Merge pull request #690 from deivid-rodriguez/rb_readline_does_not_re…

…spond_to_call

Restore old check on `completion_proc=`

lib/thor/line_editor/readline.rb

@@ -13,7 +13,10 @@ def self.available?
       def readline
         if echo?
           ::Readline.completion_append_character = nil
-          ::Readline.completion_proc = completion_proc
+          # rb-readline does not allow Readline.completion_proc= to receive nil.
+          if complete = completion_proc
+            ::Readline.completion_proc = complete
+          end
           ::Readline.readline(prompt, add_to_history?)
         else
           super

spec/line_editor/readline_spec.rb

@@ -23,14 +23,14 @@
   describe "#readline" do
     it "invokes the readline library" do
       expect(::Readline).to receive(:readline).with("> ", true).and_return("foo")
-      expect(::Readline).to receive(:completion_proc=)
+      expect(::Readline).to_not receive(:completion_proc=)
       editor = Thor::LineEditor::Readline.new("> ", {})
       expect(editor.readline).to eq("foo")
     end
 
     it "supports the add_to_history option" do
       expect(::Readline).to receive(:readline).with("> ", false).and_return("foo")
-      expect(::Readline).to receive(:completion_proc=)
+      expect(::Readline).to_not receive(:completion_proc=)
       editor = Thor::LineEditor::Readline.new("> ", :add_to_history => false)
       expect(editor.readline).to eq("foo")
     end