Ignore nonpositive console size overrides

Rakefile

@@ -35,6 +35,7 @@ Rake::TestTask.new(:test) do |t|
   elsif RUBY_ENGINE == "jruby"
     t.libs.unshift "jruby/lib"
   end
+  t.libs << "lib"
   t.libs << "test/lib"
   t.ruby_opts << "-rhelper"
   t.test_files = FileList["test/**/test_*.rb"]

lib/io/console/size.rb

@@ -1,9 +1,11 @@
 # frozen_string_literal: false
 # fallback to console window size
 def IO.default_console_size
+  lines = ENV["LINES"].to_i
+  columns = ENV["COLUMNS"].to_i
   [
-    ENV["LINES"].to_i.nonzero? || 25,
-    ENV["COLUMNS"].to_i.nonzero? || 80,
+    lines.positive? ? lines : 25,
+    columns.positive? ? columns : 80,
   ]
 end
 

test/io/console/test_io_console.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: false
 begin
   require 'io/console'
+  require 'io/console/size'
   require 'test/unit'
   require 'pty'
 rescue LoadError
@@ -691,7 +692,7 @@ def test_ttyname
   if noctty
     require 'tempfile'
     NOCTTY = noctty
-    def run_noctty(src)
+    def run_noctty(src, require: "io/console", env: nil)
       t = Tempfile.new("noctty_out")
       t.close
       t2 = Tempfile.new("noctty_run")
@@ -701,12 +702,13 @@ def run_noctty(src)
         '-e', 'open(ARGV[0], "w") {|f|',
         '-e',   'STDOUT.reopen(f)',
         '-e',   'STDERR.reopen(f)',
-        '-e',   'require "io/console"',
+        '-e',   "require #{require.dump}",
         '-e',   "f.puts (#{src}).inspect",
         '-e',   'f.flush',
         '-e',   'File.unlink(ARGV[1])',
         '-e', '}',
         '--', t.path, t2.path]
+      cmd.unshift(env) if env
       assert_ruby_status(cmd, rubybin: NOCTTY[0])
       30.times do
         break unless File.exist?(t2.path)
@@ -725,6 +727,25 @@ def test_noctty
         assert_equal(["nil"], run_noctty("STDIN.ttyname rescue $!"))
       end
     end
+
+    def test_default_console_size
+      [
+        [40, 100],
+        [nil, 50],
+        [30, nil],
+        [0, 50],
+        [30, 0],
+        [-1, 50],
+        [30, -1],
+      ].each do |lines, columns|
+        result = run_noctty("IO.console_size",
+                            require: "io/console/size",
+                            env: {"LINES"=>lines&.to_s, "COLUMNS"=>columns&.to_s})
+        lines = 25 unless lines&.positive?
+        columns = 80 unless columns&.positive?
+        assert_equal([[lines, columns].inspect], result)
+      end
+    end
   end
 end