[ruby/irb] Print deprecation message for prompt_n methods

(https://github.com/ruby/irb/pull/691)

They were removed in #685, but we should still keep them to avoid breaking
changes to tools like Chef.

https://github.com/chef/chef/blob/533ff089479763f29045e4e6ddf388b73fc99338/lib/chef/shell.rb#L138

https://github.com/ruby/irb/commit/b585e0c835

1 files changed, 12 insertions, 0 deletions

diff --git a/test/irb/test_context.rb b/test/irb/test_context.rb
index 29c67392f3..dae0f8f6e4 100644
--- a/test/irb/test_context.rb
+++ b/test/irb/test_context.rb
@@ -90,6 +90,18 @@ module TestIRB
         ], out)
     end
 
+    def test_prompt_n_deprecation
+      irb = IRB::Irb.new(IRB::WorkSpace.new(Object.new))
+
+      out, err = capture_output do
+        irb.context.prompt_n = "foo"
+        irb.context.prompt_n
+      end
+
+      assert_include err, "IRB::Context#prompt_n is deprecated"
+      assert_include err, "IRB::Context#prompt_n= is deprecated"
+    end
+
     def test_output_to_pipe
       require 'stringio'
       input = TestInputMethod.new(["n=1"])