CI: adding back sphinx9 testing

Author: bsipocz

.github/workflows/tests.yml

@@ -19,8 +19,8 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
-        sphinx: ["~=8.0"]  # temporary limit, bring it back to newest sphinx once we are sphinx9 compatible
+        python-version: ["3.11", "3.12", "3.13", "3.14"]
+        sphinx: [""]  # Newest Sphinx
         myst-parser: [""]  # Newest MyST Parser (any)
         include:
           # Just check the other platforms once
@@ -53,9 +53,9 @@ jobs:
             pillow: "==11.0.0"
           # Newest known-compatible dependencies
           - os: ubuntu-latest
-            python-version: "3.13"
-            sphinx: "~=8.0"
-            myst-parser: "==4.0.0"
+            python-version: "3.14"
+            sphinx: "~=9.0"
+            myst-parser: "~=5.0"
             pillow: "==11.0.0"
 
     runs-on: ${{ matrix.os }}
@@ -79,7 +79,7 @@ jobs:
 
   publish:
 
-    name: Publish to PyPi
+    name: Publish to PyPI
     needs: [tests]
     if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
     runs-on: ubuntu-latest

pyproject.toml

@@ -43,7 +43,7 @@ dependencies = [
     "myst-parser>=1.0.0",
     "nbformat>=5.0",
     "pyyaml",
-    "sphinx>=5,<9",  # If we get bugs for older versions, just pin this higher
+    "sphinx>=5",  # If we get bugs for older versions, just pin this higher
     "typing-extensions",
     # ipykernel is not a requirement of the library,
     # but is a common requirement for users (registers the python3 kernel)
@@ -175,8 +175,8 @@ filterwarnings = [
     'ignore:datetime.datetime.utcnow\(\) is deprecated:DeprecationWarning:jupyter_cache',
     # From matplotlib’s dependencies
     'ignore::DeprecationWarning:pyparsing',  # imports deprecated `sre_constants`
-    # From myst-parser on Sphinx 9
-    'ignore:.*MystReferenceResolver.app.*:DeprecationWarning',
+    # From myst-parser on Sphinx 9 we hit RemovedInSphinx11Warning
+    'ignore:.*MystReferenceResolver.app.*',
     # Upstream myst-parser still hits env.app deprecations under Sphinx 9
     'ignore:.*env\\.app.*:DeprecationWarning:myst_parser',
     # Windows issues, some may need to be fixed in MyST-NB, others are upstream