From: Brian Candler <b.candler@...>
Date: 2010-08-27T17:44:00+09:00
Subject: Re: Rubyzip - `dup': can't dup NilClass (TypeError)

Scott Bronson wrote:
> require 'open-uri'
> require 'zip/zipfilesystem'
> open('http://www.vim.org/scripts/download_script.php?src_id=11978', 
> 'rb') { |f| Zip::ZipFile.open(f) }

For me (with ruby 1.8.7 and rubyzip-0.9.4) that dies with "cannot 
convert Tempfile to String", but if I download the zip locally and then 
do Zip::ZipFile.open("ert.zip") then I get the same error as you.

> For some reason, read_c_dir_entry is returning nil.  I haven't tried to 
> figure out why since I'm not familiar with the internals of a zipfile.

I suggest you apply the following patch:

--- rubyzip-0.9.4/lib/zip/zip.rb.orig  2010-06-16 21:38:16.755077969 
+0100
+++ rubyzip-0.9.4/lib/zip/zip.rb  2010-08-27 09:34:19.673351372 +0100
@@ -658,8 +658,8 @@
       entry = new(io.path)
       entry.read_c_dir_entry(io)
       return entry
-    rescue ZipError
-      return nil
+    #rescue ZipError
+    #  return nil
     end

     def file_stat(path)  # :nodoc:

Then you get a more helpful error:

/var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:645:in 
`read_c_dir_entry': unknown file type 00 (Zip::ZipInternalError)
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:659:in 
`read_c_dir_entry'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1255:in 
`read_central_directory_entries'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1254:in 
`times'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1254:in 
`read_central_directory_entries'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1261:in 
`read_from_stream'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1392:in 
`initialize'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1392:in 
`open'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1392:in 
`initialize'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1410:in `new'
  from /var/lib/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1410:in 
`open'

To be honest, I have no idea why rubyzip is catching these errors and 
returning nil, instead of letting them propagate upwards. All it does is 
make a more obscure error later on ("cannot dup nil")

With another patch:

--- rubyzip-0.9.4/lib/zip/zip.rb.orig  2010-06-16 21:38:16.755077969 
+0100
+++ rubyzip-0.9.4/lib/zip/zip.rb  2010-08-27 09:38:07.475854345 +0100
@@ -642,7 +642,7 @@
         when 012
           @ftype = :symlink
         else
-          raise ZipInternalError, "unknown file type #{'0%o' % 
(@externalFileAttributes >> 28)}"
+          raise ZipInternalError, "unknown file type #{'0%o' % 
(@externalFileAttributes >> 28)} for entry #{@name.inspect}"
         end
       else
         if name_is_directory?

you can see that the affected entry is .DS_Store. That unpacks as a 
regular file from unix unzip.

I don't know why this entry happens to have a type of 0, but you can 
allow it like this:

--- rubyzip-0.9.4/lib/zip/zip.rb.orig  2010-06-16 21:38:16.755077969 
+0100
+++ rubyzip-0.9.4/lib/zip/zip.rb  2010-08-27 09:41:14.853352187 +0100
@@ -637,12 +637,12 @@
         case (@externalFileAttributes >> 28)
         when 04
           @ftype = :directory
-        when 010
+        when 010, 00
           @ftype = :file
         when 012
           @ftype = :symlink

Anyway, since you have a good test case for this, I suggest you post it 
to the rubyzip mailing list or tracker, if there is one.

Regards,

Brian.
-- 
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