paleolimbot commented on code in PR #12817:
URL: https://github.com/apache/arrow/pull/12817#discussion_r855205407
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r/src/arrow_types.h:
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@@ -100,6 +127,35 @@ std::shared_ptr<arrow::DataType> InferArrowType(SEXP x);
std::shared_ptr<arrow::Array> vec_to_arrow__reuse_memory(SEXP x);
bool can_reuse_memory(SEXP x, const std::shared_ptr<arrow::DataType>& type);
+// These are the types of objects whose conversion to Arrow Arrays is handled
+// entirely in C++. Other types of objects are converted using the
+// infer_type() S3 generic and the as_arrow_array() S3 generic.
+// For data.frame, we need to recurse because the internal conversion
+// can't accomodate calling into R. If the user specifies a target type
+// and that target type is an ExtensionType, we also can't convert
+// natively (but we check for this separately when it applies).
+static inline bool can_convert_native(SEXP x) {
+ if (!Rf_isObject(x)) {
Review Comment:
Anything with a `class()` attribute (although my understanding is that
internally R maintains an "object" bitflag when setting/removing the class
attribute, so this test is fast):
``` r
cpp11::cpp_function("bool is_object(sexp obj) { return Rf_isObject(obj); }")
is_object(1)
#> [1] FALSE
is_object(structure(1, class = "something"))
#> [1] TRUE
```
There might be a type that we haven't considered here (complex maybe?), but
for the most part we had already implemented conversions for all the base R
types.
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