How to properly rename a variable from a code-fix

[Evangelink]

When trying to implement some analyzer code-fix for rule RS0046 - Avoid 'opt' suffix which renames a variable, I have tried to use the LookupSymbols API to avoid name clash but I am facing a couple of issues:

Name clash for method parameters.

Consider the following method

public class C
{
    public void M(string? sOpt, string s, TextSpan? selectionOpt) // Rule correctly flags 'sOpt' and 'selectionOpt' but codefix shall not be offered as they result in name clash
    {
        if (selectionOpt.HasValue)
        {
            var selection = selectionOpt.Value;
            Console.WriteLine(selection);
        }
    }
}

but I do not want to register a code-fix which renames sOpt into s and selectionOpt into selection because it will cause a name clash.

Doing some experiments around the SemanticModel.LookupSymbols API, I have managed to detect the sOpt case by passing a position in the method block (last statement span end) but from this position I cannot detect the variable selection which is now out-of-scope. The only thing I can think of is to collect all symbols but that seems rather inefficient and I assume there are lots of analyzers/code-fix in a similar situation.

On dotnet/roslyn-analyzers#3813, @sharwell recommended to have a look at roslyn's name suggestion completion provider, which I guess is https://github.com/dotnet/roslyn/blob/master/src/Features/CSharp/Portable/Completion/CompletionProviders/DeclarationNameCompletionProvider.cs but I couldn't really find which part needs to be used.

Rename all references

I am currently using the Renamer.RenameSymbolAsync API to rename the variable but I have noticed that if I rename an interface or base class parameter name, the implementations are not renamed. Is there a way to rename in chain?

Thank you for the help!

[sharwell]

The entry point to code to generate a name, accounting for other names in scope, is here:

roslyn/src/Features/CSharp/Portable/Completion/CompletionProviders/DeclarationNameCompletionProvider.cs

Lines 250 to 257 in 41fa23e

	var uniqueName = semanticFactsService.GenerateUniqueName(
	context.SemanticModel,
	context.TargetToken.Parent,
	containerOpt: null,
	baseName: name,
	filter: s => IsRelevantSymbolKind(s),
	usedNames: Enumerable.Empty<string>(),
	cancellationToken: cancellationToken);

[Evangelink]

@sharwell Thanks for the pointer, regarding GetLanguageService<ISemanticFactsService> it seems that we need to reference the workspace package which isn't available in roslyn-analyzers, is it ok or is it going to cause runtime issues?

[sharwell]

You'll need to copy all of the implementation necessary for that feature over to roslyn-analyzers.