[C++] Exporting an ExtensionType with BinaryView or StringView storage to C does not export extra buffer sizes array

[paleolimbot]

Describe the bug, including details regarding any error messages, version, and platform.

Discovered by @kylebarron when working on GeoArrow WKB extensions! I started geoarrow/geoarrow-python#72 to fix because I thought it was a geoarrow problem but I think it's an Arrow one. In the debugger,

arrow/cpp/src/arrow/c/bridge.cc

Lines 589 to 590 in 6804059

	bool need_variadic_buffer_sizes =
	data->type->id() == Type::BINARY_VIEW || data->type->id() == Type::STRING_VIEW;

...evaluates to false in the following reprex:

import pyarrow as pa
import geoarrow.pyarrow as ga

wkb_item = b"\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x3e\x40\x00\x00\x00\x00\x00\x00\x24\x40"
array = ga.array([wkb_item], ga.wkb_view())

schema_capsule, array_capsule = array.__arrow_c_array__()
rearr = pa.Array._import_from_c_capsule(schema_capsule, array_capsule)
rearr.validate(full=True)
#> pyarrow.lib.ArrowIndexError: View at slot 0 references buffer 0 but there are only 0 data buffers

Component(s)

C++

[ShubhSingh07]

Hi, I'd like to work on this issue. Could you please assign it to me?

[kou]

There is a PR for this: #46660

You can review it.

[paleolimbot]

Yes, apologies that I had the PR half done by the time I opened the issue 😬 . Feel free to review or ping me to review on a different issue!

[paleolimbot]

Issue resolved by pull request 46660
#46660