have st_layers() return sf_layers,data.frame objects

NEWS.md

@@ -1,5 +1,7 @@
 # version 1.0-17
 
+* `st_layers()` returns an object of class `c("sf_layers", "data.frame")`, with a dedicated `print` method.
+
 * when `dim` is not `XYZM`, `sf_as_sf.data.frame()` interprets a length 4 `coords` argument to specify the corners of a rectangular polygon; #2357
 
 * `st_interpolate_aw()` gains an `na.rm` argument, for removing features with `NA` attributes before interpolating; #830

R/read.R

@@ -700,7 +700,7 @@ st_layers = function(dsn, options = character(0), do_count = FALSE) {
 		Encoding(ret[[1]]) <- "UTF-8"
 		ret[[1]] <- enc2native(ret[[1]])
 	}
-	ret
+	structure(ret, row.names = seq_along(ret[[1]]), class = c("sf_layers", "data.frame"))
 }
 
 guess_driver = function(dsn) {

src/gdal_read.cpp

@@ -182,17 +182,15 @@ Rcpp::List CPL_get_layers(Rcpp::CharacterVector datasource, Rcpp::CharacterVecto
 			feature_count(iLayer) = count_features(poLayer);
 	}
 
-	Rcpp::List out(6);
-	out(0) = names;
-	out(1) = geomtype;
-	out(2) = poDS->GetDriverName();
-	out(3) = feature_count;
-	out(4) = field_count;
-	out(5) = layer_crs;
+	Rcpp::List ret = Rcpp::List::create(
+		Rcpp::_["name"] = names,
+		Rcpp::_["geomtype"] = geomtype,
+		Rcpp::_["driver"] = poDS->GetDriverName(),
+		Rcpp::_["features"] = feature_count,
+		Rcpp::_["fields"] = field_count,
+		Rcpp::_["crs"] = layer_crs);
 	GDALClose(poDS); // close & destroys data source
-	out.attr("names") = Rcpp::CharacterVector::create("name", "geomtype", "driver", "features", "fields", "crs");
-	out.attr("class") = Rcpp::CharacterVector::create("sf_layers");
-	return out;
+	return ret;
 }
 
 Rcpp::List sf_from_ogrlayer(OGRLayer *poLayer, bool quiet, bool int64_as_string,