[r] Write group-level string metadata as TILEDB_STRING_UTF8 (#3469)

* [r] Write group-level string metadata as `TILEDB_STRING_UTF8`
String group-level metadata was previously encoded using
`TILEDB_CHAR` or `TILEDB_STRING_ASCII`; however, this resulting in the
metadata being read in as `bytes` in the Python API instead of as `str`.
The Python API already [encodes all strings (`str`) as
`TILEDB_STRING_UTF8`](https://github.com/single-cell-data/TileDB-SOMA/blob/884342a1ceb994d677c52c74ba2d789fc4e208d4/apis/python/src/tiledbsoma/common.cc#L211-L223)
so this PR brings the R API in-line with the Python API

[SC-61001](https://app.shortcut.com/tiledb-inc/story/61001)

resolves #2698

* Add tests

* Update test

* Attempt to fix Python nonsense

* Fix more Python nonsense

* Use spaces instead of tabs

* Update changelog
Bump develop version

apis/r/DESCRIPTION

@@ -6,7 +6,7 @@ Description: Interface for working with 'TileDB'-based Stack of Matrices,
     like those commonly used for single cell data analysis. It is documented at
     <https://github.com/single-cell-data>; a formal specification available is at
     <https://github.com/single-cell-data/SOMA/blob/main/abstract_specification.md>.
-Version: 1.16.99
+Version: 1.16.99.1
 Authors@R: c(
     person(given = "Aaron", family = "Wolen",
            role = c("cre", "aut"), email = "[email protected]",

apis/r/NEWS.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+* Encode string metadata as `TILEDB_STRING_UTF8` instead of `TILEDB_STRING_ASCII`
+
 # tiledbsoma 1.15.0
 
 ## Changes

apis/r/src/groups.cpp

@@ -254,8 +254,9 @@ void c_group_put_metadata(
             std::string s(v[0]);
             // We use TILEDB_CHAR interchangeably with TILEDB_STRING_ASCII is
             // this best string type?
+            // Use TILEDB_STRING_UTF8 for compatibility with Python API
             xp->grpptr->set_metadata(
-                key, TILEDB_STRING_ASCII, s.length(), s.c_str());
+                key, TILEDB_STRING_UTF8, s.length(), s.c_str());
             break;
         }
         case LGLSXP: {  // experimental: map R logical (ie TRUE, FALSE, NA) to

apis/system/tests/test_character_write_python_read_r.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+import pytest
+
+import tiledbsoma
+
+from .common import TestWritePythonReadR
+
+
+class TestCharacterMetadataWritePythonReadR(TestWritePythonReadR):
+
+    @pytest.fixture(scope="class")
+    def experiment(self):
+        exp = tiledbsoma.Experiment.create(self.uri)
+        exp.close
+
+    def base_R_script(self):
+        return f"""
+        library(tiledbsoma)
+
+        exp <- SOMAExperimentOpen("{self.uri}")
+        md <- exp$get_metadata()
+        """
+
+    def test_r_character(self, experiment):
+        self.r_assert(
+            "stopifnot(all(vapply(md, \(x) is.character(x$name), logical(1L))))"
+        )

apis/system/tests/test_character_write_r_read_python.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+
+import pytest
+
+import tiledbsoma
+
+from .common import TestReadPythonWriteR
+
+
+class TestCharacterMetadataWriteRReadPython(TestReadPythonWriteR):
+    @pytest.fixture(scope="class")
+    def R_character(self):
+        base_script = f"""
+        library(tiledbsoma)
+
+        exp <- SOMAExperimentCreate("{self.uri}")
+        exp$close()
+        """
+        self.execute_R_script(base_script)
+
+    def test_py_character(self, R_character):
+        with tiledbsoma.open(self.uri) as exp:
+            for key in exp.metadata.keys():
+                assert isinstance(exp.metadata.get(key), str)