Remove MultiJson from the list of dependencies

Fixes #1. For context, see #1 and
intridea/multi_json#113 (comment).

README.md

@@ -30,16 +30,13 @@ PersonSerializer.new(person).to_json #=> '{"name":"John Doe",...}'
 ## JSON serialization
 
 Granola doesn't make assumptions about your code, so it shouldn't depend on a
-specific JSON backend. It uses [MultiJson][] to serialize your objects with your
-favorite backend.
+specific JSON backend. It defaults to the native JSON backend, but you're free
+to change it. For example, if you were using [Yajl][]:
 
-Try to avoid using the default, which is the `stdlib`'s pure-ruby JSON library,
-since it's slow. If in doubt, I like [Yajl][].
-
-If you want to pass options to `MultiJson` (like `pretty: true`), any keywords
-passed to `#to_json` will be forwarded to `MultiJson.dump`.
+``` ruby
+Granola.json = ->(obj, **opts) { Yajl::Encoder.encode(obj, opts) }
+```
 
-[MultiJson]: https://github.com/intridea/multi_json
 [Yajl]: https://github.com/brianmario/yajl-ruby
 
 ## Handling lists of models

granola.gemspec

@@ -20,9 +20,7 @@ Gem::Specification.new do |s|
     "lib/granola/caching.rb",
   ]
 
-  s.add_dependency "multi_json", "~> 1.10"
-
   s.add_development_dependency "cutest", "~> 1.2"
-  s.add_development_dependency "rack", "~> 1.5"
+  s.add_development_dependency "rack", "~> 2.5"
 end
 

lib/granola.rb

@@ -1,7 +1,23 @@
-require "multi_json"
 require "granola/version"
+require "json"
 
 module Granola
+  class << self
+    # Public: Get/Set a Proc that takes an Object and a Hash of options and
+    # returns a JSON String.
+    #
+    # The default implementation uses the standard library's JSON module, but
+    # you're welcome to swap it out.
+    #
+    # Example:
+    #
+    #   require "yajl"
+    #   Granola.json = ->(obj, **opts) { Yajl::Encoder.encode(obj, opts) }
+    attr_accessor :json
+  end
+
+  self.json = ->(obj, **opts) { JSON.dump(obj) }
+
   # A Serializer describes how to serialize a certain type of object, by
   # declaring the structure of JSON objects.
   class Serializer
@@ -35,13 +51,13 @@ def attributes
       fail NotImplementedError
     end
 
-    # Public: Generate the JSON string using the current MultiJson adapter.
+    # Public: Generate the JSON String.
     #
-    # **options - Any options valid for `MultiJson.dump`.
+    # **options - Any options to be passed to the `Granola.json` Proc.
     #
     # Returns a String.
     def to_json(**options)
-      MultiJson.dump(attributes, options)
+      Granola.json.(attributes, options)
     end
 
     # Public: Returns the MIME type generated by this serializer. By default

test/serialize_test.rb

@@ -50,3 +50,14 @@ def mime_type
     assert_equal %q|[{"a":1,"b":2},{"a":3,"b":4}]|, serializer.to_json
   end
 end
+
+scope do
+  prepare do
+    Granola.json = ->(obj, **opts) { "success!" }
+  end
+
+  test "serializes with a custom json backend" do
+    serializer = OpenStructSerializer.new(OpenStruct.new)
+    assert_equal "success!", serializer.to_json
+  end
+end