core[patch]: improve comma separated list output parser to handle non-space separated list (#20434)

- **Description:** Changes
`lanchain_core.output_parsers.CommaSeparatedListOutputParser` to handle
`,` as a delimiter alongside the previous implementation which used `, `
as delimiter.
- **Issue:** Started noticing that some results returned by LLMs were
not getting parsed correctly when the output contained `,` instead of `,
`.
  - **Dependencies:** No
  - **Twitter handle:** not active on twitter.


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libs/core/langchain_core/output_parsers/list.py

@@ -115,12 +115,12 @@ class CommaSeparatedListOutputParser(ListOutputParser):
     def get_format_instructions(self) -> str:
         return (
             "Your response should be a list of comma separated values, "
-            "eg: `foo, bar, baz`"
+            "eg: `foo, bar, baz` or `foo,bar,baz`"
         )
 
     def parse(self, text: str) -> List[str]:
         """Parse the output of an LLM call."""
-        return text.strip().split(", ")
+        return [part.strip() for part in text.split(",")]
 
     @property
     def _type(self) -> str:

libs/core/tests/unit_tests/output_parsers/test_list_parser.py

@@ -26,10 +26,29 @@ def test_single_item() -> None:
     assert list(parser.transform(iter([text]))) == [[a] for a in expected]
 
 
+def test_multiple_items_with_spaces() -> None:
+    """Test that a string with multiple comma-separated items
+    with spaces is parsed to a list."""
+    parser = CommaSeparatedListOutputParser()
+    text = "foo, bar, baz"
+    expected = ["foo", "bar", "baz"]
+
+    assert parser.parse(text) == expected
+    assert add(parser.transform(t for t in text)) == expected
+    assert list(parser.transform(t for t in text)) == [[a] for a in expected]
+    assert list(parser.transform(t for t in text.splitlines(keepends=True))) == [
+        [a] for a in expected
+    ]
+    assert list(
+        parser.transform(" " + t if i > 0 else t for i, t in enumerate(text.split(" ")))
+    ) == [[a] for a in expected]
+    assert list(parser.transform(iter([text]))) == [[a] for a in expected]
+
+
 def test_multiple_items() -> None:
     """Test that a string with multiple comma-separated items is parsed to a list."""
     parser = CommaSeparatedListOutputParser()
-    text = "foo, bar, baz"
+    text = "foo,bar,baz"
     expected = ["foo", "bar", "baz"]
 
     assert parser.parse(text) == expected