertEqual(response.status_code, 200)
+        # Fetch the todos list and verify the item was added
+        response = self.client.post("/list/all", data="")
+        self.assertIn(b"Test Todo", response.data)
+
+    def test_toggle_and_list_todos(self):
+        # Test adding a todo, toggling it, and listing active/completed todos
+        self.client.post("/add/all", data="Test Todo")
+        response = self.client.post("/toggle/all/0", data="")
+        # Check if the todo is toggled
+        self.assertEqual(response.status_code, 200)
+        # Now, test filtering todos based on active/completed state
+        response = self.client.post("/list/active", data="")
+        self.assertNotIn(b"Test Todo", response.data)
+        response = self.client.post("/list/completed", data="")
+        self.assertIn(b"Test Todo", response.data)
+
+    def test_edit_and_list_todos(self):
+        # Test adding a todo, editing it, and then verifying the updated text
+        self.client.post("/add/all", data="Test Todo")
+        response = self.client.post("/edit/all/0", data="Updated Todo")
+        # Check that the todo was updated
+        response = self.client.post("/list/all", data="")
+        self.assertIn(b"Updated Todo", response.data)
+        self.assertNotIn(b"Test Todo", response.data)
+
+    def test_delete_todo(self):
+        # Test adding and deleting a todo
+        self.client.post("/add/all", data="Test Todo")
+        response = self.client.post("/delete/all/0", data="")
+        # Verify that the todo was deleted
+        response = self.client.post("/list/all", data="")
+        self.assertNotIn(b"Test Todo", response.data)
+
+    def test_toggle_all_todos(self):
+        # Test toggling all todos
+        self.client.post("/add/all", data="Todo 1")
+        self.client.post("/add/all", data="Todo 2")
+        response = self.client.post("/toggle-all/all", data="")
+        response = self.client.post("/list/completed", data="")
+        self.assertIn(b"Todo 1", response.data)
+        self.assertIn(b"Todo 2", response.data)
+        response = self.client.post("/toggle-all/all", data="")
+        response = self.client.post("/list/active", data="")
+        self.assertIn(b"Todo 1", response.data)
+        self.assertIn(b"Todo 2", response.data)
+
+
+if __name__ == "__main__":
+    unittest.main()

example/pythonlib/web/2-todo-flask/todo/src/app.py

@@ -0,0 +1,96 @@
+from flask import Flask, render_template, request
+from dataclasses import dataclass
+from typing import List
+
+app = Flask(__name__, static_folder="../static", template_folder="../templates")
+
+
+@dataclass
+class Todo:
+    checked: bool
+    text: str
+
+
+todos: List[Todo] = []
+
+
+@app.route("/")
+def index():
+    return render_template("base.html", todos=todos, state="all")
+
+
+def render_body(state: str):
+    filtered_todos = {
+        "all": todos,
+        "active": [todo for todo in todos if not todo.checked],
+        "completed": [todo for todo in todos if todo.checked],
+    }[state]
+    return render_template("index.html", todos=filtered_todos, state=state)
+
+
+def filter_todos(state):
+    """Filter todos based on the state (all, active, completed)."""
+    if state == "all":
+        return todos
+    elif state == "active":
+        return [todo for todo in todos if not todo.checked]
+    elif state == "completed":
+        return [todo for todo in todos if todo.checked]
+
+
+@app.route("/edit/<state>/<int:index>", methods=["POST"])
+def edit_todo(state, index):
+    """Edit the text of a todo."""
+    global todos
+    updated_text = request.data.decode("utf-8")
+    # Update the text attribute of the Todo object
+    todos[index].text = updated_text
+    filtered_todos = filter_todos(state)
+    return render_template("index.html", todos=filtered_todos, state=state)
+
+
+@app.route("/list/<state>", methods=["POST"])
+def list_todos(state):
+    return render_body(state)
+
+
+@app.route("/add/<state>", methods=["POST"])
+def add_todo(state):
+    todos.insert(0, Todo(checked=False, text=request.data.decode("utf-8")))
+    return render_body(state)
+
+
+@app.route("/delete/<state>/<int:index>", methods=["POST"])
+def delete_todo(state, index):
+    if 0 <= index < len(todos):
+        todos.pop(index)
+    return render_body(state)
+
+
+@app.route("/toggle/<state>/<int:index>", methods=["POST"])
+def toggle(state, index):
+    if 0 <= index < len(todos):
+        todos[index].checked = not todos[index].checked
+    return render_body(state)
+
+
+@app.route("/clear-completed/<state>", methods=["POST"])
+def clear_completed(state):
+    global todos
+    todos = [todo for todo in todos if not todo.checked]
+    return render_body(state)
+
+
+@app.route("/toggle-all/<state>", methods=["POST"])
+def toggle_all(state):
+    global todos
+
+    all_checked = all(todo.checked for todo in todos)
+    for todo in todos:
+        todo.checked = not all_checked
+
+    return render_body(state)
+
+
+if __name__ == "__main__":
+    app.run(debug=True, port=5001)