Add MyPy coverage and enable type checking in CI

.github/workflows/main.yml

@@ -46,8 +46,8 @@ jobs:
       - name: Run tests
         run: uv run python -m pytest tests --cov --cov-config=pyproject.toml --cov-report=xml
 
-      # - name: Check typing
-      #   run: uv run mypy .
+      - name: Check typing
+        run: uv run mypy .
 
       - name: Upload coverage reports to Codecov with GitHub Action on Python 3.11
         uses: codecov/codecov-action@v4

Makefile

@@ -10,8 +10,8 @@ check: ## Run code quality tools.
 	@uv lock --locked
 	@echo "🚀 Linting code: Running pre-commit"
 	# @uv run pre-commit run -a
-	# @echo "🚀 Static type checking: Running mypy"
-	# @uv run mypy .
+	@echo "🚀 Static type checking: Running mypy"
+	@uv run mypy .
 	@echo "🚀 Checking for obsolete dependencies: Running deptry"
 	@uv run deptry .
 

examples/app_based_example.py

@@ -14,8 +14,9 @@
 except ImportError:
     # Path hack allows examples to be run without installation.
     import os
+    import sys
     parentdir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-    os.sys.path.insert(0, parentdir)
+    sys.path.insert(0, parentdir)
 
     from flask_cors import CORS
 

examples/blueprints_based_example.py

@@ -14,8 +14,9 @@
 except ImportError:
     # Path hack allows examples to be run without installation.
     import os
+    import sys
     parentdir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-    os.sys.path.insert(0, parentdir)
+    sys.path.insert(0, parentdir)
 
     from flask_cors import CORS
 

examples/view_based_example.py

@@ -15,8 +15,9 @@
 except ImportError:
     # Path hack allows examples to be run without installation.
     import os
+    import sys
     parentdir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-    os.sys.path.insert(0, parentdir)
+    sys.path.insert(0, parentdir)
 
     from flask_cors import cross_origin
 

flask_cors/core.py

@@ -177,15 +177,16 @@ def get_allow_headers(options, acl_request_headers):
 
 def get_cors_headers(options, request_headers, request_method):
     origins_to_set = get_cors_origins(options, request_headers.get("Origin"))
-    headers = MultiDict()
+    headers: MultiDict = MultiDict()
 
     if not origins_to_set:  # CORS is not enabled for this route
         return headers
 
     for origin in origins_to_set:
         headers.add(ACL_ORIGIN, origin)
 
-    headers[ACL_EXPOSE_HEADERS] = options.get("expose_headers")
+    if options.get("expose_headers"):
+        headers[ACL_EXPOSE_HEADERS] = options.get("expose_headers")
 
     if options.get("supports_credentials"):
         headers[ACL_CREDENTIALS] = "true"  # case sensitive

pyproject.toml

@@ -110,3 +110,9 @@ skip_empty = true
 [tool.coverage.run]
 branch = true
 source = ["flask_cors"]
+
+[tool.mypy]
+# Global options:
+warn_unused_configs = true
+ignore_missing_imports = true
+check_untyped_defs = true

tests/base_test.py

@@ -16,6 +16,8 @@
 
 
 class FlaskCorsTestCase(unittest.TestCase):
+    app: Flask
+
     def shortDescription(self):
         """
         Get's the one liner description to be displayed.

tests/core/test_override_headers.py

@@ -6,6 +6,7 @@
     Flask-Cors tests module
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask, Response
 

tests/decorator/test_allow_headers.py

@@ -6,6 +6,7 @@
     Flask-Cors tests module
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_credentials.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_duplicate_headers.py

@@ -6,6 +6,7 @@
     Flask-Cors tests module
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask, Response
 

tests/decorator/test_expose_headers.py

@@ -6,6 +6,7 @@
     Flask-Cors tests module
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_max_age.py

@@ -8,6 +8,7 @@
     :copyright: (c) 2016 by Cory Dolphin.
     :license: MIT, see LICENSE for more details.
 """
+import unittest
 from datetime import timedelta
 from ..base_test import FlaskCorsTestCase
 from flask import Flask

tests/decorator/test_methods.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_options.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_origins.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 import re

tests/decorator/test_private_network_headers.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 

tests/decorator/test_vary_header.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask, Response
 

tests/decorator/test_w3.py

@@ -9,6 +9,7 @@
     :license: MIT, see LICENSE for more details.
 """
 
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask
 from flask_cors import *

tests/extension/test_app_extension.py

@@ -10,6 +10,7 @@
 """
 
 import re
+import unittest
 from ..base_test import FlaskCorsTestCase
 from flask import Flask, jsonify