From f5ea78ce9b40ccc4a316527b225c759587622705 Mon Sep 17 00:00:00 2001
From: Ronnie Dutta <61982285+MetRonnie@users.noreply.github.com>
Date: Fri, 5 Sep 2025 10:44:23 +0100
Subject: [PATCH] Bump minimum supported Python version to 3.12

---
 .github/workflows/build.yml     | 3 ++-
 .github/workflows/test.yml      | 4 ++--
 changes.d/729.break.md          | 1 +
 cylc/uiserver/jupyter_config.py | 9 +--------
 mypy.ini                        | 2 +-
 pyproject.toml                  | 4 ++--
 setup.cfg                       | 8 +-------
 7 files changed, 10 insertions(+), 21 deletions(-)
 create mode 100644 changes.d/729.break.md

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 6b4c930d..651ffd94 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,7 +32,7 @@ jobs:
     strategy:
       matrix:
         os: ['ubuntu-latest', 'macos-latest']
-        python: ['3.9', '3']  # oldest/newest supported versions
+        python: ['3.12', '3']  # oldest/newest supported versions
     steps:
       - name: Checkout
         uses: actions/checkout@v5
@@ -54,6 +54,7 @@ jobs:
       - name: Inspect
         run: |
           unzip -l dist/*.whl | tee files
+          set -x
           grep -E 'cylc_uiserver.*.dist-info/.*COPYING' files
           grep 'cylc/uiserver/py.typed' files
           grep 'cylc/uiserver/ui' files
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 10feff1f..da26c217 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -27,10 +27,10 @@ jobs:
       fail-fast: false
       matrix:
         os: ['ubuntu-latest']
-        python-version: ['3.9', '3']
+        python-version: ['3.12', '3']
         include:
           - os: 'macos-latest'
-            python-version: '3.9'  # oldest supported
+            python-version: '3.12'  # oldest supported
     env:
       PYTEST_ADDOPTS: --cov --color=yes
 
diff --git a/changes.d/729.break.md b/changes.d/729.break.md
new file mode 100644
index 00000000..81004927
--- /dev/null
+++ b/changes.d/729.break.md
@@ -0,0 +1 @@
+Minimum supported Python version is now 3.12.
diff --git a/cylc/uiserver/jupyter_config.py b/cylc/uiserver/jupyter_config.py
index 2db21343..afde2cb0 100644
--- a/cylc/uiserver/jupyter_config.py
+++ b/cylc/uiserver/jupyter_config.py
@@ -15,15 +15,8 @@
 
 # Configuration file for jupyterhub.
 
+from importlib.resources import files
 from pathlib import Path
-import sys
-
-
-if sys.version_info[:2] > (3, 8):
-    from importlib.resources import files
-else:
-    # BACK_COMPAT: importlib_resources
-    from importlib_resources import files
 
 from cylc.uiserver import (
     __file__ as uis_pkg,
diff --git a/mypy.ini b/mypy.ini
index 96059f54..75f3dff3 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -1,5 +1,5 @@
 [mypy]
-python_version = 3.9
+python_version = 3.12
 ignore_missing_imports = True
 files = cylc/uiserver
 # don't run mypy on these files directly
diff --git a/pyproject.toml b/pyproject.toml
index 3eaf2766..54e659b1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -63,7 +63,7 @@ verbosity_assertions = 2
 
 [tool.ruff]
 line-length = 79
-target-version = "py37"
+target-version = "py312"
 
 [tool.ruff.format]
 quote-style = "preserve"
@@ -71,7 +71,7 @@ quote-style = "preserve"
 
 [tool.black]
 line-length = 79
-target-version = ['py37']
+target-version = ['py312']
 skip-string-normalization = true
 
 
diff --git a/setup.cfg b/setup.cfg
index 755db55d..669ace2d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -33,17 +33,12 @@ classifiers =
     License :: OSI Approved :: GNU General Public License v3 (GPLv3)
     Operating System :: POSIX
     Programming Language :: Python
-    Programming Language :: Python :: 3.9
-    Programming Language :: Python :: 3.10
-    Programming Language :: Python :: 3.11
-    Programming Language :: Python :: 3.12
-    Programming Language :: Python :: 3.13
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython
 
 [options]
 packages = find_namespace:
-python_requires = >=3.9
+python_requires = >=3.12
 include_package_data = True
 install_requires =
     # NB: We have cylc-flow at the top to force it to install its transitive
@@ -52,7 +47,6 @@ install_requires =
     # bleeding-edge version.
     cylc-flow==8.6.*
     ansimarkup>=1.0.0
-    importlib-resources>=1.3.0; python_version < "3.9"
     jupyter_server>=2.13.0
     requests
     packaging