fix bug in st_interpolate_aw()

Author: edzer

NEWS.md

@@ -1,5 +1,7 @@
 # version 1.0-20
 
+* `st_interpolate_aw()` fixes bug when a GEOMETRYCOLLECTION contains multiple POLYGON structures; found by @mtennekes
+
 * `st_buffer()` for geodetic coordinates allows `max_dist` and `min_level` 
    to be specified by feature; #2488 and https://github.com/r-spatial/s2/pull/264
 

R/aggregate.R

@@ -133,7 +133,8 @@ st_interpolate_aw.sf = function(x, to, extensive, ..., keep_NA = FALSE, na.rm =
 
 	# https://stackoverflow.com/questions/57767022/how-do-you-use-st-interpolate-aw-with-polygon-layers-that-legitimately-include-p
 	gc = which(st_is(i, "GEOMETRYCOLLECTION"))
-	i[gc] = st_collection_extract(i[gc], "POLYGON")
+	# i[gc] = st_collection_extract(i[gc], "POLYGON") ## breaks if there are several POLYGONs in a GC
+	i[gc] = do.call(c, lapply(i[gc], function(x) st_sfc(st_union(st_collection_extract(x, "POLYGON")))))
 	two_d = which(st_dimension(i) == 2)
 	i[two_d] = st_cast(i[two_d], "MULTIPOLYGON")