From 39d71a8ddd1fb5a3a58f8802591b08294110b853 Mon Sep 17 00:00:00 2001
From: Lengshuang <90967079+Lesereingrape@users.noreply.github.com>
Date: Sat, 26 Sep 2026 14:17:43 +0800
Subject: [PATCH 1/2] fix(csv): reject an unsupported conversion_mode instead
 of falling into row mode

CSVToDocument compared conversion_mode only against "file" in run(), so any
other value selected the row branch: a typo such as "Rows" silently produced
one Document per row instead of one per file, and a value differing only by
trailing whitespace raised an error claiming conversion_mode='row'. Validate
the Literal in __init__, the way the sibling XLSXToDocument already validates
table_format and link_format.
---
 haystack/components/converters/csv.py            |  2 ++
 ...version-mode-validation-8f4c2b1d7e9a3056.yaml |  9 +++++++++
 .../converters/test_csv_to_document.py           | 16 ++++++++++++++++
 3 files changed, 27 insertions(+)
 create mode 100644 releasenotes/notes/csv-conversion-mode-validation-8f4c2b1d7e9a3056.yaml

diff --git a/haystack/components/converters/csv.py b/haystack/components/converters/csv.py
index 9a4a102da54..eaa70bcfdc4 100644
--- a/haystack/components/converters/csv.py
+++ b/haystack/components/converters/csv.py
@@ -77,6 +77,8 @@ def __init__(
         self.quotechar = quotechar
 
         # Basic validation
+        if conversion_mode not in ("file", "row"):
+            raise ValueError(f"CSVToDocument: unsupported conversion_mode {conversion_mode!r}. Choose 'file' or 'row'.")
         if len(self.delimiter) != 1:
             raise ValueError("CSVToDocument: delimiter must be a single character.")
         if len(self.quotechar) != 1:
diff --git a/releasenotes/notes/csv-conversion-mode-validation-8f4c2b1d7e9a3056.yaml b/releasenotes/notes/csv-conversion-mode-validation-8f4c2b1d7e9a3056.yaml
new file mode 100644
index 00000000000..c5bade60d64
--- /dev/null
+++ b/releasenotes/notes/csv-conversion-mode-validation-8f4c2b1d7e9a3056.yaml
@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    ``CSVToDocument`` now rejects an unsupported ``conversion_mode`` in its constructor.
+    Previously the value was only compared against ``"file"`` in ``run()``, so any other
+    string, including a typo such as ``"Rows"`` or a value with a trailing space, silently
+    selected the row mode and produced one ``Document`` per row instead of one per file.
+    When ``content_column`` was not passed, the raised error also reported
+    ``conversion_mode='row'`` for a component the caller had never configured that way.
diff --git a/test/components/converters/test_csv_to_document.py b/test/components/converters/test_csv_to_document.py
index dfb6afcdd65..caea76fe3d5 100644
--- a/test/components/converters/test_csv_to_document.py
+++ b/test/components/converters/test_csv_to_document.py
@@ -190,6 +190,22 @@ def test_init_validates_delimiter_and_quotechar(self):
         with pytest.raises(ValueError):
             CSVToDocument(quotechar='""')
 
+    def test_init_rejects_an_unknown_conversion_mode(self):
+        # A typo must not silently switch the component into row mode: run() dispatches on the value
+        # and anything that is not "file" falls through to the row branch.
+        with pytest.raises(ValueError, match="unsupported conversion_mode 'Rows'"):
+            CSVToDocument(conversion_mode="Rows")
+
+    def test_init_rejects_a_conversion_mode_that_only_differs_in_whitespace_or_case(self):
+        with pytest.raises(ValueError, match="unsupported conversion_mode 'file '"):
+            CSVToDocument(conversion_mode="file ")
+        with pytest.raises(ValueError, match="unsupported conversion_mode ''"):
+            CSVToDocument(conversion_mode="")
+
+    def test_init_accepts_both_documented_conversion_modes(self):
+        assert CSVToDocument(conversion_mode="file").conversion_mode == "file"
+        assert CSVToDocument(conversion_mode="row").conversion_mode == "row"
+
     def test_row_mode_large_file_warns(self, caplog, monkeypatch):
         # Make the threshold tiny so the warning always triggers.
         import haystack.components.converters.csv as csv_mod

From 1ac6e39a594504ff4847fc7f97f186d13596b1cd Mon Sep 17 00:00:00 2001
From: Lesereingrape <lesereingrape@users.noreply.github.com>
Date: Fri, 2 Oct 2026 18:23:53 +0800
Subject: [PATCH 2/2] test(csv): annotate invalid conversion_mode calls for
 mypy

---
 test/components/converters/test_csv_to_document.py | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/test/components/converters/test_csv_to_document.py b/test/components/converters/test_csv_to_document.py
index caea76fe3d5..c79d74e9f31 100644
--- a/test/components/converters/test_csv_to_document.py
+++ b/test/components/converters/test_csv_to_document.py
@@ -191,16 +191,14 @@ def test_init_validates_delimiter_and_quotechar(self):
             CSVToDocument(quotechar='""')
 
     def test_init_rejects_an_unknown_conversion_mode(self):
-        # A typo must not silently switch the component into row mode: run() dispatches on the value
-        # and anything that is not "file" falls through to the row branch.
         with pytest.raises(ValueError, match="unsupported conversion_mode 'Rows'"):
-            CSVToDocument(conversion_mode="Rows")
+            CSVToDocument(conversion_mode="Rows")  # type: ignore[arg-type]
 
     def test_init_rejects_a_conversion_mode_that_only_differs_in_whitespace_or_case(self):
         with pytest.raises(ValueError, match="unsupported conversion_mode 'file '"):
-            CSVToDocument(conversion_mode="file ")
+            CSVToDocument(conversion_mode="file ")  # type: ignore[arg-type]
         with pytest.raises(ValueError, match="unsupported conversion_mode ''"):
-            CSVToDocument(conversion_mode="")
+            CSVToDocument(conversion_mode="")  # type: ignore[arg-type]
 
     def test_init_accepts_both_documented_conversion_modes(self):
         assert CSVToDocument(conversion_mode="file").conversion_mode == "file"