Treat a non-finite token count as unrecorded

`float("inf") > 0` is true, so a stored `"inf"` was preserved as if it
were a real count and reached the UI as "∞". Require a finite positive
value, which also covers `nan` explicitly rather than by accident.

docsgpt/api/user/sources/chunks.py

@@ -1,5 +1,7 @@
 """Source document management chunk management."""
 
+import math
+
 from flask import current_app, jsonify, make_response, request
 from flask_restx import fields, Namespace, Resource
 
@@ -48,22 +50,24 @@ def _has_usable_token_count(metadata: dict) -> bool:
 
     Stores round-trip metadata differently -- pgvector keeps JSON types, the
     Mongo backend can hand back strings -- so a numeric string counts as
-    recorded. Anything else (missing, empty, non-numeric, zero or negative)
-    does not.
+    recorded. Anything else (missing, empty, non-numeric, zero, negative, or
+    non-finite) does not: ``float("inf")`` is greater than zero but is not a
+    number of tokens, and it reaches ``toLocaleString`` in the UI as "∞".
 
     Args:
         metadata: A chunk's metadata mapping.
 
     Returns:
-        True when ``token_count`` holds a positive number.
+        True when ``token_count`` holds a finite positive number.
     """
     raw = metadata.get("token_count")
     if isinstance(raw, bool) or not isinstance(raw, (int, float, str)):
         return False
     try:
-        return float(raw) > 0
+        value = float(raw)
     except (TypeError, ValueError):
         return False
+    return math.isfinite(value) and value > 0
 
 
 def _with_token_counts(chunks: list) -> list:

tests/api/user/sources/test_chunks.py

@@ -199,7 +199,10 @@ class TestGetChunks:
         # An already-recorded count is left alone, whatever tokenizer produced it.
         assert chunks[2]["metadata"]["token_count"] == 42
 
-    @pytest.mark.parametrize("stored", ["", 0, -1, "abc", None, {"n": 1}])
+    @pytest.mark.parametrize(
+        "stored",
+        ["", 0, -1, "abc", None, {"n": 1}, "inf", "-inf", "nan", float("inf")],
+    )
     def test_recomputes_unusable_token_count(self, app, pg_conn, stored):
         from docsgpt.api.user.sources.chunks import GetChunks