OK so we’re all completely clear on what this error means and what must be done to resolve it right? I mean with a meaningful error like that how can anyone be mistaken? Oh? What’s that? You still don’t know? Let’s be a bit more specific: System.IO.FileFormatException: Format error in package Better? Didn’t think so. It’s not an error message, that’s why. I’ll tell you what it is though, it’s stupid and even more stupid when you find out what causes it.

I came across this delightfully wishy-washy error when configuring an Umbraco 7 deployment pipeline in TeamCity and Octopus Deploy. The Umbraco .csproj MSBuild file referenced a bunch of files as you might expect but I also needed to add a .nuspec file which referenced a bunch of other files. Long-story-short, the error came about because the files specified by the .csproj overlapped with the files specified by the .nuspec file. There were about 1000-odd generated files that the NuGet packaging components in their infinite wisdom added to the .nupkg archive as many times as they were referenced. NuGet was able to do this silly thing without any complaints and inspecting the confused package in NuGet Package Explorer or 7Zip or Windows Zip gave no indication of any issues whatsoever. It was not until Octopus called on NuGet to unpack the archive for deployment that we got the above error.

Stupid, right? Stupid!

FYI: I was able to get to the bottom of this issue after 2 freaking days of pain when I eventually used JetBrains dotPeek to debug step-through the NuGet.Core and System.IO.Packaging components to see what on earth was going on. In the end it was this piece of code in System.IO.Packaging.Package that was causing the issue:

public PackagePartCollection GetParts()
{
...
	PackagePart[] partsCore = this.GetPartsCore();
	Dictionary dictionary = new Dictionary(partsCore.Length);
	for (int index = 0; index < partsCore.Length; ++index)
	{
	  PackUriHelper.ValidatedPartUri uri = (PackUriHelper.ValidatedPartUri) partsCore[index].Uri;
	  if (dictionary.ContainsKey(uri))
		throw new FileFormatException(MS.Internal.WindowsBase.SR.Get("BadPackageFormat"));
	  dictionary.Add(uri, partsCore[index]);
	  ...
	}
...
}

I mean, why would anyone consuming such a core piece of functionality as this API ever want to know anything about the conditions that led to the corruption of a 30MB package containing thousands of files? I mean it’s not like System.IO.Packaging was ever intended to be re-used all across the globe, right?

Anyways, here’s the error log for helping others with searching for this error and stuff.

[14:21:27]Step 1/1: Create Octopus Release
[14:21:27][Step 1/1] Step 1/1: Create Octopus release (OctopusDeploy: Create release)
[14:21:27][Step 1/1] Octopus Deploy
[14:21:27][Octopus Deploy] Running command:   octo.exe create-release --server https://octopus.url --apikey SECRET --project client-co-uk --enableservicemessages --channel Client Release --deployto Client CI --progress --packagesFolder=packagesFolder
[14:21:27][Octopus Deploy] Creating Octopus Deploy release
[14:21:27][Octopus Deploy] Octopus Deploy Command Line Tool, version 3.3.8+Branch.master.Sha.f8a34fc6097785d7d382ddfaa9a7f009f29bc5fb
[14:21:27][Octopus Deploy] 
[14:21:27][Octopus Deploy] Build environment is NoneOrUnknown
[14:21:27][Octopus Deploy] Using package versions from folder: packagesFolder
[14:21:27][Octopus Deploy] Package file: packagesFolder\Client.0.1.0-unstable0047.nupkg
[14:21:28][Octopus Deploy] System.IO.FileFormatException: Format error in package.
[14:21:28][Octopus Deploy]    at System.IO.Packaging.Package.GetParts()
[14:21:28][Octopus Deploy]    at System.IO.Packaging.Package.Open(Stream stream, FileMode packageMode, FileAccess packageAccess, Boolean streaming)
[14:21:28][Octopus Deploy]    at System.IO.Packaging.Package.Open(Stream stream)
[14:21:28][Octopus Deploy]    at NuGet.ZipPackage.GetManifestStreamFromPackage(Stream packageStream)
[14:21:28][Octopus Deploy]    at NuGet.ZipPackage.c__DisplayClassa.b__5()
[14:21:28][Octopus Deploy]    at NuGet.ZipPackage.EnsureManifest(Func`1 manifestStreamFactory)
[14:21:28][Octopus Deploy]    at NuGet.ZipPackage..ctor(String filePath, Boolean enableCaching)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.PackageVersionResolver.AddFolder(String folderPath)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.CreateReleaseCommand.c__DisplayClass1_0.b__5(String v)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.c__DisplayClass15_0.b__0(OptionValueCollection v)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.ActionOption.OnParseComplete(OptionContext c)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.Option.Invoke(OptionContext c)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.ParseValue(String option, OptionContext c)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.Parse(String argument, OptionContext c)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.c__DisplayClass26_0.b__0(String argument)
[14:21:28][Octopus Deploy]    at System.Linq.Enumerable.WhereArrayIterator`1.MoveNext()
[14:21:28][Octopus Deploy]    at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
[14:21:28][Octopus Deploy]    at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.OptionSet.Parse(IEnumerable`1 arguments)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.Options.Parse(IEnumerable`1 arguments)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Commands.ApiCommand.Execute(String[] commandLineArguments)
[14:21:28][Octopus Deploy]    at Octopus.Cli.Program.Main(String[] args)
[14:21:28][Octopus Deploy] Exit code: -3
[14:21:28][Octopus Deploy] Octo.exe exit code: -3
[14:21:28][Step 1/1] Unable to create or deploy release. Please check the build log for details on the error.
[14:21:28][Step 1/1] Step Create Octopus release (OctopusDeploy: Create release) failed

Update – 19th September 2018

I have just this morning helped a colleague through a permutation of this issue. We have recently upgraded TeamCity and it seems this has pushed the issue further down the pipeline. Where the above error would appear in TeamCity during packaging, it seems that the components have been updated to no longer throw the obscure error. My colleague found this issue now manifests when attempting to deploy through Octopus, throwing up the error: “Unable to download package: Item has already been added. Key in dictionary: …”

As before, here is a slightly redacted log to help with searching:

Acquiring packages
Making a list of packages to download
Downloading package CLIENT_NAME.Web version 6.0.0-beta0000 from feed: 'https://teamcity.CLIENT_NAME.com/httpAuth/app/nuget/v1/FeedService.svc/'
Unable to download package: 
Item has already been added. Key in dictionary: 'assets/fonts/fsmatthew-light-webfont.svg'  Key being added: 'assets/fonts/fsmatthew-light-webfont.svg'
System.ArgumentException: Item has already been added. Key in dictionary: 'assets/fonts/fsmatthew-light-webfont.svg'  Key being added: 'assets/fonts/fsmatthew-light-webfont.svg'