Add 3.12 to CI (#3863)

Adds Python 3.12 to CI.
Because `tree-sitter`/`tree-sitter-languages` can't be installed on 3.12 yet, we need to run slightly different commands when installing dependencies/running tests on 3.12.

See for more context: #3491 (comment)

.github/workflows/pythonpackage.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
     defaults:
       run:
         shell: bash
@@ -32,9 +32,18 @@ jobs:
           cache: 'poetry'
       - name: Install dependencies
         run: poetry install --no-interaction --extras syntax
+        if: ${{ matrix.python-version != '3.12' }}
+      - name: Install dependencies for 3.12  # https://github.com/Textualize/textual/issues/3491#issuecomment-1854156476
+        run: poetry install --no-interaction
+        if: ${{ matrix.python-version == '3.12' }}
       - name: Test with pytest
         run: |
           poetry run pytest tests -v --cov=./src/textual --cov-report=xml:./coverage.xml --cov-report term-missing
+        if: ${{ matrix.python-version != '3.12' }}
+      - name: Test with pytest for 3.12  # https://github.com/Textualize/textual/issues/3491#issuecomment-1854156476
+        run: |
+          poetry run pytest tests -v --cov=./src/textual --cov-report=xml:./coverage.xml --cov-report term-missing -m 'not syntax'
+        if: ${{ matrix.python-version == '3.12' }}
       - name: Upload snapshot report
         if: always()
         uses: actions/upload-artifact@v3

pyproject.toml

@@ -83,6 +83,7 @@ testpaths = ["tests"]
 addopts = "--strict-markers"
 markers = [
     "integration_test: marks tests as slow integration tests (deselect with '-m \"not integration_test\"')",
+    "syntax: marks tests that require syntax highlighting (deselect with '-m \"not syntax\"')",
 ]
 
 [build-system]

tests/snapshot_tests/test_snapshots.py

@@ -795,6 +795,7 @@ def test_nested_fr(snap_compare) -> None:
     assert snap_compare(SNAPSHOT_APPS_DIR / "nested_fr.py")
 
 
+@pytest.mark.syntax
 @pytest.mark.parametrize("language", BUILTIN_LANGUAGES)
 def test_text_area_language_rendering(language, snap_compare):
     # This test will fail if we're missing a snapshot test for a valid
@@ -846,6 +847,7 @@ def setup_selection(pilot):
     )
 
 
+@pytest.mark.syntax
 @pytest.mark.parametrize(
     "theme_name", [theme.name for theme in TextAreaTheme.builtin_themes()]
 )

tests/text_area/test_languages.py

@@ -1,5 +1,3 @@
-import sys
-
 import pytest
 
 from textual.app import App, ComposeResult
@@ -61,7 +59,7 @@ async def test_setting_unknown_language():
             text_area.language = "this-language-doesnt-exist"
 
 
-@pytest.mark.skipif(sys.version_info < (3, 8), reason="tree-sitter requires python3.8 or higher")
+@pytest.mark.syntax
 async def test_register_language():
     app = TextAreaApp()
 
@@ -84,7 +82,7 @@ async def test_register_language():
         assert text_area.language == "elm"
 
 
-@pytest.mark.skipif(sys.version_info < (3, 8), reason="tree-sitter requires python3.8 or higher")
+@pytest.mark.syntax
 async def test_register_language_existing_language():
     app = TextAreaApp()
     async with app.run_test():