[API] Fixed the incorrect create method

Previously, the "Create" API has required the `:id` argument, although it is _not_ required
[https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html#_automatic_id_generation].

The REST API specs list it as required, though: <https://github.com/elastic/elasticsearch/blob/b47b399f000fce42eac0e00b9fdcf969122660ab/rest-api-spec/src/main/resources/rest-api-spec/api/create.json#L11>

This patch changes the logic of calling the `index` API method: when the `:id` is present,
it adds the `op_type` parameter, if it's missing, it simply calls the `index` method with parameters "as is".

Closes #491

(cherry picked from commit b1a8482)

elasticsearch-api/lib/elasticsearch/api/actions/create.rb

@@ -2,33 +2,40 @@ module Elasticsearch
   module API
     module Actions
 
-      # Create a document.
+      # Create a new document.
       #
-      # Enforce the _create_ operation when indexing a document --
-      # the operation will return an error when the document already exists.
+      # The API will create new document, if it doesn't exist yet -- in that case, it will return
+      # a `409` error (`version_conflict_engine_exception`).
       #
-      # @example Create a document
+      # You can leave out the `:id` parameter for the ID to be generated automatically
+      #
+      # @example Create a document with an ID
       #
       #     client.create index: 'myindex',
-      #                   type: 'mytype',
-      #                   id: '1',
-      #                   body: {
-      #                    title: 'Test 1',
-      #                    tags: ['y', 'z'],
-      #                    published: true,
-      #                    published_at: Time.now.utc.iso8601,
-      #                    counter: 1
-      #                   }
+      #                  type: 'doc',
+      #                  id: '1',
+      #                  body: {
+      #                   title: 'Test 1'
+      #                 }
       #
-      # @option (see Actions#index)
+      # @example Create a document with an auto-generated ID
       #
-      # (The `:op_type` argument is ignored.)
+      #     client.create index: 'myindex',
+      #                  type: 'doc',
+      #                  body: {
+      #                   title: 'Test 1'
+      #                 }
+      #
+      # @option (see Actions#index)
       #
-      # @see http://elasticsearch.org/guide/reference/api/index_/
+      # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html#_automatic_id_generation
       #
       def create(arguments={})
-        raise ArgumentError, "Required argument 'id' missing"  unless arguments[:id]
-        index arguments.update :op_type => 'create'
+        if arguments[:id]
+          index arguments.update :op_type => 'create'
+        else
+          index arguments
+        end
       end
     end
   end

elasticsearch-api/lib/elasticsearch/api/actions/index.rb

@@ -68,7 +68,7 @@ module Actions
       # @option arguments [Number] :version Explicit version number for concurrency control
       # @option arguments [String] :version_type Specific version type (options: internal, external, external_gte, force)
       #
-      # @see http://elasticsearch.org/guide/reference/api/index_/
+      # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html
       #
       def index(arguments={})
         raise ArgumentError, "Required argument 'index' missing" unless arguments[:index]

elasticsearch-api/test/unit/create_document_test.rb

@@ -7,12 +7,6 @@ class IndexDocumentTest < ::Test::Unit::TestCase
       context "Creating a document with the #create method" do
         subject { FakeClient.new }
 
-        should "require the ID" do
-          assert_raise ArgumentError do
-            subject.create :index => 'foo', :type => 'bar', :id => nil, :body => {:foo => 'bar'}
-          end
-        end
-
         should "perform the create request with a specific ID" do
           subject.expects(:perform_request).with do |method, url, params, body|
             assert_equal 'PUT', method
@@ -34,6 +28,27 @@ class IndexDocumentTest < ::Test::Unit::TestCase
 
           subject.create :index => 'foo', :type => 'bar/bam', :id => '123', :body => {}
         end
+
+        should "update the arguments with `op_type` when the `:id` argument is present" do
+          subject.expects(:perform_request).with do |method, url, params, body|
+            assert_equal 'foo/bar/1', url
+            assert_not_nil params[:op_type]
+            true
+          end.returns(FakeResponse.new)
+
+          subject.create :index => 'foo', :type => 'bar', :id => 1, :body => { :foo => 'bar' }
+        end
+
+        should "pass the arguments when the `:id` argument is missing" do
+          subject.expects(:perform_request).with do |method, url, params, body|
+            assert_equal 'foo/bar', url
+            assert_nil params[:op_type]
+            assert_nil params[:id]
+            true
+          end.returns(FakeResponse.new)
+
+          subject.create :index => 'foo', :type => 'bar', :body => { :foo => 'bar' }
+        end
       end
 
     end