Automatically add links to API docs for matching strings in docs (#37434)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/mkdocs/hooks/autoref_code.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""
+MkDocs hook to automatically convert inline code references to API doc links.
+
+For example, `WeightTransferConfig` becomes
+[`WeightTransferConfig`][vllm.config.WeightTransferConfig]
+
+This works with the `autorefs` plugin to create clickable cross-references
+to API documentation pages generated by `mkdocstrings`.
+
+The hook builds an index of all documented public Python names (classes and
+functions with docstrings) from the vllm package at startup using AST parsing,
+then substitutes matching inline code spans on each page. Names without
+docstrings are excluded because mkdocstrings will not generate a page for them.
+"""
+
+import ast
+import logging
+from pathlib import Path
+
+import regex as re
+from mkdocs.config.defaults import MkDocsConfig
+from mkdocs.structure.files import Files
+from mkdocs.structure.pages import Page
+
+logger = logging.getLogger("mkdocs")
+
+ROOT_DIR = Path(__file__).parent.parent.parent.parent.resolve()
+VLLM_DIR = ROOT_DIR / "vllm"
+
+# Maps short name -> qualified name (e.g. "ModelConfig" -> "vllm.config.ModelConfig")
+_name_index: dict[str, str] = {}
+
+# Fenced code block pattern (``` or ~~~, with optional language specifier).
+_FENCED_BLOCK = re.compile(
+    r"(?:^|\n)(?P<fence>`{3,}|~{3,})[^\n]*\n.*?(?:\n(?P=fence))", re.DOTALL
+)
+
+# Inline code that is NOT already part of a markdown link.
+# Matches `Name` but not [`Name`] and not [`Name`][...] or [`Name`](...).
+_INLINE_CODE = re.compile(
+    r"(?<!\[)"  # not preceded by [
+    r"`(?P<name>[A-Za-z0-9_]*)`"  # `UpperCamelCase` or `UPPER_SNAKE`
+    r"(?!\])"  # not followed by ]
+)
+
+
+def _has_docstring(node: ast.AST) -> bool:
+    """Check if a class or function node has a docstring."""
+    if not isinstance(node, ast.ClassDef | ast.FunctionDef | ast.AsyncFunctionDef):
+        return False
+    return ast.get_docstring(node, clean=False) is not None
+
+
+def _module_path(filepath: Path) -> str:
+    """Convert a filesystem path to a dotted module path."""
+    rel = filepath.relative_to(ROOT_DIR)
+    parts = list(rel.with_suffix("").parts)
+    if parts[-1] == "__init__":
+        parts = parts[:-1]
+    return ".".join(parts)
+
+
+def _index_file(filepath: Path) -> dict[str, str]:
+    """Extract documented public names from a Python file using AST parsing.
+
+    Only classes and functions with docstrings are included, since
+    mkdocstrings won't generate a page for undocumented symbols.
+    """
+    names: dict[str, str] = {}
+    try:
+        source = filepath.read_text(encoding="utf-8")
+        tree = ast.parse(source, filename=str(filepath))
+    except (SyntaxError, UnicodeDecodeError):
+        return names
+
+    module = _module_path(filepath)
+
+    for node in ast.iter_child_nodes(tree):
+        if (
+            # Class definitions (with docstring)
+            isinstance(node, ast.ClassDef)
+            and not node.name.startswith("_")
+            and _has_docstring(node)
+        ) or (
+            # Function definitions (with docstring, only uppercase/CamelCase)
+            isinstance(node, ast.FunctionDef | ast.AsyncFunctionDef)
+            and not node.name.startswith("_")
+            and node.name[0].isupper()
+            and _has_docstring(node)
+        ):
+            names[node.name] = f"{module}.{node.name}"
+
+    return names
+
+
+def _build_index() -> dict[str, str]:
+    """Walk the vllm package and build a name -> qualified path index."""
+    index: dict[str, str] = {}
+    # Track conflicts: if multiple modules define the same name,
+    # prefer shallower modules (more likely to be the public API).
+    depth: dict[str, int] = {}
+
+    for filepath in sorted(VLLM_DIR.rglob("*.py")):
+        # Skip internal/private modules
+        if any(part.startswith("_") and part != "__init__" for part in filepath.parts):
+            continue
+        # Skip third-party vendored code
+        rel = filepath.relative_to(VLLM_DIR)
+        if rel.parts and rel.parts[0] in ("third_party", "vllm_flash_attn"):
+            continue
+
+        module_depth = len(filepath.relative_to(ROOT_DIR).parts)
+        file_names = _index_file(filepath)
+
+        for name, qualified in file_names.items():
+            if name not in index or module_depth < depth[name]:
+                index[name] = qualified
+                depth[name] = module_depth
+
+    return index
+
+
+def on_startup(*, command: str, dirty: bool) -> None:
+    """Build the name index once at startup."""
+    global _name_index
+    _name_index = _build_index()
+    logger.info("autoref_code: indexed %d names from vllm/", len(_name_index))
+
+
+def on_page_markdown(
+    markdown: str, *, page: Page, config: MkDocsConfig, files: Files
+) -> str:
+    """Replace inline code references with autoref links."""
+    if not _name_index:
+        return markdown
+
+    # Skip API reference pages to avoid circular/redundant links.
+    if page.file.src_path.startswith("api/"):
+        return markdown
+
+    # Step 1: Mask fenced code blocks so we don't touch code inside them.
+    masks: list[str] = []
+
+    def _mask_block(match: re.Match) -> str:
+        masks.append(match.group(0))
+        return f"\ue000CODEBLOCK{len(masks) - 1}\ue000"
+
+    masked = _FENCED_BLOCK.sub(_mask_block, markdown)
+
+    # Step 2: Replace inline code references.
+    def _replace(match: re.Match) -> str:
+        name = match.group("name")
+        qualified = _name_index.get(name)
+        if qualified is None:
+            return match.group(0)
+        logger.debug("autoref_code: linking `%s` to [%s]", name, qualified)
+        return f"[`{name}`][{qualified}]"
+
+    result = _INLINE_CODE.sub(_replace, masked)
+
+    # Step 3: Restore masked code blocks.
+    result = re.sub(
+        r"\ue000CODEBLOCK(\d+)\ue000", lambda m: masks[int(m.group(1))], result
+    )
+    return result

mkdocs.yaml

@@ -54,6 +54,7 @@ hooks:
   - docs/mkdocs/hooks/generate_argparse.py
   - docs/mkdocs/hooks/generate_metrics.py
   - docs/mkdocs/hooks/url_schemes.py
+  - docs/mkdocs/hooks/autoref_code.py
 
 plugins:
   - meta