[ruby/irb] Fix column overflow on ls output

https://github.com/ruby/irb/commit/6115754623

lib/irb/cmd/ls.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "reline"
 require_relative "nop"
 require_relative "../color"
 
@@ -23,8 +24,11 @@ module IRB
       end
 
       class Output
+        MARGIN = "  "
+
         def initialize(grep: nil)
           @grep = grep
+          @line_width = screen_width
         end
 
         def dump(name, strs)
@@ -32,13 +36,44 @@ module IRB
           strs = strs.sort
           return if strs.empty?
 
+          # Attempt a single line
           print "#{Color.colorize(name, [:BOLD, :BLUE])}: "
-          if strs.size > 7
-            len = [strs.map(&:length).max, 16].min
-            puts; strs.each_slice(7) { |ss| puts "  #{ss.map { |s| "%-#{len}s" % s }.join("  ")}" }
-          else
-            puts strs.join("  ")
+          if fits_on_line?(strs, cols: strs.size, offset: "#{name}: ".length)
+            puts strs.join(MARGIN)
+            return
           end
+          puts
+
+          # Dump with the largest # of columns that fits on a line
+          cols = strs.size
+          until fits_on_line?(strs, cols: cols, offset: MARGIN.length) || cols == 1
+            cols -= 1
+          end
+          widths = col_widths(strs, cols: cols)
+          strs.each_slice(cols) do |ss|
+            puts ss.map.with_index { |s, i| "#{MARGIN}%-#{widths[i]}s" % s }.join
+          end
+        end
+
+        private
+
+        def fits_on_line?(strs, cols:, offset: 0)
+          width = col_widths(strs, cols: cols).sum + MARGIN.length * (cols - 1)
+          width <= @line_width - offset
+        end
+
+        def col_widths(strs, cols:)
+          cols.times.map do |col|
+            (col...strs.size).step(cols.size - 1).map do |i|
+              strs[i].length
+            end.max
+          end
+        end
+
+        def screen_width
+          Reline.get_screen_size.last
+        rescue Errno::EINVAL # in `winsize': Invalid argument - <STDIN>
+          79
         end
       end
       private_constant :Output