Series.str.find fix for pd.ArrowDtype(pa.string()) (pandas-dev#56792)

* fix find

* gh reference

* add test for Nones

* fix min version compat

* restore test

* improve test cases

* fix empty string

* inline

* improve tests

* fix

* Revert "fix"

This reverts commit 7fa21eb.

* fix

* merge

* inline

---------

Co-authored-by: Rohan Jain <rohanjain@microsoft.com>

Author: 2 people

pandas/core/arrays/arrow/array.py

@@ -2364,20 +2364,26 @@ def _str_fullmatch(
         return self._str_match(pat, case, flags, na)
 
     def _str_find(self, sub: str, start: int = 0, end: int | None = None) -> Self:
-        if start != 0 and end is not None:
+        if (start == 0 or start is None) and end is None:
+            result = pc.find_substring(self._pa_array, sub)
+        else:
+            if sub == "":
+                # GH 56792
+                result = self._apply_elementwise(lambda val: val.find(sub, start, end))
+                return type(self)(pa.chunked_array(result))
+            if start is None:
+                start_offset = 0
+                start = 0
+            elif start < 0:
+                start_offset = pc.add(start, pc.utf8_length(self._pa_array))
+                start_offset = pc.if_else(pc.less(start_offset, 0), 0, start_offset)
+            else:
+                start_offset = start
             slices = pc.utf8_slice_codeunits(self._pa_array, start, stop=end)
             result = pc.find_substring(slices, sub)
-            not_found = pc.equal(result, -1)
-            start_offset = max(0, start)
+            found = pc.not_equal(result, pa.scalar(-1, type=result.type))
             offset_result = pc.add(result, start_offset)
-            result = pc.if_else(not_found, result, offset_result)
-        elif start == 0 and end is None:
-            slices = self._pa_array
-            result = pc.find_substring(slices, sub)
-        else:
-            raise NotImplementedError(
-                f"find not implemented with {sub=}, {start=}, {end=}"
-            )
+            result = pc.if_else(found, offset_result, -1)
         return type(self)(result)
 
     def _str_join(self, sep: str) -> Self:

pandas/tests/extension/test_arrow.py

@@ -23,6 +23,7 @@
     BytesIO,
     StringIO,
 )
+from itertools import combinations
 import operator
 import pickle
 import re
@@ -1933,13 +1934,18 @@ def test_str_fullmatch(pat, case, na, exp):
 
 
 @pytest.mark.parametrize(
-    "sub, start, end, exp, exp_typ",
-    [["ab", 0, None, [0, None], pa.int32()], ["bc", 1, 3, [1, None], pa.int64()]],
+    "sub, start, end, exp, exp_type",
+    [
+        ["ab", 0, None, [0, None], pa.int32()],
+        ["bc", 1, 3, [1, None], pa.int64()],
+        ["ab", 1, 3, [-1, None], pa.int64()],
+        ["ab", -3, -3, [-1, None], pa.int64()],
+    ],
 )
-def test_str_find(sub, start, end, exp, exp_typ):
+def test_str_find(sub, start, end, exp, exp_type):
     ser = pd.Series(["abc", None], dtype=ArrowDtype(pa.string()))
     result = ser.str.find(sub, start=start, end=end)
-    expected = pd.Series(exp, dtype=ArrowDtype(exp_typ))
+    expected = pd.Series(exp, dtype=ArrowDtype(exp_type))
     tm.assert_series_equal(result, expected)
 
 
@@ -1951,10 +1957,70 @@ def test_str_find_negative_start():
     tm.assert_series_equal(result, expected)
 
 
-def test_str_find_notimplemented():
+def test_str_find_no_end():
     ser = pd.Series(["abc", None], dtype=ArrowDtype(pa.string()))
-    with pytest.raises(NotImplementedError, match="find not implemented"):
-        ser.str.find("ab", start=1)
+    if pa_version_under13p0:
+        # https://github.com/apache/arrow/issues/36311
+        with pytest.raises(pa.lib.ArrowInvalid, match="Negative buffer resize"):
+            ser.str.find("ab", start=1)
+    else:
+        result = ser.str.find("ab", start=1)
+        expected = pd.Series([-1, None], dtype="int64[pyarrow]")
+        tm.assert_series_equal(result, expected)
+
+
+def test_str_find_negative_start_negative_end():
+    # GH 56791
+    ser = pd.Series(["abcdefg", None], dtype=ArrowDtype(pa.string()))
+    result = ser.str.find(sub="d", start=-6, end=-3)
+    expected = pd.Series([3, None], dtype=ArrowDtype(pa.int64()))
+    tm.assert_series_equal(result, expected)
+
+
+def test_str_find_large_start():
+    # GH 56791
+    ser = pd.Series(["abcdefg", None], dtype=ArrowDtype(pa.string()))
+    if pa_version_under13p0:
+        # https://github.com/apache/arrow/issues/36311
+        with pytest.raises(pa.lib.ArrowInvalid, match="Negative buffer resize"):
+            ser.str.find(sub="d", start=16)
+    else:
+        result = ser.str.find(sub="d", start=16)
+        expected = pd.Series([-1, None], dtype=ArrowDtype(pa.int64()))
+        tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.skipif(
+    pa_version_under13p0, reason="https://github.com/apache/arrow/issues/36311"
+)
+@pytest.mark.parametrize("start", list(range(-15, 15)) + [None])
+@pytest.mark.parametrize("end", list(range(-15, 15)) + [None])
+@pytest.mark.parametrize(
+    "sub",
+    ["abcaadef"[x:y] for x, y in combinations(range(len("abcaadef") + 1), r=2)]
+    + [
+        "",
+        "az",
+        "abce",
+    ],
+)
+def test_str_find_e2e(start, end, sub):
+    s = pd.Series(
+        ["abcaadef", "abc", "abcdeddefgj8292", "ab", "a", ""],
+        dtype=ArrowDtype(pa.string()),
+    )
+    object_series = s.astype(pd.StringDtype())
+    result = s.str.find(sub, start, end)
+    expected = object_series.str.find(sub, start, end).astype(result.dtype)
+    tm.assert_series_equal(result, expected)
+
+
+def test_str_find_negative_start_negative_end_no_match():
+    # GH 56791
+    ser = pd.Series(["abcdefg", None], dtype=ArrowDtype(pa.string()))
+    result = ser.str.find(sub="d", start=-3, end=-6)
+    expected = pd.Series([-1, None], dtype=ArrowDtype(pa.int64()))
+    tm.assert_series_equal(result, expected)
 
 
 @pytest.mark.parametrize(