From dfa5d064ddbb9e94323dbb66d8575168bf5ef75f Mon Sep 17 00:00:00 2001
From: Jim Pivarski <jpivarski@gmail.com>
Date: Tue, 15 Aug 2023 16:36:19 -0500
Subject: [PATCH] Allow old pyarrow to forget that an unnullable string has
 unnullable outputs.

---
 src/awkward/operations/str/__init__.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/awkward/operations/str/__init__.py b/src/awkward/operations/str/__init__.py
index a9a14e4dea..199d166d7e 100644
--- a/src/awkward/operations/str/__init__.py
+++ b/src/awkward/operations/str/__init__.py
@@ -119,6 +119,9 @@ def action(layout, **absorb):
                     ),
                     highlevel=False,
                 )
+
+                if out.is_option:
+                    out = out.content
                 if out.is_list and out.parameter("__array__") == "string":
                     out = out.copy(
                         content=out.content.copy(parameters={"__array__": "byte"}),
@@ -140,6 +143,9 @@ def action(layout, **absorb):
 def _erase_list_option(layout):
     from awkward.contents.unmaskedarray import UnmaskedArray
 
+    if layout.is_option:
+        layout = layout.content
+
     assert layout.is_list
     if layout.content.is_option:
         assert isinstance(layout.content, UnmaskedArray)