[3.13] GH-121970: Extract pydoc_topics into a new extension (#129116) (#130441)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Doc/tools/extensions/pydoc_topics.py

@@ -0,0 +1,187 @@
+"""Support for building "topic help" for pydoc."""
+
+from __future__ import annotations
+
+from time import asctime
+from typing import TYPE_CHECKING
+
+from sphinx.builders.text import TextBuilder
+from sphinx.util import logging
+from sphinx.util.display import status_iterator
+from sphinx.util.docutils import new_document
+from sphinx.writers.text import TextTranslator
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence, Set
+
+    from sphinx.application import Sphinx
+    from sphinx.util.typing import ExtensionMetadata
+
+logger = logging.getLogger(__name__)
+
+_PYDOC_TOPIC_LABELS: Sequence[str] = sorted({
+    "assert",
+    "assignment",
+    "assignment-expressions",
+    "async",
+    "atom-identifiers",
+    "atom-literals",
+    "attribute-access",
+    "attribute-references",
+    "augassign",
+    "await",
+    "binary",
+    "bitwise",
+    "bltin-code-objects",
+    "bltin-ellipsis-object",
+    "bltin-null-object",
+    "bltin-type-objects",
+    "booleans",
+    "break",
+    "callable-types",
+    "calls",
+    "class",
+    "comparisons",
+    "compound",
+    "context-managers",
+    "continue",
+    "conversions",
+    "customization",
+    "debugger",
+    "del",
+    "dict",
+    "dynamic-features",
+    "else",
+    "exceptions",
+    "execmodel",
+    "exprlists",
+    "floating",
+    "for",
+    "formatstrings",
+    "function",
+    "global",
+    "id-classes",
+    "identifiers",
+    "if",
+    "imaginary",
+    "import",
+    "in",
+    "integers",
+    "lambda",
+    "lists",
+    "naming",
+    "nonlocal",
+    "numbers",
+    "numeric-types",
+    "objects",
+    "operator-summary",
+    "pass",
+    "power",
+    "raise",
+    "return",
+    "sequence-types",
+    "shifting",
+    "slicings",
+    "specialattrs",
+    "specialnames",
+    "string-methods",
+    "strings",
+    "subscriptions",
+    "truth",
+    "try",
+    "types",
+    "typesfunctions",
+    "typesmapping",
+    "typesmethods",
+    "typesmodules",
+    "typesseq",
+    "typesseq-mutable",
+    "unary",
+    "while",
+    "with",
+    "yield",
+})
+
+
+class PydocTopicsBuilder(TextBuilder):
+    name = "pydoc-topics"
+
+    def init(self) -> None:
+        super().init()
+        self.topics: dict[str, str] = {}
+
+    def get_outdated_docs(self) -> str:
+        # Return a string describing what an update build will build.
+        return "all pydoc topics"
+
+    def write_documents(self, _docnames: Set[str]) -> None:
+        env = self.env
+
+        labels: dict[str, tuple[str, str, str]]
+        labels = env.domains.standard_domain.labels
+
+        # docname -> list of (topic_label, label_id) pairs
+        doc_labels: dict[str, list[tuple[str, str]]] = {}
+        for topic_label in _PYDOC_TOPIC_LABELS:
+            try:
+                docname, label_id, _section_name = labels[topic_label]
+            except KeyError:
+                logger.warning("label %r not in documentation", topic_label)
+                continue
+            doc_labels.setdefault(docname, []).append((topic_label, label_id))
+
+        for docname, label_ids in status_iterator(
+            doc_labels.items(),
+            "building topics... ",
+            length=len(doc_labels),
+            stringify_func=_display_labels,
+        ):
+            doctree = env.get_and_resolve_doctree(docname, builder=self)
+            doc_ids = doctree.ids
+            for topic_label, label_id in label_ids:
+                document = new_document("<section node>")
+                document.append(doc_ids[label_id])
+                visitor = TextTranslator(document, builder=self)
+                document.walkabout(visitor)
+                self.topics[topic_label] = visitor.body
+
+    def finish(self) -> None:
+        topics_repr = "\n".join(
+            f"    '{topic}': {_repr(self.topics[topic])},"
+            for topic in sorted(self.topics)
+        )
+        topics = f"""\
+# Autogenerated by Sphinx on {asctime()}
+# as part of the release process.
+
+topics = {{
+{topics_repr}
+}}
+"""
+        self.outdir.joinpath("topics.py").write_text(topics, encoding="utf-8")
+
+
+def _display_labels(item: tuple[str, Sequence[tuple[str, str]]]) -> str:
+    _docname, label_ids = item
+    labels = [name for name, _id in label_ids]
+    if len(labels) > 4:
+        return f"{labels[0]}, {labels[1]}, ..., {labels[-2]}, {labels[-1]}"
+    return ", ".join(labels)
+
+
+def _repr(text: str, /) -> str:
+    """Return a triple-single-quoted representation of text."""
+    if "'''" not in text:
+        return f"r'''{text}'''"
+    text = text.replace("\\", "\\\\").replace("'''", r"\'\'\'")
+    return f"'''{text}'''"
+
+
+def setup(app: Sphinx) -> ExtensionMetadata:
+    app.add_builder(PydocTopicsBuilder)
+
+    return {
+        "version": "1.0",
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }