NullReferenceException after upgrading from 1.2.1 -> 2.3.1

[JohanLarsson]

Version 2.3.1:

Steps to Reproduce:

1. Clone https://github.com/DotNetAnalyzers/PropertyChangedAnalyzers/tree/8d5fc945d8a879214f76e38e8b53111397547505
2. Run tests

Expected Behavior:

All tests passed when using 1.2.1

Actual Behavior:

System.NullReferenceException : Object reference not set to an instance of an object.
at Microsoft.CodeAnalysis.CodeFixes.BatchFixAllProvider.<TryAddDocumentMergeChangesAsync>d__19.MoveNext()

Debugged it and oldSolution.Workspace.Services.GetService<IDocumentTextDifferencingService>() returns null now. http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/CodeFixes/FixAllOccurrences/BatchFixAllProvider.cs,320

Not unlikely that something is wrong in the test fixture but something changed between versions.

[Pilchie]

How is your Workspace constructed in tests?

[JeremyTCD]

I have the same issue with 2.4.0. I'm using the default AdhocWorkspace constructor to instantiate a Workspace instance to test batch fixes for my diagnostic analyzers:

roslyn/src/Workspaces/Core/Portable/Workspace/AdhocWorkspace.cs

Lines 23 to 26 in ab56a4a

	public AdhocWorkspace()
	: this(Host.Mef.MefHostServices.DefaultHost)
	{
	}

BatchFixAllProvider attempts to retrieve an IDocumentTextDifferencingService from the workspace but is unable to find one. As mentioned by @JohanLarsson, the following GetService invocation returns null:

roslyn/src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/BatchFixAllProvider.cs

Line 319 in ab56a4a

var differenceService = oldSolution.Workspace.Services.GetService<IDocumentTextDifferencingService>();

Changing the line to the following allows tests to run normally:

var differenceService = oldSolution.Workspace.Services.GetService<IDocumentTextDifferencingService>() ?? new DefaultDocumentTextDifferencingService();

I'm not completely certain, but it appears that if a workspace has no IDocumentTextDifferencingService then defaulting to DefaultDocumentTextDifferencingService is acceptable.

[ThyPillow]

I have the same issue with 2.6.1.
I'm using a MSBuildWorkspace to apply several identified code fixes on all projects of a solution, this relates to #2020 as this is exactly what I am doing.

As long as there's only one Diagnostic provided, the code fix is being applied with no error, but as soon as the BatchFixAllProvider is trying to merge several of them, the NullReferenceException is thrown.

It seems the LinkedFileDiffMergingSession already has the behavior described by @JeremyTCD

roslyn/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs

Line 89 in 542daef

var textDifferencingService = _oldSolution.Workspace.Services.GetService<IDocumentTextDifferencingService>() ?? new DefaultDocumentTextDifferencingService();

If you are okay with this proposed behavior I can submit the PR to fix it.

[ThyPillow]

This has been fixed by #23492

[CyrusNajmabadi]

This was fixed. CLosing out.