Create Fields using unsorted positional types

This change allows for positional types, types with an accompanying position value,
such as those defined by a Hash without names, to be unsorted.
The initializer now sorts those positional types.

google-cloud-spanner/lib/google/cloud/spanner/fields.rb

@@ -107,14 +107,22 @@ def initialize types
             raise ArgumentError, "can only accept Array or Hash"
           end
 
-          # Verify positional arguments are in order
-          types.each_with_index do |type, index|
-            if type.is_a?(Array) && type.first.is_a?(Integer)
-              raise "types must be in order" if type.first != index
-            end
+          sorted_types, unsorted_types = types.partition do |type|
+            type.is_a?(Array) && type.count == 2 && type.first.is_a?(Integer)
+          end
+
+          if sorted_types.count != sorted_types.map(&:first).uniq.count
+            raise ArgumentError, "cannot specify position more than once"
           end
 
-          @grpc_fields = types.map { |type| to_grpc_field type }
+          @grpc_fields = Array.new(types.count) do |index|
+            sorted_type = sorted_types.assoc index
+            if sorted_type
+              to_grpc_field sorted_type.last
+            else
+              to_grpc_field unsorted_types.shift
+            end
+          end
         end
 
         ##

google-cloud-spanner/test/google/cloud/spanner/fields/initializer_test.rb

@@ -46,13 +46,12 @@
   end
 
   it "creates with an unsorted mixed array of fields" do
-    skip "Not yet implemented"
     fields = Google::Cloud::Spanner::Fields.new [[:name, :STRING], :BOOL, [0, :INT64]]
 
     fields.types.must_equal [:INT64, :STRING, :BOOL]
     fields.keys.must_equal [0, :name, 2]
     fields.pairs.must_equal [[0, :INT64], [:name, :STRING], [2, :BOOL]]
-    fields.to_a.must_equal [:INT64, [:name, :STRING], :BOOL]
+    fields.to_a.must_equal [:INT64, :STRING, :BOOL]
     fields.to_h.must_equal({ 0=>:INT64, name: :STRING, 2=>:BOOL })
   end
 
@@ -87,13 +86,12 @@
   end
 
   it "creates with an unsorted mixed hash of fields" do
-    skip "Not yet implemented"
     fields = Google::Cloud::Spanner::Fields.new name: :STRING, 2=>:BOOL, 0=>:INT64
 
     fields.types.must_equal [:INT64, :STRING, :BOOL]
     fields.keys.must_equal [0, :name, 2]
     fields.pairs.must_equal [[0, :INT64], [:name, :STRING], [2, :BOOL]]
-    fields.to_a.must_equal [:INT64, [:name, :STRING], :BOOL]
+    fields.to_a.must_equal [:INT64, :STRING, :BOOL]
     fields.to_h.must_equal({ 0=>:INT64, name: :STRING, 2=>:BOOL })
   end
 end