Ensure get_fields always returns strings, not symbols, for consistency.

lib/rest_framework/controller_mixins/models.rb

@@ -91,9 +91,10 @@ def get_label(s)
 
     # Get the available fields. Returning `nil` indicates that anything should be accepted. If
     # `fallback` is true, then we should fallback to this controller's model columns, or an empty
-    # array.
+    # array. This should always return an array of strings, no symbols, and possibly `nil` (only if
+    # `fallback` is false).
     def get_fields(input_fields: nil, fallback: true)
-      input_fields ||= self.fields if fallback
+      input_fields ||= self.fields&.map(&:to_s) if fallback
 
       # If fields is a hash, then parse it.
       if input_fields.is_a?(Hash)

lib/rest_framework/filters.rb

@@ -14,14 +14,12 @@ class RESTFramework::ModelFilter < RESTFramework::BaseFilter
   # Get a list of filterset fields for the current action. Fallback to columns because we don't want
   # to try filtering by any query parameter because that could clash with other query parameters.
   def _get_fields
-    return (
-      @controller.class.filterset_fields || @controller.get_fields(fallback: true)
-    ).map(&:to_s)
+    # Always return a list of strings; `@controller.get_fields` already does this.
+    return @controller.class.filterset_fields&.map(&:to_s) || @controller.get_fields(fallback: true)
   end
 
   # Filter params for keys allowed by the current action's filterset_fields/fields config.
   def _get_filter_params
-    # Map filterset fields to strings because query parameter keys are strings.
     fields = self._get_fields
 
     return @controller.request.query_parameters.select { |p, _|
@@ -69,7 +67,7 @@ class RESTFramework::ModelOrderingFilter < RESTFramework::BaseFilter
   # Get a list of ordering fields for the current action. Do not fallback to columns in case the
   # user wants to order by a virtual column.
   def _get_fields
-    return (@controller.class.ordering_fields || @controller.get_fields)&.map(&:to_s)
+    return @controller.class.ordering_fields&.map(&:to_s) || @controller.get_fields
   end
 
   # Convert ordering string to an ordering configuration.
@@ -119,10 +117,10 @@ class RESTFramework::ModelSearchFilter < RESTFramework::BaseFilter
   # common string-like columns by default.
   def _get_fields
     if search_fields = @controller.class.search_fields
-      return search_fields
+      return search_fields&.map(&:to_s)
     end
 
-    columns = @controller.class.get_model.columns_hash.keys
+    columns = @controller.class.get_model.column_names
     return @controller.get_fields(fallback: true).select { |f|
       f.in?(RESTFramework.config.search_columns) && f.in?(columns)
     }

lib/rest_framework/utils.rb

@@ -150,11 +150,13 @@ def self.parse_fields_hash(fields_hash, model, exclude_associations: nil)
       Rails.logger.warn("RRF: Unknown key in fields hash: #{k}")
     end
 
-    return parsed_fields
+    # We should always return strings, not symbols.
+    return parsed_fields.map(&:to_s)
   end
 
   # Get the fields for a given model, including not just columns (which includes
-  # foreign keys), but also associations.
+  # foreign keys), but also associations. Note that we always return an array of
+  # strings, not symbols.
   def self.fields_for(model, exclude_associations: nil)
     foreign_keys = model.reflect_on_all_associations(:belongs_to).map(&:foreign_key)