From cd4cf2eebba87c2db4c608ad3db075656ba54f0e Mon Sep 17 00:00:00 2001
From: Chris Marchbanks <csmarchbanks@gmail.com>
Date: Wed, 1 Dec 2021 00:15:19 -0700
Subject: [PATCH] Add mypy linting to the CI pipeline

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>
---
 .circleci/config.yml          |  7 +++++++
 mypy.ini                      |  5 +++++
 tests/test_core.py            |  6 +-----
 tests/test_exposition.py      |  7 +------
 tests/test_graphite_bridge.py |  6 +-----
 tox.ini                       | 11 ++++++++++-
 6 files changed, 25 insertions(+), 17 deletions(-)
 create mode 100644 mypy.ini

diff --git a/.circleci/config.yml b/.circleci/config.yml
index ced00806..f3712da7 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -19,6 +19,12 @@ jobs:
       - checkout
       - run: pip install tox
       - run: tox -e isort
+  mypy_lint:
+    executor: python
+    steps:
+      - checkout
+      - run: pip install tox
+      - run: tox -e mypy
   test:
     parameters:
       python:
@@ -64,6 +70,7 @@ workflows:
     jobs:
       - flake8_lint
       - isort_lint
+      - mypy_lint
       - test:
           matrix:
             parameters:
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 00000000..c1b51f59
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,5 @@
+[mypy]
+exclude = prometheus_client/decorator.py|prometheus_client/twisted|tests/test_twisted.py
+
+[mypy-prometheus_client.decorator]
+follow_imports = skip
diff --git a/tests/test_core.py b/tests/test_core.py
index 38bc20c4..36d521cc 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1,5 +1,6 @@
 from concurrent.futures import ThreadPoolExecutor
 import time
+import unittest
 
 import pytest
 
@@ -11,11 +12,6 @@
 )
 from prometheus_client.decorator import getargspec
 
-try:
-    import unittest2 as unittest
-except ImportError:
-    import unittest
-
 
 def assert_not_observable(fn, *args, **kwargs):
     """
diff --git a/tests/test_exposition.py b/tests/test_exposition.py
index a52805ea..fd130552 100644
--- a/tests/test_exposition.py
+++ b/tests/test_exposition.py
@@ -1,3 +1,4 @@
+from http.server import BaseHTTPRequestHandler, HTTPServer
 import threading
 import time
 import unittest
@@ -15,12 +16,6 @@
     passthrough_redirect_handler,
 )
 
-try:
-    from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
-except ImportError:
-    # Python 3
-    from http.server import BaseHTTPRequestHandler, HTTPServer
-
 
 class TestGenerateText(unittest.TestCase):
     def setUp(self):
diff --git a/tests/test_graphite_bridge.py b/tests/test_graphite_bridge.py
index 73b38204..5e281486 100644
--- a/tests/test_graphite_bridge.py
+++ b/tests/test_graphite_bridge.py
@@ -1,14 +1,10 @@
+import socketserver as SocketServer
 import threading
 import unittest
 
 from prometheus_client import CollectorRegistry, Gauge
 from prometheus_client.bridge.graphite import GraphiteBridge
 
-try:
-    import SocketServer
-except ImportError:
-    import socketserver as SocketServer
-
 
 def fake_timer():
     return 1434898897.5
diff --git a/tox.ini b/tox.ini
index 8a93a160..25a7a00a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = coverage-clean,py3.6,py3.7,py3.8,py3.9,py3.10,pypy3.7,py3.9-nooptionals,coverage-report,flake8,isort
+envlist = coverage-clean,py3.6,py3.7,py3.8,py3.9,py3.10,pypy3.7,py3.9-nooptionals,coverage-report,flake8,isort,mypy
 
 
 [base]
@@ -48,6 +48,15 @@ skip_install = true
 commands =
     isort --check prometheus_client/ tests/ setup.py
 
+[testenv:mypy]
+deps =
+    pytest
+    asgiref
+    mypy==0.910
+skip_install = true
+commands =
+    mypy --install-types --non-interactive prometheus_client/ tests/
+
 [flake8]
 ignore =
     D,