Bump min python from 3.7 to 3.12 (#6809)

* Bump min python from 3.7 to 3.12
* Remove typing-extensions
* Tidy
* Address Mypy errors
* GH Actions: use new bash-docker image
* Remove `types-six` dependency

Author: MetRonnie

.github/workflows/bash.yml

@@ -51,20 +51,21 @@ jobs:
           - '4.2'
           # if you use a value like 5.0, YAML will round it to 5, which will cause an error later on
           - '5.0'
+    env:
+      IMAGE: 'ghcr.io/cylc/cylc-bash-testing-2:master'
     steps:
       - name: Checkout
         uses: actions/checkout@v5
 
       - name: Run Docker container
         run: |
-          docker pull ghcr.io/cylc/cylc-bash-testing:master
-          docker run --name bash -v $(pwd -P):/root/cylc-flow --rm -t -d -m 1G --memory-swap 1G ghcr.io/cylc/cylc-bash-testing:master /bin/bash
+          docker pull "$IMAGE"
+          docker run --name bash -v $(pwd -P):/root/cylc-flow --rm -t -d -m 1G --memory-swap 1G "$IMAGE" /bin/bash
           docker ps -a
 
       - name: Install Cylc dependencies in the container
         run: |
-          docker exec bash python3.7 -m pip install six==1.12
-          docker exec -w /root/cylc-flow bash python3.7 -m pip install .[all]
+          docker exec -w /root/cylc-flow bash python3.12 -m pip install .[all] --break-system-packages
 
       - name: Set the container bash version
         run: docker exec bash update-alternatives --set bash /bash/bash-${{ matrix.bash-version }}

.github/workflows/build.yml

@@ -33,10 +33,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ['ubuntu-latest', 'macos-latest']
-        python: ['3.7', '3.8', '3.9', '3.10', '3']
-        exclude:
-          - os: 'macos-latest'
-            python: '3.7'
+        python: ['3.12', '3']
     steps:
       - name: Checkout
         uses: actions/checkout@v5

.github/workflows/test_conda-build.yml

@@ -28,7 +28,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.8', '3']
+        python-version: ['3.12', '3']
     env:
       ENV_FILE: conda-environment.yml
     steps:

.github/workflows/test_fast.yml

@@ -27,13 +27,13 @@ jobs:
       fail-fast: false # don't stop on first failure
       matrix:
         os: ['ubuntu-latest']
-        python-version: ['3.7', '3.8', '3.10', '3.11', '3.12', '3']
+        python-version: ['3.12', '3']
         include:
           - os: 'macos-latest'
-            python-version: '3.8'  # oldest version with arm64 builds
+            python-version: '3.12' # oldest version we support
           # non-utc timezone test
           - os: 'ubuntu-latest'
-            python-version: '3.9'  # not the oldest, not the most recent version
+            python-version: '3'
             time-zone: 'XXX-09:35'
     env:
       TZ: ${{ matrix.time-zone }}

.github/workflows/test_functional.yml

@@ -49,7 +49,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ['ubuntu-22.04']
-        python-version: ['3.7']
+        python-version: ['3.12'] # oldest version we support
         test-base: ['tests/f']
         chunk: ['1/4', '2/4', '3/4', '4/4']
         platform: ['_local_background* _local_at*']
@@ -65,27 +65,27 @@ jobs:
           # tests/k
           - name: 'flaky'
             os: 'ubuntu-latest'
-            python-version: '3.7'
+            python-version: '3.12'
             test-base: 'tests/k'
             chunk: '1/1'
             platform: '_local_background* _local_at*'
           # remote platforms
           - name: '_remote_background_indep_poll'
             os: 'ubuntu-latest'
-            python-version: '3.7'
+            python-version: '3.12'
             test-base: 'tests/f tests/k'
             chunk: '1/1'
             platform: '_remote_background_indep_poll _remote_at_indep_poll'
           - name: '_remote_background_indep_tcp'
             os: 'ubuntu-latest'
             test-base: 'tests/f tests/k'
-            python-version: '3.7'
+            python-version: '3.12'
             chunk: '1/1'
             platform: '_remote_background_indep_tcp _remote_at_indep_tcp'
           # macos
           - name: 'macos 1/5'
             os: 'macos-latest'
-            python-version: '3.8'  # oldest available
+            python-version: '3.12'  # oldest version we support
             test-base: 'tests/f'
             chunk: '1/5'
             platform: '_local_background*'

.github/workflows/test_tutorial_workflow.yml

@@ -34,7 +34,7 @@ jobs:
           - os: 'ubuntu-latest'
             python-version: '3'
           - os: 'ubuntu-22.04'
-            python-version: '3.7'
+            python-version: '3.12'
     runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     steps:

changes.d/6809.break.md

@@ -0,0 +1 @@
+Dropped support for Python 3.7-3.11. The minimum supported version is now 3.12.

conda-environment.yml

@@ -3,7 +3,6 @@ channels:
   - conda-forge
 dependencies:
   - ansimarkup >=1.0.0
-  - async-timeout>=3.0.0 # [py<3.11]
   - colorama >=0.4,<1.0
   - graphql-core >=3.2,<3.3
   - graphene >=3.4.0,<3.5
@@ -17,9 +16,7 @@ dependencies:
   - psutil >=5.6.0
   - python
   - pyzmq >=22
-  - importlib_metadata >=5.0 # [py<3.12]
   - urwid >=2.2,<3,!=2.6.2,!=2.6.3
-  - tomli >=2 # [py<3.11]
 
 # optional dependencies
   #- pandas >=1.0,<2

cylc/flow/__init__.py

@@ -58,17 +58,7 @@ def environ_init():
 
 def iter_entry_points(entry_point_name):
     """Iterate over Cylc entry points."""
-    import sys
-    if sys.version_info[:2] > (3, 11):
-        from importlib.metadata import entry_points
-    else:
-        # BACK COMPAT: importlib_metadata
-        #   importlib.metadata was added in Python 3.8. The required interfaces
-        #   were completed by 3.12. For lower versions we must use the
-        #   importlib_metadata backport.
-        # FROM: Python 3.7
-        # TO: Python: 3.12
-        from importlib_metadata import entry_points
+    from importlib.metadata import entry_points
     yield from (
         entry_point
         # for entry_point in entry_points()[entry_point_name]

cylc/flow/config.py

@@ -2363,21 +2363,18 @@ def load_graph(self):
     def check_terminal_outputs(self, terminals: Iterable[str]) -> None:
         """Check that task outputs have been registered with tasks.
 
-
         Where a "terminal output" is an output for a task at the end of a
         graph string, such as "end" in `start => middle => end`.
 
         Raises: WorkflowConfigError if a custom output is not defined.
         """
-        # BACK COMPAT: (On drop 3.7): Can be simplified with walrus :=
-        # if (b := a[1].strip("?")) not in TASK_QUALIFIERS
-        terminal_outputs = [
-            (a[0].strip("!"), a[1].strip("?"))
-            for a in (t.split(':') for t in terminals if ":" in t)
-            if (a[1].strip("?")) not in TASK_QUALIFIERS
-        ]
-
-        for task, output in terminal_outputs:
+        for t in terminals:
+            if ':' not in t:
+                continue
+            task, output = t.split(':')
+            if (output := output.strip('?')) in TASK_QUALIFIERS:
+                continue
+            task = task.strip('!')
             if output not in self.cfg['runtime'][task]['outputs']:
                 raise WorkflowConfigError(
                     f"Undefined custom output: {task}:{output}"