romainfrancois commented on pull request #7660:
URL: https://github.com/apache/arrow/pull/7660#issuecomment-654949268
I think we need a function for the `raws <- vctrs::new_list_of(...)` part,
and probably an equivalent function for the other binary types, but `binary()`,
`large_binary()` and `fixed_size_binary()` which would be the obvious choice is
already taken.
I think that in this function:
```
template <>
std::shared_ptr<arrow::DataType> InferArrowTypeFromVector<VECSXP>(SEXP x) {
if (Rf_inherits(x, "data.frame") || Rf_inherits(x, "POSIXlt")) {
return InferArrowTypeFromDataFrame(x);
} else {
if (Rf_inherits(x, "arrow_fixed_size_binary")) {
SEXP byte_width = Rf_getAttrib(x, symbols::byte_width);
if (Rf_isNull(byte_width) || TYPEOF(byte_width) != INTSXP ||
XLENGTH(byte_width) != 1) {
Rcpp::stop("malformed arrow_fixed_size_binary object");
}
return arrow::fixed_size_binary(INTEGER(byte_width)[0]);
}
SEXP ptype = Rf_getAttrib(x, symbols::ptype);
if (Rf_isNull(ptype)) {
if (XLENGTH(x) == 0) {
Rcpp::stop(
"Requires at least one element to infer the values' type of a
list vector");
}
ptype = VECTOR_ELT(x, 0);
}
// special case list(raw()) -> BinaryArray
if (TYPEOF(ptype) == RAWSXP) {
return arrow::binary();
}
return arrow::list(InferArrowType(ptype));
}
}
```
we should rather dispatch based on an r type for binary and large binary, as
it's done here for fixed size binary, and forget the magic conversion of a
`vctrs_list_of<raw>` to a `BinaryArray`, as we might actually want to create an
Array of type `List<uint8>`:
``` r
arrow::list_of(arrow::uint8())
#> ListType
#> list<item: uint8>
```
<sup>Created on 2020-07-07 by the [reprex
package](https://reprex.tidyverse.org) (v0.3.0.9001)</sup>
but type deduction currently short circuits it.
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