py domain: Support type union operator (PEP-604) (refs: sphinx-doc#8775)

Upgrade annotation parser for python domain to support type union
operator introduced in PEP-604.  It's available on all python
interpreters.

CHANGES

@@ -54,6 +54,7 @@ Features added
 * #8004: napoleon: Type definitions in Google style docstrings are rendered as
   references when :confval:`napoleon_preprocess_types` enabled
 * #6241: mathjax: Include mathjax.js only on the document using equations
+* #8775: py domain: Support type union operator (PEP-604)
 * #8651: std domain: cross-reference for a rubric having inline item is broken
 * #7642: std domain: Optimize case-insensitive match of term
 * #8681: viewcode: Support incremental build

sphinx/domains/python.py

@@ -100,12 +100,19 @@ def _parse_annotation(annotation: str, env: BuildEnvironment = None) -> List[Nod
     def unparse(node: ast.AST) -> List[Node]:
         if isinstance(node, ast.Attribute):
             return [nodes.Text("%s.%s" % (unparse(node.value)[0], node.attr))]
+        elif isinstance(node, ast.BinOp):
+            result = unparse(node.left)  # type: List[Node]
+            result.extend(unparse(node.op))
+            result.extend(unparse(node.right))
+            return result
+        elif isinstance(node, ast.BitOr):
+            return [addnodes.desc_sig_punctuation('', ' | ')]
         elif isinstance(node, ast.Expr):
             return unparse(node.value)
         elif isinstance(node, ast.Index):
             return unparse(node.value)
         elif isinstance(node, ast.List):
-            result = [addnodes.desc_sig_punctuation('', '[')]  # type: List[Node]
+            result = [addnodes.desc_sig_punctuation('', '[')]
             for elem in node.elts:
                 result.extend(unparse(elem))
                 result.append(addnodes.desc_sig_punctuation('', ', '))

tests/test_domain_py.py

@@ -429,6 +429,18 @@ def test_pyfunction_with_number_literals(app):
                                                         [nodes.inline, "1_6_0"])])])
 
 
+def test_pyfunction_with_union_type_operator(app):
+    text = ".. py:function:: hello(age: int | None)"
+    doctree = restructuredtext.parse(app, text)
+    assert_node(doctree[1][0][1],
+                [desc_parameterlist, ([desc_parameter, ([desc_sig_name, "age"],
+                                                        [desc_sig_punctuation, ":"],
+                                                        " ",
+                                                        [desc_sig_name, ([pending_xref, "int"],
+                                                                         [desc_sig_punctuation, " | "],
+                                                                         [pending_xref, "None"])])])])
+
+
 def test_optional_pyfunction_signature(app):
     text = ".. py:function:: compile(source [, filename [, symbol]]) -> ast object"
     doctree = restructuredtext.parse(app, text)
@@ -496,6 +508,18 @@ def test_pydata_signature_old(app):
                 domain="py", objtype="data", noindex=False)
 
 
+def test_pydata_with_union_type_operator(app):
+    text = (".. py:data:: version\n"
+            "   :type: int | str")
+    doctree = restructuredtext.parse(app, text)
+    assert_node(doctree[1][0],
+                ([desc_name, "version"],
+                 [desc_annotation, (": ",
+                                    [pending_xref, "int"],
+                                    [desc_sig_punctuation, " | "],
+                                    [pending_xref, "str"])]))
+
+
 def test_pyobject_prefix(app):
     text = (".. py:class:: Foo\n"
             "\n"