1 files changed, 70 insertions, 0 deletions
diff --git a/sphinx/environment/collectors/metadata.py b/sphinx/environment/collectors/metadata.py
new file mode 100644
index 0000000..5f737a9
--- /dev/null
+++ b/sphinx/environment/collectors/metadata.py
@@ -0,0 +1,70 @@
+"""The metadata collector components for sphinx.environment."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, cast
+
+from docutils import nodes
+
+from sphinx.environment.collectors import EnvironmentCollector
+
+if TYPE_CHECKING:
+    from sphinx.application import Sphinx
+    from sphinx.environment import BuildEnvironment
+
+
+class MetadataCollector(EnvironmentCollector):
+    """metadata collector for sphinx.environment."""
+
+    def clear_doc(self, app: Sphinx, env: BuildEnvironment, docname: str) -> None:
+        env.metadata.pop(docname, None)
+
+    def merge_other(self, app: Sphinx, env: BuildEnvironment,
+                    docnames: set[str], other: BuildEnvironment) -> None:
+        for docname in docnames:
+            env.metadata[docname] = other.metadata[docname]
+
+    def process_doc(self, app: Sphinx, doctree: nodes.document) -> None:
+        """Process the docinfo part of the doctree as metadata.
+
+        Keep processing minimal -- just return what docutils says.
+        """
+        index = doctree.first_child_not_matching_class(nodes.PreBibliographic)
+        if index is None:
+            return
+        elif isinstance(doctree[index], nodes.docinfo):
+            md = app.env.metadata[app.env.docname]
+            for node in doctree[index]:  # type: ignore[attr-defined]
+                # nodes are multiply inherited...
+                if isinstance(node, nodes.authors):
+                    authors = cast(list[nodes.author], node)
+                    md['authors'] = [author.astext() for author in authors]
+                elif isinstance(node, nodes.field):
+                    assert len(node) == 2
+                    field_name = cast(nodes.field_name, node[0])
+                    field_body = cast(nodes.field_body, node[1])
+                    md[field_name.astext()] = field_body.astext()
+                elif isinstance(node, nodes.TextElement):
+                    # other children must be TextElement
+                    # see: https://docutils.sourceforge.io/docs/ref/doctree.html#bibliographic-elements  # noqa: E501
+                    md[node.__class__.__name__] = node.astext()
+
+            for name, value in md.items():
+                if name in ('tocdepth',):
+                    try:
+                        value = int(value)
+                    except ValueError:
+                        value = 0
+                    md[name] = value
+
+            doctree.pop(index)
+
+
+def setup(app: Sphinx) -> dict[str, Any]:
+    app.add_env_collector(MetadataCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }