Display form errors using custom validity messages

app/controllers/application_controller.rb

@@ -55,9 +55,9 @@ class ApplicationController < ActionController::Base
 
   private
 
-  def render_no_content(record)
-    helpers.render_errors(record)
-    render html: nil, layout: true
+  def render_errors(record)
+    target = record.new_record? ? [:new, record.parent || record.class] : [:edit, record]
+    render 'errors', assigns: {record: record, target: target}
   end
 
   def rescue_turbo(exception)

app/controllers/quantities_controller.rb

@@ -43,12 +43,15 @@ class QuantitiesController < ApplicationController
     permitted = params.require(:quantity).permit(:parent_id)
     @previous_ancestors = @quantity.ancestors
 
-    # Until UI blocks all disallowed reparents, render error messages if present
-    render_no_content(@quantity) unless @quantity.update(permitted)
-
-    @ancestors = @quantity.ancestors
-    @self_and_progenies = @quantity.with_progenies
-    @before = @self_and_progenies.last.successive
+    if @quantity.update(permitted)
+      @ancestors = @quantity.ancestors
+      @self_and_progenies = @quantity.with_progenies
+      @before = @self_and_progenies.last.successive
+    else
+      # Until UI blocks all disallowed reparents, render error messages if present.
+      flash.now.alert = @quantity.errors.full_messages
+      render :nothing
+    end
   end
 
   def destroy

app/controllers/units_controller.rb

@@ -22,7 +22,7 @@ class UnitsController < ApplicationController
       @before = @unit.successive
       flash.now[:notice] = t('.success', unit: @unit)
     else
-      render :new
+      render_errors @unit
     end
   end
 
@@ -33,7 +33,7 @@ class UnitsController < ApplicationController
     if @unit.update(params.except(:base_id).expect(Unit::ATTRIBUTES))
       flash.now[:notice] = t('.success', unit: @unit)
     else
-      render :edit
+      render_errors @unit
     end
   end