👌 IMPROVE: Support old entry points interface (#321)

Despite pinning to `importlib-metdata>=3.6` in #319,
python/importlib_metadata#308
could still cause Conda installs to fail using the newer interface.
So now the pinning is removed, and the new interface is only used if available.

README.md

@@ -4,6 +4,7 @@
 [![Coverage Status][codecov-badge]][codecov-link]
 [![Documentation Status][rtd-badge]][rtd-link]
 [![PyPI][pypi-badge]][pypi-link]
+[![Conda Version][conda-badge]][conda-link]
 
 A collection of tools for working with Jupyter Notebooks in Sphinx.
 
@@ -26,3 +27,5 @@ See the [Contributing Guide](https://myst-nb.readthedocs.io/en/latest/develop/co
 [codecov-link]: https://codecov.io/gh/executablebooks/MyST-NB
 [pypi-badge]: https://img.shields.io/pypi/v/myst-nb.svg
 [pypi-link]: https://pypi.org/project/myst-nb
+[conda-badge]: https://img.shields.io/conda/vn/conda-forge/myst-nb.svg
+[conda-link]: https://anaconda.org/conda-forge/myst-nb

myst_nb/render_outputs.py

@@ -67,12 +67,19 @@ class MystNbEntryPointError(SphinxError):
     category = "MyST NB Renderer Load"
 
 
-def load_renderer(name) -> "CellOutputRendererBase":
+def load_renderer(name: str) -> "CellOutputRendererBase":
     """Load a renderer,
     given a name within the ``myst_nb.mime_render`` entry point group
     """
-    eps = entry_points(group="myst_nb.mime_render", name=name)
-    if name in eps.names:
+    all_eps = entry_points()
+    if hasattr(all_eps, "select"):
+        # importlib_metadata >= 3.6 or importlib.metadata in python >=3.10
+        eps = all_eps.select(group="myst_nb.mime_render", name=name)
+        found = name in eps.names
+    else:
+        eps = {ep.name: ep for ep in all_eps.get("myst_nb.mime_render", [])}
+        found = name in eps
+    if found:
         klass = eps[name].load()
         if not issubclass(klass, CellOutputRendererBase):
             raise MystNbEntryPointError(

setup.cfg

@@ -39,7 +39,7 @@ project_urls =
 packages = find:
 install_requires =
     docutils>=0.15
-    importlib_metadata>=3.6
+    importlib_metadata
     ipython
     ipywidgets>=7.0.0,<8
     jupyter-cache~=0.4.1