Roslyn: IOperation - don't understand the end-to-end story

[ljw1004]

I recently wrote an analyzer that used IOperation. It was easy enough to make it work correctly, but I don't understand any of the ramifications. I'd love some guidance from the Roslyn team about the end-to-end story.

// (Step 1) Write the analyzer with a dependency on NuGet package Microsoft.CodeAnalysis v2.1.0
public override void Initialize(AnalysisContext context) {
  context.RegisterOperationAction(AnalyzeAwaitOperation, OperationKind.AwaitExpression);
}

// (Step 2) Edit the csproj of a project that *uses* my analyzer:
<Project ...>
  <PropertyGroup>
    <Features>IOperation</Features>
    ...

My overall question is: I am writing an analyzer with target audience XYZ. Can I reasonable use IOperation to write my analyzer?

I know how to answer that question if XYZ is solely myself :) but don't know what the answer is for all other possible audiences. Here are some of the dead-ends I researched trying to figure out the answer...

Q1. I understand that this msbuild Features flag translates into the csc.exe flag /features:IOperation, but I only got this by digging through the Roslyn reference source. This command-line argument doesn't seem to be listed on any of the public docs about CSC command line arguments. Should it be?

Q2. What happens if someone does /features:IOperation in a version of C# that doesn't support it? What happens when you do it in C#5? C#6?

Q3. If I write an analyzer that uses IOperation, presumably there's a minimum Microsoft.CodeAnalysis NuGet version that I must reference. Is that minimum 2.1.0?

Q4. What happens if I invoke csc.exe /a:MyAnalyzer.dll when MyAnalyzer depends on a version of Microsoft.CodeAnalysis NuGet package that's newer than what csc.exe supports?

Q5. Based on Q3 and Q4, are there any versions of csc.exe where its DLL version-checks allow me to /a:MyIOperationAnalyzer.dll but where it doesn't support /feature:IOperation ?

Q6. Is IOperation still considered an experimental feature that shouldn't be used for proper productionized analyzers?

[ljw1004]

:)

[jmarolf]

My understanding is that IOperstion is an experimental feature that will undergo breaking changes between now and when it reaches RTM.

[dropsonic]

Any updates? What will happen if I use this feature in v1.3.2?

[sharwell]

@mavasani Can you reply with the first version of Roslyn where IOperation is stable and see if this can be closed? I can't figure it out due to #29649 and #29650.

[mavasani]

2.6.1 is the recommended minimum version with first fully supported IOperation release.