Use node.findall if available (docutils 18.x) (#403)

* use node.findall if available (docutils 18.x)

* fix test_reference

* keep test_reference backwards-compatible

* Add comments about when triage becomes unnecessary/obsolete

Co-authored-by: Jarrod Millman <jarrod.millman@gmail.com>

* whitespace

* fix docutils version as noted in docstring

Co-authored-by: Jarrod Millman <jarrod.millman@gmail.com>
Co-authored-by: Eric Larson <larson.eric.d@gmail.com>

2 files changed, 33 insertions, 7 deletions

diff --git a/numpydoc/numpydoc.py b/numpydoc/numpydoc.py
index 8210006..e656fb5 100644
--- a/numpydoc/numpydoc.py
+++ b/numpydoc/numpydoc.py
@@ -43,6 +43,19 @@ logger = logging.getLogger(__name__)
 HASH_LEN = 12
 
 
+def _traverse_or_findall(node, condition, **kwargs):
+    """Triage node.traverse (docutils <0.18.1) vs node.findall.
+
+    TODO: This check can be removed when the minimum supported docutils version
+    for numpydoc is docutils>=0.18.1
+    """
+    return (
+        node.findall(condition, **kwargs)
+        if hasattr(node, "findall")
+        else node.traverse(condition, **kwargs)
+    )
+
+
 def rename_references(app, what, name, obj, options, lines):
     # decorate reference numbers so that there are no duplicates
     # these are later undecorated in the doctree, in relabel_references
@@ -81,8 +94,12 @@ def _is_cite_in_numpydoc_docstring(citation_node):
             return False
 
     sibling_sections = itertools.chain(
-        section_node.traverse(
-            is_docstring_section, include_self=True, descend=False, siblings=True
+        _traverse_or_findall(
+            section_node,
+            is_docstring_section,
+            include_self=True,
+            descend=False,
+            siblings=True,
         )
     )
     for sibling_section in sibling_sections:
@@ -101,7 +118,7 @@ def _is_cite_in_numpydoc_docstring(citation_node):
 
 def relabel_references(app, doc):
     # Change 'hash-ref' to 'ref' in label text
-    for citation_node in doc.traverse(citation):
+    for citation_node in _traverse_or_findall(doc, citation):
         if not _is_cite_in_numpydoc_docstring(citation_node):
             continue
         label_node = citation_node[0]
@@ -121,7 +138,7 @@ def relabel_references(app, doc):
                     and node[0].astext() == f"[{ref_text}]"
                 )
 
-            for xref_node in ref.parent.traverse(matching_pending_xref):
+            for xref_node in _traverse_or_findall(ref.parent, matching_pending_xref):
                 xref_node.replace(xref_node[0], Text(f"[{new_text}]"))
             ref.replace(ref_text, new_text.copy())
 
@@ -129,10 +146,10 @@ def relabel_references(app, doc):
 def clean_backrefs(app, doc, docname):
     # only::latex directive has resulted in citation backrefs without reference
     known_ref_ids = set()
-    for ref in doc.traverse(reference, descend=True):
+    for ref in _traverse_or_findall(doc, reference, descend=True):
         for id_ in ref["ids"]:
             known_ref_ids.add(id_)
-    for citation_node in doc.traverse(citation, descend=True):
+    for citation_node in _traverse_or_findall(doc, citation, descend=True):
         # remove backrefs to non-existent refs
         citation_node["backrefs"] = [
             id_ for id_ in citation_node["backrefs"] if id_ in known_ref_ids
diff --git a/numpydoc/tests/test_full.py b/numpydoc/tests/test_full.py
index e0defe2..c4ae134 100644
--- a/numpydoc/tests/test_full.py
+++ b/numpydoc/tests/test_full.py
@@ -1,11 +1,13 @@
 import os.path as op
 import re
 import shutil
+from packaging import version
 
 import pytest
 import sphinx
 from sphinx.application import Sphinx
 from sphinx.util.docutils import docutils_namespace
+from docutils import __version__ as docutils_version
 
 
 # Test framework adapted from sphinx-gallery (BSD 3-clause)
@@ -89,7 +91,14 @@ def test_reference(sphinx_app, html_file, expected_length):
     with open(op.join(out_dir, *html_file)) as fid:
         html = fid.read()
 
-    reference_list = re.findall(r'<a class="fn-backref" href="\#id\d+">(.*)<\/a>', html)
+    # TODO: This check can be removed when the minimum supported docutils version
+    # for numpydoc is docutils>=0.18
+    pattern = (
+        'role="doc-backlink"'
+        if version.parse(docutils_version) >= version.parse("0.18")
+        else 'class="fn-backref"'
+    )
+    reference_list = re.findall(rf'<a {pattern} href="\#id\d+">(.*)<\/a>', html)
 
     assert len(reference_list) == expected_length
     for ref in reference_list: