Only name output bands if it won't error

NEWS.md

@@ -1,5 +1,12 @@
 # rsi (development version)
 
+* `stack_rasters()` will only rename bands if `band_names` is the same length as 
+  the number of bands in the output raster (or missing, or defined by a 
+  function). It will now warn you if these lengths are different. Previously, if 
+  you provided more than the required number of band names, `stack_rasters()` 
+  would silently ignore the extra names, and would error if you provided fewer 
+  names than bands. 
+
 # rsi 0.1.2
 
 * `get_stac_data()` no longer includes `mask_band` in its outputs when 

R/get_stac_data.R

@@ -298,7 +298,11 @@ get_stac_data <- function(aoi,
   if (is.null(names(asset_names))) names(asset_names) <- asset_names
 
   items_urls <- extract_urls(asset_names, items)
-  if (!is.null(mask_band)) items_urls[[mask_band]] <- rstac::assets_url(items, mask_band)
+  drop_mask_band <- FALSE
+  if (!is.null(mask_band) && !(mask_band %in% names(items_urls))) {
+    items_urls[[mask_band]] <- rstac::assets_url(items, mask_band)
+    drop_mask_band <- TRUE
+  }
 
   download_locations <- data.frame(
     matrix(
@@ -376,6 +380,8 @@ get_stac_data <- function(aoi,
     on.exit(file.remove(unlist(download_results[["final_bands"]])), add = TRUE)
   }
 
+  if (drop_mask_band) items_urls[[mask_band]] <- NULL
+
   mapply(
     function(in_bands, vrt) {
       stack_rasters(

R/stack_rasters.R

@@ -180,6 +180,8 @@ stack_rasters <- function(rasters,
   if (!missing(band_names) && is.function(band_names)) {
     var_names <- band_names(var_names)
   }
+  # technically we could have skipped reading the names of each raster here
+  # and just accepted the band names, but we want to check the CRS anyway
   if (!missing(band_names) && is.character(band_names)) {
     var_names <- band_names
   }
@@ -233,16 +235,32 @@ stack_rasters <- function(rasters,
 
   band_no <- 1
   vrt_bands <- vector("list", length(intermediate_vrt))
+
+  set_names <- FALSE
+  if (length(intermediate_vrt) == length(var_names)) {
+    set_names <- TRUE
+  } else if (!missing(band_names)) {
+    rlang::warn(
+      c(
+        "The number of band names provided did not match the number of bands in the output file.",
+        i = "Ignoring the provided band names and using default values instead."
+      ),
+      class = "rsi_band_name_length_mismatch"
+    )
+  }
+
   for (vrt in intermediate_vrt) {
     vrt <- readLines(vrt)
     band_def <- grep("VRTRasterBand", vrt)
     vrt <- vrt[seq(band_def[[1]], band_def[[2]])]
     vrt[1] <- gsub("band=\"1\"", paste0("band=\"", band_no, "\""), vrt[1])
-    vrt <- c(
-      vrt[1],
-      paste0("    <Description>", var_names[[band_no]], "</Description>"),
-      vrt[2:length(vrt)]
-    )
+    if (set_names) {
+      vrt <- c(
+        vrt[1],
+        paste0("    <Description>", var_names[[band_no]], "</Description>"),
+        vrt[2:length(vrt)]
+      )
+    }
 
     vrt_bands[[band_no]] <- vrt
 

tests/testthat/test-stack_rasters.R

@@ -143,3 +143,23 @@ test_that("type_and_length checks", {
     error = TRUE
   )
 })
+
+test_that("stack_rasters warns when band names aren't the right length", {
+  expect_warning(
+    stack_rasters(
+      list(system.file("rasters/example_sentinel1.tif", package = "rsi")),
+      tempfile(fileext = ".vrt"),
+      band_names = "VH"
+    ),
+    class = "rsi_band_name_length_mismatch"
+  )
+
+  expect_warning(
+    stack_rasters(
+      list(system.file("rasters/example_sentinel1.tif", package = "rsi")),
+      tempfile(fileext = ".vrt"),
+      band_names = c("VH", "VV", "EXTRA")
+    ),
+    class = "rsi_band_name_length_mismatch"
+  )
+})