JRuby

Faulty interaction between Dir.chdir, File.chmod and Test::Unit

Details

  • Type: Bug Bug
  • Status: Resolved Resolved
  • Priority: Major Major
  • Resolution: Fixed
  • Affects Version/s: JRuby 1.1.6
  • Fix Version/s: None
  • Component/s: Core Classes/Modules
  • Labels:
    None
  • Environment:
    JRuby 1.1.6, OS X, Java 1.5
  • Testcase included:
    yes
  • Number of attachments :
    0

Description

Somehow, someway, the File.chmod method is failing when interacting with Dir.chdir and Test::Unit This sample program demonstrates the problem:

# test.rb
#
# Create this file as 'test/test.rb'
# Run from the parent directory, e.g. jruby test/test.rb
#
require 'test/unit'

class TC_Writable < Test::Unit::TestCase
   def setup
      Dir.chdir('test') # Comment this out and it works
      @file = 'foo.doc'
      File.open(@file, 'w'){}
   end

   def test_filetest
      File.chmod(0644, @file)
      assert_equal(true, File.writable?(@file))

      File.chmod(0444, @file)
      assert_equal(false, File.writable?(@file))
   end

   def teardown
      File.delete(@file) if File.exists?(@file)
      @file = nil
   end
end

When I run standalone programs, however, it works fine. This leads me to believe there's some sort of interaction going on with Test::Unit, but I couldn' tell you what.

Regards,

Dan

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Daniel Berger added a comment -

BTW, here's my output:

$ jruby test/test.rb 
Loaded suite test/test
Started
F
Finished in 0.113602 seconds.

  1) Failure:
test_filetest(TC_Writable) [test/test.rb:21]:
<false> expected but was
<true>.

1 tests, 2 assertions, 1 failures, 0 errors
Show
Daniel Berger added a comment - BTW, here's my output: $ jruby test/test.rb Loaded suite test/test Started F Finished in 0.113602 seconds. 1) Failure: test_filetest(TC_Writable) [test/test.rb:21]: <false> expected but was <true>. 1 tests, 2 assertions, 1 failures, 0 errors
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Charles Oliver Nutter added a comment -

I think this is related to a known issue with chdir: we can't do it safely, so we fake it. For chdir, POSIX allows only a per-process cwd. So whenever you change it, all threads in a given process see that change. If other threads depend on cwd not changing, they break in nasty ways. In JRuby's case, we can't actually call the POSIX chdir because it would change it for the entire JVM. That would at least not be polite and at most crash other applications running in the same JVM. So we fake it, and try to juggle paths whenever we make calls that are based on cwd. In this case, we're probably not juggling the path enough so that a native chmod call can succeed.

The best workaround is not to use chdir at all. Slightly less great would be to ensure you're using full paths, which we may chdir correctly. I agree that it's a rather cumbersome state of affairs, but without chdir being per-thread at the POSIX level no implementation can support it completely and reliably. Don't use it.

Show
Charles Oliver Nutter added a comment - I think this is related to a known issue with chdir: we can't do it safely, so we fake it. For chdir, POSIX allows only a per-process cwd. So whenever you change it, all threads in a given process see that change. If other threads depend on cwd not changing, they break in nasty ways. In JRuby's case, we can't actually call the POSIX chdir because it would change it for the entire JVM. That would at least not be polite and at most crash other applications running in the same JVM. So we fake it, and try to juggle paths whenever we make calls that are based on cwd. In this case, we're probably not juggling the path enough so that a native chmod call can succeed. The best workaround is not to use chdir at all. Slightly less great would be to ensure you're using full paths, which we may chdir correctly. I agree that it's a rather cumbersome state of affairs, but without chdir being per-thread at the POSIX level no implementation can support it completely and reliably. Don't use it.
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Thomas E Enebo added a comment -

In this case couldn't we check to see what the faked out chdir is and use that for our FileTest methods? It is true we cannot fake chdir all the time, but these should be ok to do. Actually all File/Dir-based methods should be doing this? We probably need to do same resolution as JRubyFile (or perhaps even just use it before calling posix function).

Show
Thomas E Enebo added a comment - In this case couldn't we check to see what the faked out chdir is and use that for our FileTest methods? It is true we cannot fake chdir all the time, but these should be ok to do. Actually all File/Dir-based methods should be doing this? We probably need to do same resolution as JRubyFile (or perhaps even just use it before calling posix function).
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Charles Oliver Nutter added a comment -

We probably could, but I think we're fighting a losing battle trying to propagate chdir across all calls. No reason not to fix obvious places, of course.

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Charles Oliver Nutter added a comment - We probably could, but I think we're fighting a losing battle trying to propagate chdir across all calls. No reason not to fix obvious places, of course.
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Logan Barnett added a comment -

I was able to workaround this issue myself by calling File.expand_path on the path I was passing into chmod (I think Charlie said this same/similar thing to some effect).

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Logan Barnett added a comment - I was able to workaround this issue myself by calling File.expand_path on the path I was passing into chmod (I think Charlie said this same/similar thing to some effect).
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Charles Oliver Nutter added a comment -

Working on master as of now. Not sure when it was fixed, but it's fixed.

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Charles Oliver Nutter added a comment - Working on master as of now. Not sure when it was fixed, but it's fixed.

People

  • Assignee:
    Charles Oliver Nutter
    Reporter:
    Daniel Berger
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    Updated:
    Resolved: