DOC: add linkcode to docs

docs/cudf/source/conf.py

@@ -19,10 +19,12 @@
 import datetime
 import filecmp
 import glob
+import inspect
 import os
 import re
 import sys
 import tempfile
+import warnings
 import xml.etree.ElementTree as ET
 
 from docutils.nodes import Text
@@ -69,6 +71,7 @@ class PseudoLexer(RegexLexer):
     "sphinx.ext.autosummary",
     "sphinx_copybutton",
     "sphinx_remove_toctrees",
+    "sphinx.ext.linkcode",
     "numpydoc",
     "IPython.sphinxext.ipython_console_highlighting",
     "IPython.sphinxext.ipython_directive",
@@ -557,6 +560,67 @@ def on_missing_reference(app, env, node, contnode):
 ]
 
 
+# Needed for the [source] button on the API docs to link to the github code
+# based on pandas doc/source/conf.py
+def linkcode_resolve(domain, info) -> str | None:
+    """
+    Determine the URL corresponding to Python object
+    """
+    if domain != "py":
+        return None
+
+    modname = info["module"]
+    fullname = info["fullname"]
+
+    submod = sys.modules.get(modname)
+    if submod is None:
+        return None
+
+    obj = submod
+    for part in fullname.split("."):
+        try:
+            with warnings.catch_warnings():
+                # Accessing deprecated objects will generate noisy warnings
+                warnings.simplefilter("ignore", FutureWarning)
+                obj = getattr(obj, part)
+        except AttributeError:
+            return None
+
+    try:
+        fn = inspect.getsourcefile(inspect.unwrap(obj))
+    except TypeError:
+        try:  # property
+            fn = inspect.getsourcefile(inspect.unwrap(obj.fget))
+        except (AttributeError, TypeError):
+            fn = None
+    if not fn:
+        return None
+
+    try:
+        source, lineno = inspect.getsourcelines(obj)
+    except TypeError:
+        try:  # property
+            source, lineno = inspect.getsourcelines(obj.fget)
+        except (AttributeError, TypeError):
+            lineno = None
+    except OSError:
+        lineno = None
+
+    if lineno:
+        linespec = f"#L{lineno}-L{lineno + len(source) - 1}"
+    else:
+        linespec = ""
+
+    fn = os.path.relpath(fn, start=os.path.dirname(cudf.__file__))
+    if "+" in cudf.__version__:
+        return f"https://github.com/rapidsai/cudf/blob/main/cudf/{fn}{linespec}"
+    else:
+        return (
+            f"https://github.com/rapidsai/cudf/blob/"
+            f"branch-{version}/python/cudf/cudf/{fn}{linespec}"
+        )
+
+
 def setup(app):
     app.add_css_file("https://docs.rapids.ai/assets/css/custom.css")
     app.add_js_file(