Dynamic attribute optimizations (JsonApiClient#281)

* Add a unit test to benchmark dynamic attributes

This obviously is the wrong place for this, but it lets me run things
quickly. It'll come out before the end.

* Check has_attribute? before regexes for setters

Sample benchmark before:

    user     system      total        real
    read:   1.070000   0.000000   1.070000 (  1.077592)
    write:  1.130000   0.010000   1.140000 (  1.142294)

Sample benchmark after:

    user     system      total        real
    read:   0.580000   0.010000   0.590000 (  0.593090)
    write:  1.170000   0.000000   1.170000 (  1.180000)

* Use end_with? instead of regex engine

Not sure this matters yet.

* Use (& memoize) a DefaultKeyFormatter

This avoids repeatedly checking whether the class responds to
`#key_formatter`, calling `#key_formatter`, and checking whether its
result is nil.

Sample before benchmark:

       user     system      total        real
       read:   0.580000   0.000000   0.580000 (  0.576614)
       write:  1.130000   0.010000   1.140000 (  1.141003)

Sample after benchmark:

       user     system      total        real
       read:   0.570000   0.000000   0.570000 (  0.571892)
       write:  0.670000   0.010000   0.680000 (  0.672004)

* Auto-define basic attribute getters from method_missing

Sample before benchmark:

       user     system      total        real
       read:   0.570000   0.000000   0.570000 (  0.576622)
       write:  0.670000   0.000000   0.670000 (  0.672334)

Sample after benchmark:

       user     system      total        real
       read:   0.020000   0.000000   0.020000 (  0.013004)
       write:  0.640000   0.000000   0.640000 (  0.647726)

Because this defines a method for an attribute when the attribute is
accessed, I had to change the spec that checked for handling missing
methods for attributes, because it was accessing the attribute, and
therefore defining the method.

lib/json_api_client/helpers/dynamic_attributes.rb

@@ -24,7 +24,7 @@ def []=(key, value)
       end
 
       def respond_to_missing?(method, include_private = false)
-        if (method.to_s =~ /^(.*)=$/) || has_attribute?(method)
+        if has_attribute?(method) || method.to_s.end_with?('=')
           true
         else
           super
@@ -38,16 +38,19 @@ def has_attribute?(attr_name)
       protected
 
       def method_missing(method, *args, &block)
-        normalized_method = if key_formatter
-                              key_formatter.unformat(method.to_s)
-                            else
-                              method.to_s
-                            end
-
-        if normalized_method =~ /^(.*)=$/
-          set_attribute($1, args.first)
-        elsif has_attribute?(method)
-          attributes[method]
+        if has_attribute?(method)
+          self.class.class_eval do
+            define_method(method) do
+              attributes[method]
+            end
+          end
+          return send(method)
+        end
+
+        normalized_method = safe_key_formatter.unformat(method.to_s)
+
+        if normalized_method.end_with?('=')
+          set_attribute(normalized_method[0..-2], args.first)
         else
           super
         end
@@ -61,10 +64,20 @@ def set_attribute(name, value)
         attributes[name] = value
       end
 
+      def safe_key_formatter
+        @safe_key_formatter ||= (key_formatter || DefaultKeyFormatter.new)
+      end
+
       def key_formatter
         self.class.respond_to?(:key_formatter) && self.class.key_formatter
       end
 
+      class DefaultKeyFormatter
+        def unformat(method)
+          method.to_s
+        end
+      end
+
     end
   end
 end

test/unit/benchmark_dynamic_attributes_test.rb

@@ -0,0 +1,42 @@
+require 'test_helper'
+require 'benchmark'
+
+class BenchmarkDynamicAttributesTest < MiniTest::Test
+  def test_can_parse_global_meta_data
+    stub_request(:get, "http://example.com/articles/1")
+      .to_return(headers: {content_type: "application/vnd.api+json"}, body: {
+        data: {
+          type: "articles",
+          id: "1",
+          attributes: {
+            title: "Rails is Omakase"
+          }
+        },
+        meta: {
+          copyright: "Copyright 2015 Example Corp.",
+          authors: [
+            "Yehuda Katz",
+            "Steve Klabnik",
+            "Dan Gebhardt"
+          ]
+        },
+      }.to_json)
+
+    article = Article.find(1).first
+
+    assert_equal "Rails is Omakase", article.title
+    assert_equal "1", article.id
+
+    n = 10_000
+    puts
+    Benchmark.bm do |x|
+      x.report('read: ') { n.times { article.title; article.id } }
+      x.report('write:') do
+        n.times do
+          article.title = 'New title'
+          article.better_title = 'Better title'
+        end
+      end
+    end
+  end
+end

test/unit/resource_test.rb

@@ -73,13 +73,13 @@ def test_formatted_key_accessors
     end
 
     with_altered_config(Article, :json_key_format => :underscored_key) do
-      article = Article.new("foo-bar" => "baz")
+      article = Article.new("foo-bam" => "baz")
       # Does not recognize dasherized attributes, fall back to hash syntax
-      refute article.respond_to? :foo_bar
-      assert_equal("baz", article.send("foo-bar"))
-      assert_equal("baz", article.send(:"foo-bar"))
-      assert_equal("baz", article["foo-bar"])
-      assert_equal("baz", article[:"foo-bar"])
+      refute article.respond_to? :foo_bam
+      assert_equal("baz", article.send("foo-bam"))
+      assert_equal("baz", article.send(:"foo-bam"))
+      assert_equal("baz", article["foo-bam"])
+      assert_equal("baz", article[:"foo-bam"])
     end
   end