Backport PR pandas-dev#51548: BUG: parsing pyarrow dtypes corner case

Author: jbrockmendel

doc/source/whatsnew/v2.0.0.rst

@@ -1417,7 +1417,7 @@ Metadata
 
 Other
 ^^^^^
-
+- Bug in incorrectly accepting dtype strings containing "[pyarrow]" more than once (:issue:`51548`)
 - Bug in :meth:`Series.searchsorted` inconsistent behavior when accepting :class:`DataFrame` as parameter ``value`` (:issue:`49620`)
 - Bug in :func:`array` failing to raise on :class:`DataFrame` inputs (:issue:`51167`)
 

pandas/core/arrays/arrow/dtype.py

@@ -197,7 +197,8 @@ def construct_from_string(cls, string: str) -> ArrowDtype:
         if string == "string[pyarrow]":
             # Ensure Registry.find skips ArrowDtype to use StringDtype instead
             raise TypeError("string[pyarrow] should be constructed by StringDtype")
-        base_type = string.split("[pyarrow]")[0]
+
+        base_type = string[:-9]  # get rid of "[pyarrow]"
         try:
             pa_dtype = pa.type_for_alias(base_type)
         except ValueError as err:

pandas/tests/extension/test_arrow.py

@@ -1267,6 +1267,17 @@ def test_arrowdtype_construct_from_string_type_with_unsupported_parameters():
         ArrowDtype.construct_from_string("decimal(7, 2)[pyarrow]")
 
 
+def test_arrowdtype_construct_from_string_type_only_one_pyarrow():
+    # GH#51225
+    invalid = "int64[pyarrow]foobar[pyarrow]"
+    msg = (
+        r"Passing pyarrow type specific parameters \(\[pyarrow\]\) in the "
+        r"string is not supported\."
+    )
+    with pytest.raises(NotImplementedError, match=msg):
+        pd.Series(range(3), dtype=invalid)
+
+
 @pytest.mark.parametrize(
     "interpolation", ["linear", "lower", "higher", "nearest", "midpoint"]
 )