Error extracting metadata for project. An item with the same key has already been added.

[ghost]

DocFX Version Used:

2.40.4.0

Template used: (default or statictoc or contain custom template)

default

Steps to Reproduce:

1. Ran the following docfx.json on an internal project (cannot supply)

{
  "metadata": [
    {
      "dest": "api",
      "disableDefaultFilter": false,
      "disableGitFeatures": false,
      "src": [
        {
          "exclude": ["**/bin/**", "**/obj/**"],
          "files": [
            "myproject.csproj"
          ],
          "src": ".."
        }
      ]
    }
  ],
  "build": {
    "cleanupCacheHistory": false,
    "content": [
      {
        "files": [
          "api/**.yml",
          "api/index.md"
        ]
      },
      {
        "files": [
          "articles/**.md",
          "articles/**/toc.yml",
          "toc.yml",
          "*.md"
        ]
      }
    ],
    "dest": "_site",
    "disableGitFeatures": false,
    "fileMetadataFiles": [],
    "globalMetadataFiles": [],
    "keepFileLink": false,
    "markdownEngineName": "markdig",
    "noLangKeyword": false,
    "overwrite": [
      {
        "exclude": [
          "bin/**",
          "obj/**",
          "_site/**"
        ],
        "files": [
          "apidoc/**.md"
        ]

      }
    ],
    "postProcessors": [],
    "resource": [
      {
        "files": [
          "images/**"
        ]
      }
    ],
    "template": [
      "default"
    ]
  }
}

Expected Behavior:

Documentation is generated

Actual Behavior:

[18-12-18 01:06:14.294]Info:Config file docfx.json found, start generating metadata...
[18-12-18 01:06:14.506]Info:[MetadataCommand.ExtractMetadata]Using msbuild C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin as inner compiler.
[18-12-18 01:06:14.890]Info:[MetadataCommand.ExtractMetadata]Loading projects...
[18-12-18 01:06:21.325]Info:[MetadataCommand.ExtractMetadata]Generating metadata for each project...
[18-12-18 01:06:23.563]Info:[MetadataCommand]Completed Scope:MetadataCommand in 9095.811 milliseconds.
[18-12-18 01:06:23.564]Error:Error extracting metadata for C:/myprojects/myproject.csproj: Microsoft.DocAsCode.Exceptions.ExtractMetadataException: Error extracting metadata for project "C:/myprojects/myproject.csproj": System.ArgumentException: An item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at Microsoft.CodeAnalysis.SolutionState.CompilationTracker.d__30.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.CodeAnalysis.SolutionState.CompilationTracker.d__24.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.CodeAnalysis.SolutionState.CompilationTracker.d__22.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.CodeAnalysis.SolutionState.CompilationTracker.d__19.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.CodeAnalysis.SolutionState.CompilationTracker.d__32.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.CodeAnalysis.SolutionState.CompilationTracker.d__30.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.CodeAnalysis.SolutionState.CompilationTracker.d__24.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.CodeAnalysis.SolutionState.CompilationTracker.d__22.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.CodeAnalysis.SolutionState.CompilationTracker.d__19.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.RoslynProject.d__12.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.d__16.MoveNext()
at Microsoft.DocAsCode.Metadata.ManagedReference.ExtractMetadataWorker.d__16.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.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.d__11.MoveNext()
[18-12-18 01:06:23.567]Info:Completed in 9105.7346 milliseconds

The project does not have duplicate project references. The above was the only info I got using the verbose modifier. I am unable to troubleshoot without more info.

[herohua]

@rwgridstone , is it possible for you to share a minimal project that can reproduce the issue? It would help us determine the root cause and possible fix. Thanks!

[ElanHasson]

See #2532 (comment)

[superyyrrzz]

dupe of #2532