Docfx: Error extracting metadata for DLL files

[guardrex]

This error cropped up today for the first time.

Repo: https://github.com/aspnet/Blazor.Docs

Example: https://ci.appveyor.com/project/DanielRoth/blazor-docs/builds/21904702

DocFX Version Used: 2.40.8

Build failed.
[19-01-26 06:52:09.802]Error:Error extracting metadata for C:/projects/blazor-docs/src/Microsoft.AspNetCore.Blazor.Browser.dll,C:/projects/blazor-docs/src/Microsoft.AspNetCore.Blazor.dll,C:/projects/blazor-docs/src/Microsoft.AspNetCore.Blazor.Server.dll,C:/projects/blazor-docs/src/Microsoft.JSInterop.dll,C:/projects/blazor-docs/src/Mono.WebAssembly.Interop.dll: System.ArgumentNullException: Value cannot be null.
Parameter name: key
   at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at Microsoft.DocAsCode.Metadata.ManagedReference.MergeCommentsHelper.GetAllItemByCommentId(Dictionary`2 items, MetadataItem item)
   at Microsoft.DocAsCode.Metadata.ManagedReference.MergeCommentsHelper.PatchMetadataItem(MetadataItem assembly, IEnumerable`1 list)
   at Microsoft.DocAsCode.Metadata.ManagedReference.MergeCommentsHelper.MergeComments(MetadataItem item, IEnumerable`1 commentFiles)
   at Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.<SaveAllMembersFromCacheAsync>d__13.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.<ExtractMetadataAsync>d__11.MoveNext()
    0 Warning(s)
    1 Error(s)
Command exited with code 1

[UPDATE] If I drop to the last patch release ...

- cinst docfx --version 2.40.7

... it builds. https://github.com/aspnet/Blazor.Docs/pull/387

[scottcurrie]

Just wanted to note that we are seeing this same regression between 2.40.7 and 2.40.8. If you need any additional information, I am happy to provide it.

[superyyrrzz]

This must be related to #3936 . We will fix it ASAP.

[mezzo9]

Is there a way to get the source for a previous working version that does not have this error?
My assumption was that the 'stable' branch is the answer, but still, the same error happens on that.
Thanks,

[guardrex]

@mezzo9 ... Yes, just grab a prior release to 2.40.8 from https://github.com/dotnet/docfx/releases ... 2.40.7 seems ok. I have our AppVeyor using 2.40.7 ... no :boom: at the moment.

[mezzo9]

Thank you very much @guardrex.
I also got the latest from dev, and the fix @superyyrrzz provided worked.
everything is back to normal now.
Thanks all for your help.

[superyyrrzz]

2.40.9 fixed this issue. It is available on Nuget, and will soon available on Chocolatey once approved.

Thank you for reporting the issue!

[Garonenur]

Is this a new issue then? seen today with nuget docfx.console v2.49.0.

Build failed.
1>  [20-02-26 03:59:37.576]Error:Error extracting metadata for [name].csproj: System.ArgumentNullException: Der Wert darf nicht NULL sein.
1>  Parametername: key
1>     bei System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
1>     bei System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
1>     bei System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.CopyInherited.Copy(MetadataItem dest, String srcName, ResolverContext context)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.CopyInherited.InheritDoc(MetadataItem dest, ResolverContext context)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.CopyInherited.<>c__DisplayClass0_0.<Run>b__1(MetadataItem current, MetadataItem parent)
1>     bei Microsoft.DocAsCode.Common.TreeIterator.Preorder[T](T current, T parent, Func`2 childrenGetter, Func`3 action)
1>     bei Microsoft.DocAsCode.Common.TreeIterator.Preorder[T](T current, T parent, Func`2 childrenGetter, Func`3 action)
1>     bei Microsoft.DocAsCode.Common.TreeIterator.Preorder[T](T current, T parent, Func`2 childrenGetter, Func`3 action)
1>     bei Microsoft.DocAsCode.Common.TreeIterator.Preorder[T](T current, T parent, Func`2 childrenGetter, Func`3 action)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.CopyInherited.Run(MetadataModel yaml, ResolverContext context)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.YamlMetadataResolver.ExecutePipeline(MetadataModel yaml, ResolverContext context)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.YamlMetadataResolver.ResolveMetadata(Dictionary`2 allMembers, Dictionary`2 allReferences, Boolean preserveRawInlineComments)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.<ResolveAndExportYamlMetadata>d__19.MoveNext()
1>     bei System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
1>     bei System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.<SaveAllMembersFromCacheAsync>d__13.MoveNext()
1>  --- Ende der Stapelüberwachung vom vorhergehenden Ort, an dem die Ausnahme ausgelöst wurde ---
1>     bei System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
1>     bei System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
1>     bei Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.<ExtractMetadataAsync>d__11.MoveNext()
1>      0 Warning(s)
1>      1 Error(s)

[otto-gebb]

A workaround that fixed the error for me:

• In docfx.json specify a glob pattern for .cs files instead of the .csproj file.
• Set the MSBUILD_EXE_PATH environment variable.
  $env:MSBUILD_EXE_PATH="c:\Program Files\dotnet\sdk\3.1.101\MSBuild.dll"

UPD: After updating to 2.49 things got better: building of docs succeeds, but only if I clean up after building the dll via dotnet build, i.e. remove all the bin and obj folders.