Added check to ensure we are in lighttable view prior to callling darktable.register_lib. If darktable was invoked in single image (darkroom) mode, then an event handler is registered to detect the change from darkroom mode to lighttable mode so that we can then call darktable.register_lib.

contrib/rename-tags.lua

@@ -35,6 +35,10 @@ local debug = require "darktable.debug"
 -- check API version
 du.check_min_api_version("3.0.0", "rename-tags") 
 
+local rt = {}
+rt.module_installed = false
+rt.event_registered = false
+
 -- GUI entries
 local old_tag = darktable.new_widget("entry") { tooltip = "Enter old tag" }
 local new_tag = darktable.new_widget("entry") { tooltip = "Enter new tag" }
@@ -99,6 +103,13 @@ local function rename_tags()
   rename_reset()
 end
 
+local function install_module()
+  if not rt.module_installed then
+    darktable.register_lib ("rename_tags", "rename tag", true, true, {[darktable.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_RIGHT_CENTER", 20},}, rt.rename_widget, nil, nil)
+    rt.module_installed = true
+  end
+end
+
 -- GUI
 local old_widget = darktable.new_widget ("box") {
     orientation = "horizontal",
@@ -112,7 +123,7 @@ local new_widget = darktable.new_widget ("box") {
     new_tag
 }
 
-local rename_widget = darktable.new_widget ("box") {
+rt.rename_widget = darktable.new_widget ("box") {
     orientation = "vertical",
     reset_callback = rename_reset,
     old_widget,
@@ -120,6 +131,20 @@ local rename_widget = darktable.new_widget ("box") {
     darktable.new_widget("button") { label = "Go", clicked_callback = rename_tags }
 }
 
+if darktable.gui.current_view().name == "lighttable" then
+  install_module()
+else
+  if not rt.event_registered then
+    darktable.register_event(
+      "view-changed",
+      function(event, old_view, new_view)
+        if new_view.name == "lighttable" and old_view.name == "darkroom" then
+          install_module()
+         end
+      end
+    )
+    rt.event_registered = true
+  end
+end
 
-darktable.register_lib ("rename_tags", "rename tag", true, true, {[darktable.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_RIGHT_CENTER", 20},}, rename_widget, nil, nil)