Enforce SQLite column limits via CHECK constraints

Patch the sqlite adapter to add CHECK constraints for string and text
column limits. We'll do them inline, so that any column changes
automatically update the constraints.

config/initializers/table_definition_column_limits.rb

@@ -8,8 +8,6 @@
 #   - size: :medium: 16,777,215 (MEDIUMTEXT)
 #   - size: :long: 4,294,967,295 (LONGTEXT)
 #
-# This ensures the SQLite schema records the same limits as MySQL,
-# which the ColumnLimits validation concern uses to enforce limits.
 
 module TableDefinitionColumnLimits
   TEXT_SIZE_TO_LIMIT = {
@@ -45,14 +43,28 @@ ActiveSupport.on_load(:active_record) do
   ActiveRecord::ConnectionAdapters::TableDefinition.prepend(TableDefinitionColumnLimits)
 end
 
-ActiveSupport.on_load(:action_text_rich_text) do
-  include ColumnLimits
+# For SQLite: append inline CHECK constraints to enforce string/text length limits.
+# since SQLite doesn't natively enforce VARCHAR/TEXT length limits.
+module SQLiteColumnLimitCheckConstraints
+  def add_column_options!(sql, options)
+    super
+
+    column = options[:column]
+    if column && column.limit && %i[string text].include?(column.type)
+      check_expr = if column.type == :string
+        # VARCHAR limits are in characters
+        %(length("#{column.name}") <= #{column.limit})
+      else
+        # TEXT limits are in bytes
+        %(length(CAST("#{column.name}" AS BLOB)) <= #{column.limit})
+      end
+      sql << " CHECK(#{check_expr})"
+    end
+
+    sql
+  end
 end
 
-ActiveSupport.on_load(:active_storage_blob) do
-  include ColumnLimits
-end
-
-ActiveSupport.on_load(:active_storage_attachment) do
-  include ColumnLimits
+ActiveSupport.on_load(:active_record_sqlite3adapter) do
+  ActiveRecord::ConnectionAdapters::SQLite3::SchemaCreation.prepend(SQLiteColumnLimitCheckConstraints)
 end