Bug 48734 - System.IO.Compression.ZipArchive.CreateEntry completely discards CompressionLevel argument
Summary: System.IO.Compression.ZipArchive.CreateEntry completely discards CompressionL...
Alias: None
Product: Class Libraries
Classification: Mono
Component: General ()
Version: 4.6.0 (C8)
Hardware: PC Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Marek Safar
Depends on:
Reported: 2016-12-02 17:19 UTC by Aaron Bockover [MSFT]
Modified: 2017-01-04 22:38 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Aaron Bockover [MSFT] 2016-12-02 17:19:19 UTC
Because System.IO.Compression.ZipArchive.CreateEntry completely discards the CompressionLevel argument, one cannot properly add zero-byte archive entries.

CompressionLevel.NoCompression should be translated to SharpZipLib's CompressionMethod.Stored to ensure the entry is stored but not compressed.

Without translating NoCompression to Stored, invalid archives are created:

$ unzip foo.zip
  inflating: subdir/untracked-single-byte-dependency
  inflating: subdir/untracked-zero-byte-dependency
  error:  invalid compressed data to inflate
  inflating: subdir/another/banana.jpg

The corefx System.IO.Compression (NuGet) correctly handles CompressionLevel.NoCompression:

$ unzip foo.zip
  inflating: subdir/untracked-single-byte-dependency
 extracting: subdir/untracked-zero-byte-dependency
  inflating: subdir/another/banana.jpg

It further does the right thing when the argument is omitted (defaulting to CompressionLevel.Optimal) by presumably setting the entry to stored instead of compressed if _no data was written to the archive stream_.

We will be using the NuGet from corefx from now on, since it also eliminates the SharpZipLib dependency, but I wanted to file this regardless.
Comment 1 Marek Safar 2017-01-04 22:38:56 UTC
mono master now uses CoreFX implementation which should resolved this issue as well.