select_time() with one time returns cubes without end-times, creating errors for st_as_stars() etc

[cboettig]

When we apply gdalcubes::select_time() with a single time value, we get an object that does not have a start and end time. When we then use st_as_stars() to convert this to a stars object, we get an erroneous end time. (Sometimes this is the origin time, 1970-01-01, which is bad, but sometimes I get non-date-times for this, which lead to breaking errors).

We can see this error using a simple modification to the example code for select_time()

# create image collection from example Landsat data only 
# if not already done in other examples
if (!file.exists(file.path(tempdir(), "L8.db"))) {
  L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
                         ".TIF", recursive = TRUE, full.names = TRUE)
  create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db"), quiet = TRUE) 
}

L8.col = image_collection(file.path(tempdir(), "L8.db"))
v = cube_view(extent=list(left=388941.2, right=766552.4, 
                          bottom=4345299, top=4744931, t0="2018-04", t1="2018-07"),
              srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
L8.cube = raster_cube(L8.col, v) 
L8.rgb = select_bands(L8.cube, c("B02", "B03", "B04"))

Now select only one time:

L8.rgb = select_time(L8.rgb, c("2018-04"))
st_as_stars(L8.rgb)

gives us:

Note the erroneous end time (1970-01-01).