[ruby/tmpdir] Warn when environment variables skipped (fixes #2)

https://github.com/ruby/tmpdir/commit/af7b020a89

lib/tmpdir.rb

@@ -20,14 +20,21 @@ class Dir
 
   def self.tmpdir
     tmp = nil
-    [ENV['TMPDIR'], ENV['TMP'], ENV['TEMP'], @@systmpdir, '/tmp', '.'].each do |dir|
+    ['TMPDIR', 'TMP', 'TEMP', ['system temporary path', @@systmpdir], ['/tmp']*2, ['.']*2].each do |name, dir = ENV[name]|
       next if !dir
       dir = File.expand_path(dir)
-      if stat = File.stat(dir) and stat.directory? and stat.writable? and
-          (!stat.world_writable? or stat.sticky?)
+      stat = File.stat(dir) rescue next
+      case
+      when !stat.directory?
+        warn "#{name} is not a directory: #{dir}"
+      when !stat.writable?
+        warn "#{name} is not writable: #{dir}"
+      when stat.world_writable? && !stat.sticky?
+        warn "#{name} is world-writable: #{dir}"
+      else
         tmp = dir
         break
-      end rescue nil
+      end
     end
     raise ArgumentError, "could not find a temporary directory" unless tmp
     tmp

test/test_tmpdir.rb

@@ -21,16 +21,16 @@ class TestTmpdir < Test::Unit::TestCase
         envs.each do |e|
           tmpdirx = File.join(tmpdir, e)
           ENV[e] = tmpdirx
-          assert_not_equal(tmpdirx, Dir.tmpdir)
+          assert_not_equal(tmpdirx, assert_warn('') {Dir.tmpdir})
           File.write(tmpdirx, "")
-          assert_not_equal(tmpdirx, Dir.tmpdir)
+          assert_not_equal(tmpdirx, assert_warn(/not a directory/) {Dir.tmpdir})
           File.unlink(tmpdirx)
           ENV[e] = tmpdir
           assert_equal(tmpdir, Dir.tmpdir)
           File.chmod(0555, tmpdir)
-          assert_not_equal(tmpdir, Dir.tmpdir)
+          assert_not_equal(tmpdir, assert_warn(/not writable/) {Dir.tmpdir})
           File.chmod(0777, tmpdir)
-          assert_not_equal(tmpdir, Dir.tmpdir)
+          assert_not_equal(tmpdir, assert_warn(/world-writable/) {Dir.tmpdir})
           newdir = Dir.mktmpdir("d", tmpdir) do |dir|
             assert_file.directory? dir
             assert_equal(tmpdir, File.dirname(dir))