Re-introduce Base#format and Collection#format to fix Rails 7.1 tests

Author: camertron

lib/view_component/base.rb

@@ -316,6 +316,12 @@ def view_cache_dependencies
       []
     end
 
+    # Rails expects us to define `format` on all renderables,
+    # but we do not know the `format` of a ViewComponent until runtime.
+    def format
+      nil
+    end
+
     # The current request. Use sparingly as doing so introduces coupling that
     # inhibits encapsulation & reuse, often making testing difficult.
     #

lib/view_component/collection.rb

@@ -19,6 +19,12 @@ def each(&block)
       components.each(&block)
     end
 
+    # Rails expects us to define `format` on all renderables,
+    # but we do not know the `format` of a ViewComponent until runtime.
+    def format
+      nil
+    end
+
     private
 
     def components