BUG: repr aligning left for string dtype columns (#54801)

Author: phofl

Diff for: doc/source/whatsnew/v2.1.0.rst

@@ -717,6 +717,7 @@ Conversion
 Strings
 ^^^^^^^
 - Bug in :meth:`Series.str` that did not raise a  ``TypeError`` when iterated (:issue:`54173`)
+- Bug in ``repr`` for :class:`DataFrame`` with string-dtype columns (:issue:`54797`)
 
 Interval
 ^^^^^^^^

Diff for: pandas/core/indexes/base.py

@@ -1397,8 +1397,8 @@ def _format_with_header(self, header: list[str_t], na_rep: str_t) -> list[str_t]
 
         values = self._values
 
-        if is_object_dtype(values.dtype):
-            values = cast(np.ndarray, values)
+        if is_object_dtype(values.dtype) or is_string_dtype(values.dtype):
+            values = np.asarray(values)
             values = lib.maybe_convert_objects(values, safe=True)
 
             result = [pprint_thing(x, escape_chars=("\t", "\r", "\n")) for x in values]

Diff for: pandas/tests/frame/test_repr_info.py

@@ -455,3 +455,14 @@ def test_masked_ea_with_formatter(self):
 0  0.12  1.00
 1  1.12  2.00"""
         assert result == expected
+
+    def test_repr_ea_columns(self, any_string_dtype):
+        # GH#54797
+        pytest.importorskip("pyarrow")
+        df = DataFrame({"long_column_name": [1, 2, 3], "col2": [4, 5, 6]})
+        df.columns = df.columns.astype(any_string_dtype)
+        expected = """   long_column_name  col2
+0                 1     4
+1                 2     5
+2                 3     6"""
+        assert repr(df) == expected