Migrate from pkg_resources to importlib.metadata (#299)

CHANGELOG.rst

@@ -1,8 +1,14 @@
-2.4.3 (in development)
+2.5.0 (in development)
 ----------------------
 
 * Add support for the rinohtype builder (reported by brechtm, see issue #275).
 
+* Migrate from ``pkg_resources`` to ``importlib.metadata``. A side effect of
+  this migration is that
+  **plugins registered at runtime are longer exposed as entry points**.
+  This is because ``importlib`` does not allow runtime modification of
+  entry points.
+
 2.4.2 (10 April 2022)
 ---------------------
 

requirements.txt

@@ -3,3 +3,4 @@ docutils>=0.8
 pybtex>=0.24
 pybtex-docutils>=1.0.0
 dataclasses; python_version < '3.7'
+importlib_metadata>=3.6; python_version < '3.10'

src/sphinxcontrib/bibtex/plugin.py

@@ -1,30 +1,47 @@
-import pkg_resources
-from pybtex.plugin import _FakeEntryPoint
-from typing import Type, Any, Dict
+import sys
+if sys.version_info >= (3, 10):
+    from importlib.metadata import entry_points, EntryPoint
+else:
+    from importlib_metadata import entry_points, EntryPoint
+from typing import Type, Any, Dict, List
+
+_runtime_plugins: Dict[str, Dict[str, Type]] = {
+    'sphinxcontrib.bibtex.style.referencing': {}}
+
+
+# wrapper to work around missing type annotations for entry_points function
+def _entry_points(group: str, name: str) -> List[EntryPoint]:
+    return entry_points(group=group, name=name)  # type: ignore
 
 
 def find_plugin(group: str, name: str) -> Type[Any]:
-    """Load a sphinxcontrib-bibtex plugin."""
-    dist = pkg_resources.get_distribution('sphinxcontrib-bibtex')
-    if group not in dist.get_entry_map():
+    """Load a sphinxcontrib-bibtex plugin, either from the runtime store,
+    or from the entry points.
+    """
+    global _runtime_plugins
+    if group not in _runtime_plugins:
         raise ImportError(f"plugin group {group} not found")
-    for entry_point in pkg_resources.iter_entry_points(group, name):
-        return entry_point.load()
+    try:
+        return _runtime_plugins[group][name]
+    except KeyError:
+        for entry_point in _entry_points(group=group, name=name):
+            return entry_point.load()
     raise ImportError(f"plugin {group}.{name} not found")
 
 
 def register_plugin(group: str, name: str, klass: Type[Any],
                     force: bool = False) -> bool:
-    """Register a sphinxcontrib-bibtex plugin at runtime."""
-    dist = pkg_resources.get_distribution('sphinxcontrib-bibtex')
-    entry_map: Dict[str, Dict[str, pkg_resources.EntryPoint]] \
-        = dist.get_entry_map()
+    """Register a sphinxcontrib-bibtex plugin into the runtime store."""
+    global _runtime_plugins
+    if group not in _runtime_plugins:
+        raise ImportError(f"plugin group {group} not found")
+    eps: List[Any]
     try:
-        entry_points = entry_map[group]
+        eps = [_runtime_plugins[group][name]]
     except KeyError:
-        raise ImportError(f"plugin group {group} not found")
-    if name not in entry_points or force:
-        entry_points[name] = _FakeEntryPoint(name, klass)
+        eps = _entry_points(group=group, name=name)
+    if not eps or force:
+        _runtime_plugins[group][name] = klass
         return True
     else:
         return False

src/sphinxcontrib/bibtex/style/template.py

@@ -27,7 +27,7 @@
 from sphinxcontrib.bibtex.nodes import raw_latex
 from sphinxcontrib.bibtex.richtext import BaseReferenceText
 
-from typing import TYPE_CHECKING, Dict, Any, cast, NamedTuple
+from typing import TYPE_CHECKING, Dict, Any, cast, NamedTuple, List
 
 if TYPE_CHECKING:
     from pybtex.backends import BaseBackend
@@ -123,7 +123,7 @@ class SphinxReferenceText(BaseReferenceText[SphinxReferenceInfo]):
     for use with :class:`SphinxReferenceInfo`.
     """
 
-    def render(self, backend: "BaseBackend"):
+    def render(self, backend: "BaseBackend") -> List[docutils.nodes.Element]:
         assert isinstance(backend, pybtex_docutils.Backend), \
                "SphinxReferenceText only supports the docutils backend"
         info = self.info[0]
@@ -144,16 +144,16 @@ def render(self, backend: "BaseBackend"):
         else:
             children = super().render(backend)
             # make_refnode only takes a single child
-            refnode = make_refnode(
+            refnode2 = make_refnode(
                 builder=info.builder,
                 fromdocname=info.fromdocname,
                 todocname=info.todocname,
                 targetid=info.citation_id,
                 child=children[0],
                 title=info.title,
             )
-            refnode.extend(children[1:])  # type: ignore
-            return [refnode]
+            refnode2.extend(children[1:])  # type: ignore
+            return [refnode2]
 
 
 @node