The key must be a Symbol or an object that responds to #to_str

lib/fetch/form_data.rb

@@ -1,7 +1,11 @@
+require_relative 'symbol_to_str'
+
 module Fetch
   class FormData
     include Enumerable
 
+    using SymbolToStr
+
     def self.build(enumerable)
       data = FormData.new
 
@@ -19,23 +23,23 @@ def initialize
     attr_reader :entries
 
     def append(key, value)
-      @entries.push [key.to_s, value]
+      @entries.push [key.to_str, value]
     end
 
     def delete(key)
-      @entries.reject! {|k,| k == key.to_s }
+      @entries.reject! {|k,| k == key.to_str }
     end
 
     def get(key)
-      @entries.assoc(key.to_s)&.last
+      @entries.assoc(key.to_str)&.last
     end
 
     def get_all(key)
-      @entries.select {|k,| k == key.to_s }.map(&:last)
+      @entries.select {|k,| k == key.to_str }.map(&:last)
     end
 
     def has(key)
-      @entries.any? {|k,| k == key.to_s }
+      @entries.any? {|k,| k == key.to_str }
     end
 
     def keys

lib/fetch/headers.rb

@@ -1,7 +1,11 @@
+require_relative 'symbol_to_str'
+
 module Fetch
   class Headers
     include Enumerable
 
+    using SymbolToStr
+
     def initialize(init = [])
       @data = {}
 
@@ -11,31 +15,31 @@ def initialize(init = [])
     end
 
     def append(key, value)
-      (@data[key.to_s.downcase] ||= []) << value
+      (@data[key.to_str.downcase] ||= []) << value
     end
 
     def delete(key)
-      @data.delete key.to_s.downcase
+      @data.delete key.to_str.downcase
     end
 
     def entries
       @data.map {|k, vs| [k, vs.join(', ')] }
     end
 
     def get(key)
-      @data[key.to_s.downcase]&.join(', ')
+      @data[key.to_str.downcase]&.join(', ')
     end
 
     def has(key)
-      @data.key?(key.to_s.downcase)
+      @data.key?(key.to_str.downcase)
     end
 
     def keys
       @data.keys
     end
 
     def set(key, value)
-      @data[key.to_s.downcase] = [value]
+      @data[key.to_str.downcase] = [value]
     end
 
     def values

lib/fetch/symbol_to_str.rb

@@ -0,0 +1,9 @@
+module Fetch
+  module SymbolToStr
+    refine Symbol do
+      def to_str
+        to_s
+      end
+    end
+  end
+end

lib/fetch/url_search_params.rb

@@ -1,9 +1,13 @@
+require_relative 'symbol_to_str'
+
 require 'uri'
 
 module Fetch
   class URLSearchParams
     include Enumerable
 
+    using SymbolToStr
+
     def initialize(options = [])
       @entries = []
 
@@ -22,23 +26,23 @@ def initialize(options = [])
     attr_reader :entries
 
     def append(key, value)
-      @entries.push [key.to_s, value]
+      @entries.push [key.to_str, value]
     end
 
     def delete(key)
-      @entries.reject! {|k,| k == key.to_s }
+      @entries.reject! {|k,| k == key.to_str }
     end
 
     def get(key)
-      @entries.assoc(key.to_s)&.last
+      @entries.assoc(key.to_str)&.last
     end
 
     def get_all(key)
-      @entries.select {|k,| k == key.to_s }.map(&:last)
+      @entries.select {|k,| k == key.to_str }.map(&:last)
     end
 
     def has(key)
-      @entries.any? {|k,| k == key.to_s }
+      @entries.any? {|k,| k == key.to_str }
     end
 
     def keys

spec/fetch/form_data_spec.rb

@@ -20,7 +20,7 @@
       ['foo', 'bar']
     ])
 
-    data.append 'foo', 'baz'
+    data.append :foo, 'baz'
 
     expect(data.entries).to eq([
       ['foo', 'bar'],
@@ -68,7 +68,7 @@
     data.append 'foo', 'bar'
 
     expect(data.has('foo')).to be_truthy
-    expect(data.has('qux')).to be_falsey
+    expect(data.has('baz')).to be_falsey
   end
 
   example '#keys' do
@@ -85,12 +85,10 @@
     data = Fetch::FormData.new
 
     data.append 'foo', 'bar'
-    data.append 'foo', 'baz'
-
-    data.set 'foo', 'qux'
+    data.set    'foo', 'baz'
 
     expect(data.entries).to eq([
-      ['foo', 'qux']
+      ['foo', 'baz']
     ])
   end
 

spec/fetch/url_search_params_spec.rb

@@ -43,7 +43,7 @@
       ['foo', 'bar']
     ])
 
-    data.append 'foo', 'baz'
+    data.append :foo, 'baz'
 
     expect(data.entries).to eq([
       ['foo', 'bar'],