stub extension type implementation

r/NAMESPACE

@@ -32,10 +32,12 @@ S3method(as_nanoarrow_array,factor)
 S3method(as_nanoarrow_array,nanoarrow_array)
 S3method(as_nanoarrow_array,nanoarrow_buffer)
 S3method(as_nanoarrow_array,vctrs_unspecified)
+S3method(as_nanoarrow_array_extension,default)
 S3method(as_nanoarrow_array_stream,RecordBatchReader)
 S3method(as_nanoarrow_array_stream,data.frame)
 S3method(as_nanoarrow_array_stream,default)
 S3method(as_nanoarrow_array_stream,nanoarrow_array_stream)
+S3method(as_nanoarrow_array_stream_extension,default)
 S3method(as_nanoarrow_buffer,default)
 S3method(as_nanoarrow_buffer,nanoarrow_buffer)
 S3method(as_nanoarrow_schema,DataType)
@@ -46,10 +48,12 @@ S3method(convert_array,default)
 S3method(convert_array,double)
 S3method(convert_array,factor)
 S3method(convert_array,vctrs_partial_frame)
+S3method(convert_array_extension,default)
 S3method(format,nanoarrow_array)
 S3method(format,nanoarrow_array_stream)
 S3method(format,nanoarrow_buffer)
 S3method(format,nanoarrow_schema)
+S3method(infer_nanoarrow_ptype_extension,default)
 S3method(infer_nanoarrow_schema,Array)
 S3method(infer_nanoarrow_schema,ArrowTabular)
 S3method(infer_nanoarrow_schema,ChunkedArray)
@@ -94,15 +98,19 @@ S3method(str,nanoarrow_buffer)
 S3method(str,nanoarrow_schema)
 export(array_stream_set_finalizer)
 export(as_nanoarrow_array)
+export(as_nanoarrow_array_extension)
 export(as_nanoarrow_array_stream)
+export(as_nanoarrow_array_stream_extension)
 export(as_nanoarrow_buffer)
 export(as_nanoarrow_schema)
 export(basic_array_stream)
 export(collect_array_stream)
 export(convert_array)
+export(convert_array_extension)
 export(convert_array_stream)
 export(convert_buffer)
 export(infer_nanoarrow_ptype)
+export(infer_nanoarrow_ptype_extension)
 export(infer_nanoarrow_schema)
 export(na_binary)
 export(na_bool)
@@ -151,6 +159,7 @@ export(nanoarrow_array_modify)
 export(nanoarrow_array_set_schema)
 export(nanoarrow_buffer_append)
 export(nanoarrow_buffer_init)
+export(nanoarrow_extension_spec)
 export(nanoarrow_pointer_addr_chr)
 export(nanoarrow_pointer_addr_dbl)
 export(nanoarrow_pointer_addr_pretty)
@@ -162,6 +171,9 @@ export(nanoarrow_pointer_set_protected)
 export(nanoarrow_schema_modify)
 export(nanoarrow_schema_parse)
 export(nanoarrow_version)
+export(register_nanoarrow_extension)
+export(resolve_nanoarrow_extension)
+export(unregister_nanoarrow_extension)
 importFrom(utils,getFromNamespace)
 importFrom(utils,str)
 useDynLib(nanoarrow, .registration = TRUE)

r/R/type-extension.R

@@ -0,0 +1,125 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+#' Register Arrow extension types
+#'
+#' @param extension_name An Arrow extension type name (e.g., arrow.r.vctrs)
+#' @param extension_spec An extension specification inheriting from
+#'   'nanoarrow_extension_spec'.
+#' @param data Optional data to include in the extension type specification
+#' @param subclass A subclass for the extension type specification. Extension
+#'    methods will dispatch on this object.
+#'
+#' @return
+#'   - `nanoarrow_extension_spec()` returns an object of class
+#'     'nanoarrow_extension_spec'.
+#'   - `register_nanoarrow_extension()` returns `extension_spec`, invisibly.
+#'   - `unregister_nanoarrow_extension()` returns `extension_name`, invisibly.
+#'   - `resolve_nanoarrow_extension()` returns an object of class
+#'     'nanoarrow_extension_spec' or NULL if the extension type was not
+#'     registered.
+#' @export
+#'
+#' @examples
+#' nanoarrow_extension_spec("mynamespace.mytype", subclass = "mypackage_mytype_spec")
+nanoarrow_extension_spec <- function(extension_name, data = NULL,
+                                     subclass = character()) {
+  structure(
+    list(extension_name = extension_name, data = data),
+    class = union(subclass, "nanoarrow_extension_spec")
+  )
+}
+
+#' @rdname nanoarrow_extension_spec
+#' @export
+register_nanoarrow_extension <- function(extension_spec) {
+  extension_registry[[extension_spec$extension_name]] <- extension_spec
+  invisible(extension_spec)
+}
+
+#' @rdname nanoarrow_extension_spec
+#' @export
+unregister_nanoarrow_extension <- function(extension_name) {
+  extension_registry[[extension_name]] <- NULL
+  invisible(extension_name)
+}
+
+#' @rdname nanoarrow_extension_spec
+#' @export
+resolve_nanoarrow_extension <- function(extension_name) {
+  extension_registry[[extension_name]]
+}
+
+
+#' Implement Arrow extension types
+#'
+#' @inheritParams nanoarrow_extension_spec
+#' @param x,array,to,schema,... Passed from [infer_nanoarrow_ptype()],
+#'   [convert_array()], [as_nanoarrow_array()], and/or
+#'   [as_nanoarrow_array_stream()].
+#'
+#' @return
+#'   - `infer_nanoarrow_ptype_extension()`: The R vector prototype to be used
+#'     as the default conversion target.
+#'   - `convert_array_extension()`: An R vector of type `to`.
+#'   - `as_nanoarrow_array_extension()`: A [nanoarrow_array][as_nanoarrow_array].
+#' @export
+#'
+infer_nanoarrow_ptype_extension <- function(extension_spec, x) {
+  UseMethod("infer_nanoarrow_ptype_extension")
+}
+
+#' @export
+infer_nanoarrow_ptype_extension.default <- function(extension_spec, x) {
+  stop("not implemented")
+}
+
+#' @rdname infer_nanoarrow_ptype_extension
+#' @export
+convert_array_extension <- function(extension_spec, array, to, ...) {
+  UseMethod("convert_array_extension")
+}
+
+#' @export
+convert_array_extension.default <- function(extension_spec, array, to, ...) {
+  stop_cant_convert_array(array, to)
+}
+
+#' @rdname infer_nanoarrow_ptype_extension
+#' @export
+as_nanoarrow_array_extension <- function(extension_spec, x, ..., schema = NULL) {
+  UseMethod("as_nanoarrow_array_extension")
+}
+
+#' @export
+as_nanoarrow_array_extension.default <- function(extension_spec, x, ..., schema = NULL) {
+  stop("Not implemented")
+}
+
+#' @rdname infer_nanoarrow_ptype_extension
+#' @export
+as_nanoarrow_array_stream_extension <- function(extension_spec, x, ..., schema = NULL) {
+  UseMethod("as_nanoarrow_array_stream_extension")
+}
+
+#' @export
+as_nanoarrow_array_stream_extension.default <- function(extension_spec, x, ..., schema = NULL) {
+  stop("not implemented")
+}
+
+# Mutable registry to look up extension specifications
+extension_registry <- new.env(parent = emptyenv())

r/tests/testthat/test-type-extension.R

@@ -0,0 +1,20 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+test_that("multiplication works", {
+  expect_equal(2 * 2, 4)
+})