build: error on partially built package group

Author: AladW

lib/pacman/aur-build

@@ -387,16 +387,21 @@ while IFS= read "${read_args[@]}" -ru "$fd" path; do
             printf '%q\n' >&2 "${exists[@]}"
             create_package=0
 
+            if [[ -v results_file ]]; then
+                printf "exist:file://%s\n" "${exists[@]}" | tee -a "$results_file" >/dev/null
+            fi
+
         elif (( ${#exists[@]} )); then
             # Since `makepkg` does not allow building split packages
-            # individually, we restart the build when part of the
+            # individually, we require a new build when part of the
             # package group is unavailable (including -debug packages)
-            printf >&2 '%s: warning: package group partially built\n' "$argv0"
+            printf >&2 '%s: error: package group partially built\n' "$argv0"
             printf '%q\n' >&2 "${exists[@]}"
-        fi
 
-        if (( ${#exists[@]} )) && [[ -v results_file ]]; then
-            printf "exist:file://%s\n" "${exists[@]}" | tee -a "$results_file" >/dev/null
+            # Rebuilding the package group at this stage may result in
+            # checksum errors, if part of the package group is
+            # available in pacman's cache, so we exit with an error.
+            exit 2
         fi
     fi