text splitters: add chunk_size and chunk_overlap validations (#31916)

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libs/text-splitters/langchain_text_splitters/base.py

@@ -47,6 +47,12 @@ class TextSplitter(BaseDocumentTransformer, ABC):
             strip_whitespace: If `True`, strips whitespace from the start and end of
                               every document
         """
+        if chunk_size <= 0:
+            msg = f"chunk_size must be > 0, got {chunk_size}"
+            raise ValueError(msg)
+        if chunk_overlap < 0:
+            msg = f"chunk_overlap must be >= 0, got {chunk_overlap}"
+            raise ValueError(msg)
         if chunk_overlap > chunk_size:
             msg = (
                 f"Got a larger chunk overlap ({chunk_overlap}) than chunk size "

libs/text-splitters/tests/unit_tests/test_text_splitters.py

@@ -212,6 +212,11 @@ def test_character_text_splitting_args() -> None:
     """Test invalid arguments."""
     with pytest.raises(ValueError):
         CharacterTextSplitter(chunk_size=2, chunk_overlap=4)
+    for invalid_size in (0, -1):
+        with pytest.raises(ValueError):
+            CharacterTextSplitter(chunk_size=invalid_size)
+    with pytest.raises(ValueError):
+        CharacterTextSplitter(chunk_size=2, chunk_overlap=-1)
 
 
 def test_merge_splits() -> None: