Omit output if first line of multiline is too long

lib/irb.rb

@@ -750,10 +750,20 @@ def output_value(omit = false) # :nodoc:
       str = @context.inspect_last_value
       multiline_p = str.include?("\n")
       if omit
+        winwidth = @context.io.winsize.last
         if multiline_p
-          str.gsub!(/(\A.*?\n).*/m, "\\1...")
+          first_line = str.split("\n").first
+          result = @context.newline_before_multiline_output? ? (@context.return_format % first_line) : first_line
+          output_width = Reline::Unicode.calculate_width(result, true)
+          diff_size = output_width - Reline::Unicode.calculate_width(first_line, true)
+          if diff_size.positive? and output_width > winwidth
+            lines, _ = Reline::Unicode.split_by_width(first_line, winwidth - diff_size - 3)
+            str = "%s...\e[0m" % lines.first
+            multiline_p = false
+          else
+            str.gsub!(/(\A.*?\n).*/m, "\\1...")
+          end
         else
-          winwidth = @context.io.winsize.last
           output_width = Reline::Unicode.calculate_width(@context.return_format % str, true)
           diff_size = output_width - Reline::Unicode.calculate_width(str, true)
           if diff_size.positive? and output_width > winwidth

test/irb/test_context.rb

@@ -286,6 +286,82 @@ def test_omit_on_assignment
       assert_equal("", out)
     end
 
+    def test_omit_multiline_on_assignment
+      input = TestInputMethod.new([
+        "class A; def inspect; ([?* * 1000] * 3).join(%{\\n}); end; end; a = A.new\n",
+        "a\n"
+      ])
+      value = ([?* * 1000] * 3).join(%{\n})
+      value_first_line = (?* * 1000).to_s
+      irb = IRB::Irb.new(IRB::WorkSpace.new(Object.new), input)
+      irb.context.return_format = "=> %s\n"
+
+      irb.context.echo = true
+      irb.context.echo_on_assignment = false
+      irb.context.omit_on_assignment = true
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("=> \n#{value}\n", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+
+      input.reset
+      irb.context.echo = true
+      irb.context.echo_on_assignment = true
+      irb.context.omit_on_assignment = true
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("=> #{value_first_line[0..(input.winsize.last - 9)]}...\e[0m\n=> \n#{value}\n", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+
+      input.reset
+      irb.context.echo = true
+      irb.context.echo_on_assignment = true
+      irb.context.omit_on_assignment = false
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("=> \n#{value}\n=> \n#{value}\n", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+
+      input.reset
+      irb.context.echo = false
+      irb.context.echo_on_assignment = false
+      irb.context.omit_on_assignment = true
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+
+      input.reset
+      irb.context.echo = false
+      irb.context.echo_on_assignment = true
+      irb.context.omit_on_assignment = true
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+
+      input.reset
+      irb.context.echo = false
+      irb.context.echo_on_assignment = true
+      irb.context.omit_on_assignment = false
+      out, err = capture_io do
+        irb.eval_input
+      end
+      assert_empty err
+      assert_equal("", out)
+      irb.context.evaluate('A.remove_method(:inspect)', 0)
+    end
+
     def test_echo_on_assignment_conf
       # Default
       IRB.conf[:ECHO] = nil