sf_subset_script.R

if(!requireNamespace("devtools")) install.packages("devtools")
if(!requireNamespace("osmplotr")) install.packages("osmplotr")

dir.create("sfsubsettest/R", recursive=TRUE)
setwd("sfsubsettest")

cat("Package: sfsubsettest
Title: Check sf Subset
Version: 0.0.1
Author: Berry Boessenkool
Maintainer: Berry Boessenkool <berry-b@gmx.de>
License: GPL-2
Description: Check sf Subset.
Imports: osmplotr\n",                            file="DESCRIPTION")

cat(paste("#' dummy function\n#' @param map map\n#' @param obj obj",
"#' @importFrom osmplotr add_osm_objects\n#' @export",
"dummy <- function(map,obj)\n{",
"  add_osm_objects(map, obj[1:10,], col='green')\n}", sep="\n"), 
file="R/dummy.R")

devtools::document()
devtools::install()
library(sfsubsettest)

library(osmplotr)
bbox <- get_bbox(c(12.5, 53.1, 12.6, 53.2))
dat_F <- extract_osm_objects(key="landuse", bbox=bbox, quiet=TRUE, value="forest")
map <- osm_basemap(bbox=bbox, bg='gray95')
map <- dummy(map, dat_F) # class(obj$geometry) problem

class(dat_F$geometry)        # sfc
class(dat_F[1:10,]$geometry) # list

# now change   "["   to   sf:::"[.sf"
cat(paste("#' dummy function\n#' @param map map\n#' @param obj obj",
"#' @importFrom osmplotr add_osm_objects\n#' @export",
"dummy <- function(map,obj)\n{",
"  add_osm_objects(map, sf:::'[.sf'(obj, 1:10, 1:ncol(obj)), col='green')\n}", sep="\n"), 
file="R/dummy.R")
devtools::document()
devtools::install()
library(sfsubsettest)

map <- dummy(map, dat_F) # now works fine
map


remove.packages("sfsubsettest")
setwd("..")
unlink("sfsubsettest", recursive=TRUE)

See comment here - this will always fail without sf being explicitly loaded because (1) osmplotr does not, nor will, depend on sf, that's an uneccessarily "heavy" dependency; and (2) sub-setting is arguably an sf operation that lies beyond the remit of osmplotr, and so it is fair to expect sf to be loaded for that operation. There is unfortunately no place within osmplotr at which a suitably useful message might be issued regarding the necessity of loading sf for such operations, because the objects returned by extract_osm_objects() are intended to be indistinguishable from any sf objects generated with that package.