fix: raise TypeError for non-string TextCleaner inputs

haystack/components/preprocessors/text_cleaner.py

@@ -84,7 +84,11 @@ def run(self, texts: list[str]) -> dict[str, Any]:
         :param texts: List of strings to clean.
         :returns: A dictionary with the following key:
             - `texts`:  the cleaned list of strings.
+        :raises TypeError:
+            If `texts` is not a list or any element is not a string.
         """
+        if not isinstance(texts, list) or not all(isinstance(text, str) for text in texts):
+            raise TypeError("`texts` must be a list of strings.")
 
         if self._regex:
             texts = [self._regex.sub("", text) for text in texts]

releasenotes/notes/fix-text-cleaner-none-texts-d3a91c47e8b206f5.yaml

@@ -0,0 +1,5 @@
+---
+enhancements:
+  - |
+    ``TextCleaner.run`` now raises a clear ``TypeError`` when ``texts`` is not a list or any element is not a ``str``,
+    instead of failing later or producing unexpected results.

test/components/preprocessors/test_text_cleaner.py

@@ -2,6 +2,8 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+import pytest
+
 from haystack import Pipeline
 from haystack.components.preprocessors import TextCleaner
 
@@ -31,6 +33,16 @@ def test_run_with_empty_inputs():
     assert result["texts"] == []
 
 
+def test_run_rejects_invalid_inputs():
+    cleaner = TextCleaner()
+
+    with pytest.raises(TypeError):
+        cleaner.run(texts=["Hello, World!", None, 42, ""])  # type: ignore[list-item]
+
+    with pytest.raises(TypeError):
+        cleaner.run(texts=15)  # type: ignore[arg-type]
+
+
 def test_run_with_regex():
     cleaner = TextCleaner(remove_regexps=[r"\d+"])
     result = cleaner.run(texts=["Open123 Source", "HaystackAI"])