Avoid deprecated multi_json APIs while retaining legacy compatibility

jsonpath.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |s|
   s.licenses    = ['MIT']
 
   # dependencies
-  s.add_runtime_dependency 'multi_json'
+  s.add_runtime_dependency 'multi_json', '>= 1.3'
   s.add_development_dependency 'bundler'
   s.add_development_dependency 'code_stats'
   s.add_development_dependency 'minitest', '~> 2.2.0'

lib/jsonpath.rb

@@ -142,7 +142,13 @@ def self.for(obj_or_str)
   private
 
   def self.process_object(obj_or_str, opts = {})
-    obj_or_str.is_a?(String) ? MultiJson.decode(obj_or_str, max_nesting: opts[:max_nesting]) : obj_or_str
+    return obj_or_str unless obj_or_str.is_a?(String)
+
+    if defined?(MultiJSON)
+      MultiJSON.parse(obj_or_str, max_nesting: opts[:max_nesting])
+    else
+      MultiJson.load(obj_or_str, max_nesting: opts[:max_nesting])
+    end
   end
 
   def deep_clone

test/test_jsonpath.rb

@@ -4,6 +4,8 @@
 require 'phocus'
 require 'jsonpath'
 require 'json'
+require 'open3'
+require 'rbconfig'
 
 class TestJsonpath < MiniTest::Unit::TestCase
   def setup
@@ -17,6 +19,23 @@ def test_bracket_matching
     assert_equal [9], JsonPath.new('$.store.book[0].price').on(@object)
   end
 
+  def test_parse_string_without_deprecation_warnings
+    # Use a fresh process because newer multi_json releases warn only once per API.
+    code = <<~RUBY
+      gem 'multi_json', '#{Gem.loaded_specs['multi_json'].version}'
+      require 'jsonpath'
+      puts JsonPath.new('$.credential.access_token').first(
+        '{"credential":{"access_token":"example-token"}}'
+      )
+    RUBY
+    stdout, stderr, status = Open3.capture3(
+      RbConfig.ruby, '-W2', '-I', File.expand_path('../lib', __dir__), '-e', code
+    )
+    assert status.success?, stderr
+    assert_equal "example-token\n", stdout
+    assert_equal '', stderr
+  end
+
   def test_lookup_direct_path
     assert_equal 7, JsonPath.new('$.store.*').on(@object).first['book'].size
   end
@@ -1189,7 +1208,8 @@ def test_raise_max_nesting_error
       }
     }.to_json
 
-    assert_raises(MultiJson::ParseError) { JsonPath.new('$.a', max_nesting: 1).on(json) }
+    json_parser = defined?(MultiJSON) ? MultiJSON : MultiJson
+    assert_raises(json_parser::ParseError) { JsonPath.new('$.a', max_nesting: 1).on(json) }
   end
 
   def test_linefeed_in_path_error