Fix display of union "short" type annotations in Sphinx

This applies to `a | b` annotations in Python before 3.10. See jbms/sphinx-immaterial#161

docs/conf.py

@@ -366,6 +366,26 @@ def classproperty(obj):
  setattr(galois._fields._meta.FieldArrayMeta, p, FieldArrayMeta_property)
 
 
+def autodoc_process_signature(app, what, name, obj, options, signature, return_annotation):
+ signature = modify_type_hints(signature)
+ return_annotation = modify_type_hints(return_annotation)
+ return signature, return_annotation
+
+
+def modify_type_hints(signature):
+ """
+ Fix shortening numpy type annotations in string annotations created with
+ `from __future__ import annotations` that Sphinx can't process before Python
+ 3.10.
+
+ See https://github.com/jbms/sphinx-immaterial/issues/161
+ """
+ if signature:
+ signature = signature.replace("np", "~numpy")
+ return signature
+
+
 def setup(app):
  app.connect("autodoc-skip-member", autodoc_skip_member)
  app.connect("autodoc-process-bases", autodoc_process_bases)
+ app.connect("autodoc-process-signature", autodoc_process_signature)