chore: constrain deps to maintain py 3.8 support

h4l · h4l · commit ed68011ba01c · 2025-05-23T11:59:05.000Z
Python 3.8 is unsupported and dependencies (such as pydantic) are now
shipping releases that fail to type check with mypy running in 3.8
compatibility mode. We run mypy in py 3.8 compatibility mode, so the
mypy tox environments must only use deps that support 3.8. And unit
tests run by py 3.8 must only use deps that support 3.8.

To constrain the deps for 3.8 support, we use two constraint files, one
for general environments that only constrains the dependencies that
python 3.8 interpreters use, and another for mypy that constraints the
dependencies that all interpreters use.

Signed-off-by: Hal Blackburn &lt;hwtb2@cam.ac.uk&gt;
diff --git a/requirements/constraints.txt b/requirements/constraints.txt
@@ -0,0 +1,10 @@
+# This is a requirements constraint file, see:
+# https://pip.pypa.io/en/stable/user_guide/#constraints-files
+
+# sanic stopped supporting 3.8 in 24.12:
+# https://sanic.dev/en/release-notes/changelog.html#version-24120-
+sanic<24.12.0 ; python_version == '3.8'
+
+# pydantic stopped supporting 3.8 in 2.11.0:
+# https://github.com/pydantic/pydantic/releases/tag/v2.11.0
+pydantic<2.11.0 ; python_version == '3.8'
diff --git a/requirements/mypy-constraints.txt b/requirements/mypy-constraints.txt
@@ -0,0 +1,9 @@
+# This is a requirements constraint file, see:
+# https://pip.pypa.io/en/stable/user_guide/#constraints-files
+
+# Because we run mypy in python 3.8 compatibility mode, dependencies must be
+# versions that support 3.8.
+
+# pydantic stopped supporting 3.8 in 2.11.0:
+# https://github.com/pydantic/pydantic/releases/tag/v2.11.0
+pydantic<2.11.0
diff --git a/requirements/test.txt b/requirements/test.txt
@@ -4,12 +4,7 @@ flake8-print
 pytest
 pytest-cov
 # web app tests
-
-# sanic stopped supporting 3.8 in 24.12:
-# https://sanic.dev/en/release-notes/changelog.html#version-24120-
-sanic         ; python_version >= '3.9'
-sanic<24.12.0 ; python_version <  '3.9'
-
+sanic
 sanic-testing
 aiohttp
 Pillow
diff --git a/tox.ini b/tox.ini
@@ -8,6 +8,7 @@ deps =
     -r{toxinidir}/requirements/test.txt
     -r{toxinidir}/requirements/publish.txt
 setenv =
+    PIP_CONSTRAINT={toxinidir}/requirements/constraints.txt
     PYTESTARGS = -v -s --tb=long --cov=cloudevents --cov-report term-missing --cov-fail-under=95
 commands = pytest {env:PYTESTARGS} {posargs}
 
@@ -33,6 +34,8 @@ commands =
 
 [testenv:mypy]
 basepython = python3.11
+setenv =
+    PIP_CONSTRAINT={toxinidir}/requirements/mypy-constraints.txt
 deps =
     -r{toxinidir}/requirements/mypy.txt
     # mypy needs test dependencies to check test modules
@@ -42,6 +45,7 @@ commands = mypy cloudevents
 [testenv:mypy-samples-{image,json}]
 basepython = python3.11
 setenv =
+    PIP_CONSTRAINT={toxinidir}/requirements/mypy-constraints.txt
     mypy-samples-image: SAMPLE_DIR={toxinidir}/samples/http-image-cloudevents
     mypy-samples-json: SAMPLE_DIR={toxinidir}/samples/http-json-cloudevents
 deps =
