Add "eselect java-vm update"

Bug: https://bugs.gentoo.org/853928
Signed-off-by: Florian Schmaus <flow@gentoo.org>

2 files changed, 58 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 6c331a2..d8ea978 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,6 @@
+NEXT:
+    * Add "eselect java-vm update" (#853928)
+
 0.4.3:
     * install jpackage symlink
 
diff --git a/src/modules/java-vm.eselect.in b/src/modules/java-vm.eselect.in
index e332c5a..c7d5a82 100644
--- a/src/modules/java-vm.eselect.in
+++ b/src/modules/java-vm.eselect.in
@@ -177,3 +177,58 @@ set_symlink() {
 		die -q "Target \"${1}\" doesn't appear to be valid!"
 	fi
 }
+
+describe_update() {
+	echo "Automatically update the Java system VM"
+}
+
+do_update() {
+	local targets
+	targets=( $(find_targets) )
+
+	if [[ ${#targets[@]} -eq 0 ]]; then
+		echo "No installed Java VMs found, can not update"
+		return
+	fi
+
+	if [[ -e "${VM_SYSTEM}" ]]; then
+		local current_system_vm_name=$(sym_to_vm "${VM_SYSTEM}")
+		echo "Current Java system VM ${current_system_vm_name} is valid, no need to update"
+		return
+	fi
+
+	local new_target old_system_vm_name
+	if [[ -L "${VM_SYSTEM}" ]]; then
+		# There exists a Java system VM symlink that has become stale,
+		# try to find another available VM with the same slot.
+		old_system_vm_name=$(sym_to_vm "${VM_SYSTEM}")
+
+		local old_system_vm_slot="${old_system_vm_name##*-}"
+
+		local target
+		for target in "${targets[@]}"; do
+			local target_slot="${target##*-}"
+			if [[ ${target_slot} -eq ${old_system_vm_slot} ]]; then
+				new_target="${target}"
+				break
+			fi
+		done
+	fi
+
+	if [[ -z "${new_target}" ]]; then
+		# There is no Java system VM symlink or we could not find a
+		# slot-matching replacement. But there are potential targets,
+		# simply choose the first.
+		# TODO: We could get more sophisticated here to select the "best"
+		# target, but that is far from trivial.
+		new_target="${targets[0]}"
+	fi
+
+	local from_vm_text=""
+	if [[ -n "${old_system_vm_name}" ]]; then
+		from_vm_text="from ${old_system_vm_name} "
+	fi
+
+	echo "Updating Java system VM ${from_vm_text}to ${new_target}"
+	set_symlink "${new_target}" "${VM_SYSTEM}"
+}