Static type checking

.github/workflows/python-app.yml

@@ -30,6 +30,8 @@ jobs:
         run: pip-audit -r requirements.txt
       - name: Check code for potential security vulnerabilities
         run: bandit -r . -x /tests
+      - name: Static type checking
+        run: mypy . --install-types --non-interactive 
       - name: Check code formatting
         run: |
           black . -t py312 -l 120 --check

.python-version

@@ -1 +1 @@
-3.12
+3.13

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.12-slim
+FROM python:3.13-slim
 
 RUN useradd appuser
 

app/__init__.py

@@ -1,9 +1,11 @@
+from typing import Type
+
 from flask import Flask
-from flask_assets import Bundle, Environment
+from flask_assets import Bundle, Environment  # type: ignore
 from flask_limiter import Limiter
 from flask_limiter.util import get_remote_address
-from flask_wtf.csrf import CSRFProtect
-from govuk_frontend_wtf.main import WTFormsHelpers
+from flask_wtf.csrf import CSRFProtect  # type: ignore
+from govuk_frontend_wtf.main import WTFormsHelpers  # type: ignore
 from jinja2 import ChoiceLoader, PackageLoader, PrefixLoader
 from werkzeug.middleware.proxy_fix import ProxyFix
 
@@ -17,7 +19,7 @@
 )
 
 
-def create_app(config_class=Config):
+def create_app(config_class: Type[Config] = Config) -> Flask:
     app = Flask(__name__, static_url_path="/assets")
     app.config.from_object(config_class)
     app.jinja_env.lstrip_blocks = True

app/demos/custom_validators.py

@@ -1,4 +1,4 @@
-from wtforms.validators import InputRequired
+from wtforms.validators import InputRequired  # type: ignore
 
 
 class RequiredIf(InputRequired):
@@ -14,7 +14,7 @@ def __init__(
 
         super(RequiredIf, self).__init__(*args, **kwargs)
 
-    def __call__(self, form, field):
+    def __call__(self, form, field) -> None:
         other_field = form._fields.get(self.other_field_name)
 
         if other_field is None:

app/demos/forms.py

@@ -1,5 +1,5 @@
-from flask_wtf import FlaskForm
-from govuk_frontend_wtf.wtforms_widgets import (
+from flask_wtf import FlaskForm  # type: ignore
+from govuk_frontend_wtf.wtforms_widgets import (  # type: ignore
     GovCharacterCount,
     GovCheckboxesInput,
     GovCheckboxInput,
@@ -12,7 +12,7 @@
     GovTextArea,
     GovTextInput,
 )
-from wtforms.fields import (
+from wtforms.fields import (  # type: ignore
     BooleanField,
     DateField,
     DateTimeField,
@@ -29,7 +29,7 @@
     SubmitField,
     TextAreaField,
 )
-from wtforms.validators import Email, EqualTo, InputRequired, Length, Optional, Regexp, ValidationError
+from wtforms.validators import Email, EqualTo, InputRequired, Length, Optional, Regexp, ValidationError  # type: ignore
 
 from app.demos.custom_validators import RequiredIf
 

app/demos/routes.py

@@ -1,7 +1,9 @@
 import os
+from typing import Union
 
 import yaml
 from flask import flash, redirect, render_template, url_for
+from werkzeug import Response
 from werkzeug.exceptions import NotFound
 
 from app.demos import bp
@@ -17,7 +19,7 @@ def components():
 
 
 @bp.route("/components/<string:component>", methods=["GET"])
-def component(component):
+def component(component: str) -> str:
     try:
         with open(f"app/demos/govuk_components/{component}/{component}.yaml") as yaml_file:
             fixtures = yaml.safe_load(yaml_file)
@@ -32,12 +34,12 @@ def component(component):
 
 
 @bp.route("/forms", methods=["GET"])
-def forms():
+def forms() -> str:
     return render_template("forms.html")
 
 
 @bp.route("/forms/bank-details", methods=["GET", "POST"])
-def bank_details():
+def bank_details() -> Union[str, Response]:
     form = BankDetailsForm()
     if form.validate_on_submit():
         flash("Demo form successfully submitted", "success")
@@ -46,7 +48,7 @@ def bank_details():
 
 
 @bp.route("/forms/create-account", methods=["GET", "POST"])
-def create_account():
+def create_account() -> Union[str, Response]:
     form = CreateAccountForm()
     if form.validate_on_submit():
         flash("Demo form successfully submitted", "success")
@@ -55,7 +57,7 @@ def create_account():
 
 
 @bp.route("/forms/kitchen-sink", methods=["GET", "POST"])
-def kitchen_sink():
+def kitchen_sink() -> Union[str, Response]:
     form = KitchenSinkForm()
     if form.validate_on_submit():
         flash("Demo form successfully submitted", "success")
@@ -64,7 +66,7 @@ def kitchen_sink():
 
 
 @bp.route("/forms/conditional-reveal", methods=["GET", "POST"])
-def conditional_reveal():
+def conditional_reveal() -> Union[str, Response]:
     form = ConditionalRevealForm()
     if form.validate_on_submit():
         flash("Demo form successfully submitted", "success")

app/main/forms.py

@@ -1,7 +1,7 @@
-from flask_wtf import FlaskForm
-from govuk_frontend_wtf.wtforms_widgets import GovRadioInput, GovSubmitInput
-from wtforms.fields import RadioField, SubmitField
-from wtforms.validators import InputRequired
+from flask_wtf import FlaskForm  # type: ignore
+from govuk_frontend_wtf.wtforms_widgets import GovRadioInput, GovSubmitInput  # type: ignore
+from wtforms.fields import RadioField, SubmitField  # type: ignore
+from wtforms.validators import InputRequired  # type: ignore
 
 
 class CookiesForm(FlaskForm):

app/main/routes.py

@@ -1,31 +1,34 @@
+from typing import Optional, Tuple, Union
+
 from flask import flash, json, make_response, redirect, render_template, request
-from flask_wtf.csrf import CSRFError
+from flask_wtf.csrf import CSRFError  # type: ignore
+from werkzeug import Response
 from werkzeug.exceptions import HTTPException
 
 from app.main import bp
 from app.main.forms import CookiesForm
 
 
 @bp.route("/", methods=["GET"])
-def index():
+def index() -> str:
     return render_template("index.html")
 
 
 @bp.route("/accessibility", methods=["GET"])
-def accessibility():
+def accessibility() -> str:
     return render_template("accessibility.html")
 
 
 @bp.route("/cookies", methods=["GET", "POST"])
-def cookies():
+def cookies() -> Union[str, Response]:
     form = CookiesForm()
     # Default cookies policy to reject all categories of cookie
     cookies_policy = {"functional": "no", "analytics": "no"}
 
     if form.validate_on_submit():
         # Update cookies policy consent from form data
-        cookies_policy["functional"] = form.functional.data
-        cookies_policy["analytics"] = form.analytics.data
+        cookies_policy["functional"] = str(form.functional.data)
+        cookies_policy["analytics"] = str(form.analytics.data)
 
         # Create flash message confirmation before rendering template
         flash("You’ve set your cookie preferences.", "success")
@@ -44,7 +47,7 @@ def cookies():
     elif request.method == "GET":
         if request.cookies.get("cookies_policy"):
             # Set cookie consent radios to current consent
-            cookies_policy = json.loads(request.cookies.get("cookies_policy"))
+            cookies_policy = json.loads(str(request.cookies.get("cookies_policy")))
             form.functional.data = cookies_policy["functional"]
             form.analytics.data = cookies_policy["analytics"]
         else:
@@ -55,16 +58,16 @@ def cookies():
 
 
 @bp.route("/privacy", methods=["GET"])
-def privacy():
+def privacy() -> str:
     return render_template("privacy.html")
 
 
 @bp.app_errorhandler(HTTPException)
-def http_exception(error):
+def http_exception(error: HTTPException) -> Tuple[str, Optional[int]]:
     return render_template(f"{error.code}.html"), error.code
 
 
 @bp.app_errorhandler(CSRFError)
-def csrf_error(error):
+def csrf_error(error: CSRFError) -> Response:
     flash("The form you were submitting has expired. Please try again.")
     return redirect(request.full_path)

requirements.txt

@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.12
+# This file is autogenerated by pip-compile with Python 3.13
 # by the following command:
 #
 #    pip-compile requirements.in
@@ -29,7 +29,7 @@ flask-assets==2.1.0
     # via -r requirements.in
 flask-limiter[redis]==3.8.0
     # via -r requirements.in
-flask-wtf==1.2.1
+flask-wtf==1.2.2
     # via govuk-frontend-wtf
 govuk-frontend-jinja==3.4.0
     # via
@@ -58,7 +58,7 @@ limits[redis]==3.13.0
     # via flask-limiter
 markdown-it-py==3.0.0
     # via rich
-markupsafe==3.0.1
+markupsafe==3.0.2
     # via
     #   jinja2
     #   werkzeug
@@ -75,21 +75,21 @@ pygments==2.18.0
     # via rich
 pyyaml==6.0.2
     # via -r requirements.in
-redis==5.1.1
+redis==5.2.0
     # via limits
-rich==13.9.2
+rich==13.9.4
     # via flask-limiter
 typing-extensions==4.12.2
     # via
     #   flask-limiter
     #   limits
 webassets==2.0
     # via flask-assets
-werkzeug==3.0.4
+werkzeug==3.1.1
     # via flask
 wrapt==1.16.0
     # via deprecated
-wtforms==3.1.2
+wtforms==3.2.1
     # via
     #   flask-wtf
     #   govuk-frontend-wtf