DEV: Validate default value for type: objects theme settings (#25833)

Why this change?

This change adds validation for the default value for `type: objects` theme
settings when a setting theme field is uploaded. This helps the theme
author to ensure that the objects which they specifc in the default
value adhere to the schema which they have declared.

When an error is encountered in one of the objects, the error
message will look something like:

`"The property at JSON Pointer '/0/title' must be at least 5 characters
long."`

We use a JSON Pointer to reference the property in the object which is
something most json-schema validator uses as well.

What does this change do?

1. This commit once again changes the shape of hash returned by
   `ThemeSettingsObjectValidator.validate`. Instead of using the
   property name as the key previously, we have decided to avoid
   multiple levels of nesting and instead use a JSON Pointer as the key
   which helps to simplify the implementation.

2 Introduces `ThemeSettingsObjectValidator.validate_objects` which
  returns an array of validation error messages for all the objects
  passed to the method.

lib/theme_settings_object_validator.rb

@@ -1,37 +1,72 @@
 # frozen_string_literal: true
 
 class ThemeSettingsObjectValidator
+  class << self
+    def validate_objects(schema:, objects:)
+      error_messages = []
+
+      objects.each_with_index do |object, index|
+        humanize_error_messages(
+          self.new(schema: schema, object: object).validate,
+          index:,
+          error_messages:,
+        )
+      end
+
+      error_messages
+    end
+
+    private
+
+    def humanize_error_messages(errors, index:, error_messages:)
+      errors.each do |property_json_pointer, error_details|
+        error_messages.push(*error_details.humanize_messages("/#{index}#{property_json_pointer}"))
+      end
+    end
+  end
+
   class ThemeSettingsObjectErrors
     def initialize
       @errors = []
     end
 
-    def add_error(key, i18n_opts = {})
-      @errors << ThemeSettingsObjectError.new(key, i18n_opts)
+    def add_error(error, i18n_opts = {})
+      @errors << ThemeSettingsObjectError.new(error, i18n_opts)
+    end
+
+    def humanize_messages(property_json_pointer)
+      @errors.map { |error| error.humanize_messages(property_json_pointer) }
     end
 
     def full_messages
       @errors.map(&:error_message)
     end
   end
-
   class ThemeSettingsObjectError
-    def initialize(key, i18n_opts = {})
-      @key = key
+    def initialize(error, i18n_opts = {})
+      @error = error
       @i18n_opts = i18n_opts
     end
 
+    def humanize_messages(property_json_pointer)
+      I18n.t(
+        "themes.settings_errors.objects.humanize_#{@error}",
+        @i18n_opts.merge(property_json_pointer:),
+      )
+    end
+
     def error_message
-      I18n.t("themes.settings_errors.objects.#{@key}", @i18n_opts)
+      I18n.t("themes.settings_errors.objects.#{@error}", @i18n_opts)
     end
   end
 
-  def initialize(schema:, object:, valid_category_ids: nil)
+  def initialize(schema:, object:, valid_category_ids: nil, json_pointer_prefix: "", errors: {})
     @object = object
     @schema_name = schema[:name]
     @properties = schema[:properties]
-    @errors = {}
+    @errors = errors
     @valid_category_ids = valid_category_ids
+    @json_pointer_prefix = json_pointer_prefix
   end
 
   def validate
@@ -39,15 +74,17 @@ class ThemeSettingsObjectValidator
 
     @properties.each do |property_name, property_attributes|
       if property_attributes[:type] == "objects"
-        @object[property_name]&.each do |child_object|
-          @errors[property_name] ||= []
-
-          @errors[property_name].push(
-            self
-              .class
-              .new(schema: property_attributes[:schema], object: child_object, valid_category_ids:)
-              .validate,
-          )
+        @object[property_name]&.each_with_index do |child_object, index|
+          self
+            .class
+            .new(
+              schema: property_attributes[:schema],
+              object: child_object,
+              valid_category_ids:,
+              json_pointer_prefix: "#{@json_pointer_prefix}#{property_name}/#{index}/",
+              errors: @errors,
+            )
+            .validate
         end
       end
     end
@@ -148,8 +185,13 @@ class ThemeSettingsObjectValidator
   end
 
   def add_error(property_name, key, i18n_opts = {})
-    @errors[property_name] ||= ThemeSettingsObjectErrors.new
-    @errors[property_name].add_error(key, i18n_opts)
+    pointer = json_pointer(property_name)
+    @errors[pointer] ||= ThemeSettingsObjectErrors.new
+    @errors[pointer].add_error(key, i18n_opts)
+  end
+
+  def json_pointer(property_name)
+    "/#{@json_pointer_prefix}#{property_name}"
   end
 
   def valid_category_ids

lib/theme_settings_validator.rb

@@ -51,6 +51,10 @@ class ThemeSettingsValidator
           errors:,
           translation_prefix: "string",
         )
+      when types[:objects]
+        errors.push(
+          ThemeSettingsObjectValidator.validate_objects(schema: opts[:schema], objects: value),
+        )
       end
 
       errors