Add ignore_empty_cache option for saving memory

Author: w-masahiro-ct

README.md

@@ -189,6 +189,8 @@ The `tailwind_merge` config is an object with several keys:
 tailwind_merge_config = {
   # ↓ *Optional* Define how many values should be stored in cache.
   cache_size: 500,
+  # ↓ *Optional* Enable or disable caching nil values.
+  ignore_empty_cache: true,
   # ↓ *Optional* modifier separator from Tailwind config
   separator: ":",
   # ↓ *Optional* prefix from Tailwind config

lib/tailwind_merge.rb

@@ -26,7 +26,7 @@ def initialize(config: {})
       end
 
       @class_utils = TailwindMerge::ClassUtils.new(@config)
-      @cache = LruRedux::Cache.new(@config[:cache_size])
+      @cache = LruRedux::Cache.new(@config[:cache_size], @config[:ignore_empty_cache])
     end
 
     def merge(classes)

lib/tailwind_merge/config.rb

@@ -84,6 +84,7 @@ module Config
 
     DEFAULTS = {
       cache_size: 500,
+      ignore_empty_cache: true,
       separator: ":",
       theme: {
         "colors" => [IS_ANY],

test/test_config.rb

@@ -7,6 +7,7 @@ def test_default_config_has_correct_types
     config = TailwindMerge::Config::DEFAULTS
 
     assert_equal(500, config[:cache_size])
+    assert(config[:ignore_empty_cache])
     refute(config[:nonexistent])
     assert_equal("block", config[:class_groups]["display"].first)
     assert_equal("auto", config[:class_groups]["overflow"].first["overflow"].first)