1 files changed, 27 insertions, 0 deletions
diff --git a/sphinx/util/index_entries.py b/sphinx/util/index_entries.py
new file mode 100644
index 0000000..1004684
--- /dev/null
+++ b/sphinx/util/index_entries.py
@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+
+def split_index_msg(entry_type: str, value: str) -> list[str]:
+    # new entry types must be listed in util/nodes.py!
+    if entry_type == 'single':
+        try:
+            return _split_into(2, 'single', value)
+        except ValueError:
+            return _split_into(1, 'single', value)
+    if entry_type == 'pair':
+        return _split_into(2, 'pair', value)
+    if entry_type == 'triple':
+        return _split_into(3, 'triple', value)
+    if entry_type in {'see', 'seealso'}:
+        return _split_into(2, 'see', value)
+    msg = f'invalid {entry_type} index entry {value!r}'
+    raise ValueError(msg)
+
+
+def _split_into(n: int, type: str, value: str) -> list[str]:
+    """Split an index entry into a given number of parts at semicolons."""
+    parts = [x.strip() for x in value.split(';', n - 1)]
+    if len(list(filter(None, parts))) < n:
+        msg = f'invalid {type} index entry {value!r}'
+        raise ValueError(msg)
+    return parts