[GitHub] [arrow] romainfrancois commented on a change in pull request #7514: ARROW-6235: [R] Implement conversion from arrow::BinaryArray to R character vector

[GitBox]

romainfrancois commented on a change in pull request #7514:
URL: https://github.com/apache/arrow/pull/7514#discussion_r446041588



##########
File path: r/src/array_from_vector.cpp
##########
@@ -1067,12 +1110,22 @@ std::shared_ptr<arrow::DataType> 
InferArrowTypeFromVector<VECSXP>(SEXP x) {
   if (Rf_inherits(x, "data.frame")) {
     return InferArrowTypeFromDataFrame(x);
   } else {
-    if (XLENGTH(x) == 0) {
-      Rcpp::stop(
-          "Requires at least one element to infer the values' type of a list 
vector");
-    }
+    SEXP ptype = Rf_getAttrib(x, symbols::ptype);
+    if (ptype == R_NilValue) {
+      if (XLENGTH(x) == 0) {
+        Rcpp::stop(
+            "Requires at least one element to infer the values' type of a list 
vector");
+      }
 
-    return arrow::list(InferArrowType(VECTOR_ELT(x, 0)));
+      return arrow::list(InferArrowType(VECTOR_ELT(x, 0)));
+    } else {
+      // special case list(raw()) -> BinaryArray
+      if (TYPEOF(ptype) == RAWSXP) {
+        return arrow::binary();
+      }
+
+      return arrow::list(InferArrowType(ptype));

Review comment:
       Done. I had to modify the roundtrip checks to use `expect_equivalent()` 
because a roundtrip might add information: 
   
   ```
   list() -> List Array -> list_of( ptype = <from list array value type>) 
   ```
   




----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
us...@infra.apache.org