Fix double return tag.

lib/yard/autoload.rb

@@ -64,6 +64,11 @@ module CodeObjects
   # parsing phase. This allows YARD as well as any custom extension to
   # analyze source and generate {CodeObjects} to be stored for later use.
   module Handlers
+    # Shared logic between C and Ruby handlers.
+    module Common
+      autoload :MethodHandler,            __p('handlers/common/method_handler')
+    end
+
     # CRuby Handlers
     # @since 0.8.0
     module C

lib/yard/handlers/c/handler_methods.rb

@@ -5,6 +5,7 @@ module C
       module HandlerMethods
         include Parser::C
         include CodeObjects
+        include Common::MethodHandler
 
         def handle_class(var_name, class_name, parent, in_module = nil)
           parent = nil if parent == "0"
@@ -67,7 +68,7 @@ def handle_method(scope, var_name, name, func_name, _source_file = nil)
             register_visibility(obj, visibility)
             find_method_body(obj, func_name)
             obj.explicit = true
-            obj.add_tag(Tags::Tag.new(:return, '', 'Boolean')) if name =~ /\?$/
+            add_predicate_return_tag(obj) if name =~ /\?$/
           end
         end
 

lib/yard/handlers/common/method_handler.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module YARD::Handlers
+  module Common
+    # Shared functionality between Ruby and C method handlers.
+    module MethodHandler
+      # @param [MethodObject] obj
+      def add_predicate_return_tag(obj)
+        if obj.tag(:return) && (obj.tag(:return).types || []).empty?
+          obj.tag(:return).types = ['Boolean']
+        elsif obj.tag(:return).nil?
+          unless obj.tags(:overload).any? {|overload| overload.tag(:return) }
+            obj.add_tag(YARD::Tags::Tag.new(:return, "", "Boolean"))
+          end
+        end
+      end
+    end
+  end
+end

lib/yard/handlers/ruby/method_handler.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 # Handles a method definition
 class YARD::Handlers::Ruby::MethodHandler < YARD::Handlers::Ruby::Base
+  include YARD::Handlers::Common::MethodHandler
+
   handles :def, :defs
 
   process do
@@ -39,13 +41,7 @@ class YARD::Handlers::Ruby::MethodHandler < YARD::Handlers::Ruby::Base
         extended method_added method_removed method_undefined).include?(meth)
       obj.add_tag(YARD::Tags::Tag.new(:private, nil))
     elsif meth.to_s =~ /\?$/
-      if obj.tag(:return) && (obj.tag(:return).types || []).empty?
-        obj.tag(:return).types = ['Boolean']
-      elsif obj.tag(:return).nil?
-        unless obj.tags(:overload).any? {|overload| overload.tag(:return) }
-          obj.add_tag(YARD::Tags::Tag.new(:return, "", "Boolean"))
-        end
-      end
+      add_predicate_return_tag(obj)
     end
 
     if obj.has_tag?(:option)

spec/handlers/c/method_handler_spec.rb

@@ -213,6 +213,7 @@
     foo = Registry.at('Foo#foo?')
     expect(foo.docstring).to eq 'DOCSTRING'
     expect(foo.tag(:return).types).to eq ['Boolean']
+    expect(foo.tags(:return).size).to eq 1
   end
 
   it "does not add return tag if return tags exist" do
@@ -226,6 +227,7 @@
     eof
     foo = Registry.at('Foo#foo?')
     expect(foo.tag(:return).types).to eq ['String']
+    expect(foo.tags(:return).size).to eq 1
   end
 
   it "handles casted method names" do