Refuse windowed and subset in coregister

Author: mzarowka

NEWS.md

@@ -1,5 +1,7 @@
 # HSItools (development version)
 
+-   `hsi_coregister()` now errors when `x` is a window, layer subset or combination of files. It warps the file on disk, so these inputs previously produced silently misregistered output.
+
 -   `hsi_coregister()` now returns a readable raster; previously the returned object pointed at a deleted temporary file. It also warps directly to `filename` without an intermediate copy.
 
 # HSItools 0.5.3

R/hsi_coregister.R

@@ -2,8 +2,8 @@
 #'
 #' @family HSI Co-registration
 #'
-#' @param x A [`SpatRaster`][terra::SpatRaster-class] to warp. Must have a
-#'   file source on disk.
+#' @param x A [`SpatRaster`][terra::SpatRaster-class] to warp. Must be a
+#'   whole file on disk, not a window, layer subset or combination of files.
 #' @param y A [`SpatRaster`][terra::SpatRaster-class] defining the output grid.
 #'   Output extent, resolution, and dimensions are taken from this raster.
 #' @param gcp A [data.frame] or [tibble][tibble::tibble] of matched GCPs from
@@ -129,6 +129,26 @@ hsi_coregister <- function(
     )
   }
 
+  # Source must be the whole file: GDAL warps the file, not a view of it
+  x_sources <- terra::sources(x, bands = TRUE)
+
+  x_file <- terra::rast(source_path)
+
+  is_whole_file <- length(unique(x_sources$source)) == 1 &&
+    identical(as.integer(x_sources$bands), seq_len(terra::nlyr(x_file))) &&
+    identical(as.vector(terra::ext(x)), as.vector(terra::ext(x_file)))
+
+  if (!is_whole_file) {
+    cli::cli_abort(
+      c(
+        "{.arg x} is not a whole file on disk.",
+        "i" = "Windows, layer subsets and combined rasters cannot be warped.",
+        "i" = "Write it to disk first with {.code terra::writeRaster()}."
+      ),
+      class = "hsitools_error"
+    )
+  }
+
   # Temp VRT for GCP embedding
   vrt_path <- withr::local_tempfile(fileext = ".vrt")
 

man/hsi_coregister.Rd

@@ -232,6 +232,29 @@ test_that("hsi_coregister errors when x has no file source", {
   )
 })
 
+test_that("hsi_coregister errors when x is a window or layer subset of its file", {
+  # Views of the file on disk, derived from copies so the fixture is untouched
+  windowed <- terra::subset(
+    test_reflectance,
+    seq_len(terra::nlyr(test_reflectance))
+  )
+  terra::window(windowed) <- terra::ext(test_reflectance) -
+    terra::res(test_reflectance)
+
+  layer_subset <- terra::subset(test_reflectance, 1:3)
+
+  expect_error(
+    hsi_coregister(windowed, test_target, test_gcp),
+    "not a whole file",
+    class = "hsitools_error"
+  )
+  expect_error(
+    hsi_coregister(layer_subset, test_target, test_gcp),
+    "not a whole file",
+    class = "hsitools_error"
+  )
+})
+
 test_that("hsi_coregister errors with invalid method", {
   expect_error(
     hsi_coregister(test_reflectance, test_target, test_gcp, method = "invalid"),