writeRaster(..., filetype="VRT") crashes R

[brownag]

I stumbled across this case when working on #1714. Setting filetype="VRT" with writeRaster() crashes R.

library(terra)
x <- rast(system.file("ex", "elev.tif", package = "terra"))
writeRaster(x, filename = "foo.vrt", filetype = "VRT")

Note it does write a "foo.vrt" file without the source information we get with vrt(x, filename = "foo2.vrt")

So, after crash in a new session we get:

terra::rast("foo.vrt")
#> class       : SpatRaster 
#> dimensions  : 90, 95, 1  (nrow, ncol, nlyr)
#> resolution  : 0.008333333, 0.008333333  (x, y)
#> extent      : 5.741667, 6.533333, 49.44167, 50.19167  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#> source      : foo.vrt 
#> name        : elevation 
#> min value   :         0 
#> max value   :         0 

---

I figure writeRaster(..., filetype="VRT") is not something folks often try to do, but to avoid a crash the specific value of filetype="VRT" could have an error message that directs the user to to vrt(), or, alternately, passes terra::sources(x) to vrt() and errors for x that exists only in memory.

[rhijmans]

Thank you, I now get

writeRaster(x, filename = "foo.vrt", filetype = "VRT")
#Error: [writeRaster] Cannot directly write to VRT (see '?vrt')

This error will also occur when writeStart is called from other methods that write raster files.