[Doc] Add github links for source code references (#10672)

Signed-off-by: Russell Bryant <rbryant@redhat.com>
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Co-authored-by: DarkLight1337 <tlleungac@connect.ust.hk>

docs/requirements-docs.txt

@@ -17,3 +17,4 @@ aiohttp
 starlette
 openai # Required by docs/source/serving/openai_compatible_server.md's vllm.entrypoints.openai.cli_args
 partial-json-parser # Required by docs/source/serving/openai_compatible_server.md's vllm.entrypoints.openai.cli_args
+requests

docs/source/conf.py

@@ -10,11 +10,13 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 
+import inspect
 import logging
 import os
 import sys
 from typing import List
 
+import requests
 from sphinx.ext import autodoc
 
 logger = logging.getLogger(__name__)
@@ -34,6 +36,7 @@ author = 'the vLLM Team'
 extensions = [
     "sphinx.ext.napoleon",
     "sphinx.ext.viewcode",
+    "sphinx.ext.linkcode",
     "sphinx.ext.intersphinx",
     "sphinx_copybutton",
     "sphinx.ext.autodoc",
@@ -94,6 +97,69 @@ def setup(app):
     generate_examples()
 
 
+_cached_base: str = ""
+_cached_branch: str = ""
+
+
+def get_repo_base_and_branch(pr_number):
+    global _cached_base, _cached_branch
+    if _cached_base and _cached_branch:
+        return _cached_base, _cached_branch
+
+    url = f"https://api.github.com/repos/vllm-project/vllm/pulls/{pr_number}"
+    response = requests.get(url)
+    if response.status_code == 200:
+        data = response.json()
+        _cached_base = data['head']['repo']['full_name']
+        _cached_branch = data['head']['ref']
+        return _cached_base, _cached_branch
+    else:
+        logger.error("Failed to fetch PR details: %s", response)
+        return None, None
+
+
+def linkcode_resolve(domain, info):
+    if domain != 'py':
+        return None
+    if not info['module']:
+        return None
+    filename = info['module'].replace('.', '/')
+    module = info['module']
+
+    # try to determine the correct file and line number to link to
+    obj = sys.modules[module]
+
+    # get as specific as we can
+    lineno: int = 0
+    filename: str = ""
+    try:
+        for part in info['fullname'].split('.'):
+            obj = getattr(obj, part)
+
+            if not (inspect.isclass(obj) or inspect.isfunction(obj)
+                    or inspect.ismethod(obj)):
+                obj = obj.__class__  # Get the class of the instance
+
+            lineno = inspect.getsourcelines(obj)[1]
+            filename = (inspect.getsourcefile(obj)
+                        or f"{filename}.py").split("vllm/", 1)[1]
+    except Exception:
+        # For some things, like a class member, won't work, so
+        # we'll use the line number of the parent (the class)
+        pass
+
+    if filename.startswith("checkouts/"):
+        # a PR build on readthedocs
+        pr_number = filename.split("/")[1]
+        filename = filename.split("/", 2)[2]
+        base, branch = get_repo_base_and_branch(pr_number)
+        if base and branch:
+            return f"https://github.com/{base}/blob/{branch}/{filename}#L{lineno}"
+
+    # Otherwise, link to the source file on the main branch
+    return f"https://github.com/vllm-project/vllm/blob/main/{filename}#L{lineno}"
+
+
 # Mock out external dependencies here, otherwise the autodoc pages may be blank.
 autodoc_mock_imports = [
     "compressed_tensors",