Add an `sdkVersionConstraint` getter to `WorkspacePackage`

[pq]

See discussion in https://dart-review.googlesource.com/c/sdk/+/335063/3/pkg/analysis_server/lib/src/services/user_prompts/dart_fix_prompt_manager.dart.

[bwilkerson]

Let me summarize where I think that conversation landed. Let me know if I've misunderstood.

We're moving from AnalysisContext.analysisOptions to AnalysisContext.getAnalysisOptionsForFile (though we might want to consider dropping the get in the process). That is, the API will allow different files within an analysis context to have different analysis options.

We're moving from AnalysisContext.analysisOptions.sdkVersionConstraint to AnalysisContext.contextRoot.workspace.findPackageFor.sdkVersionConstraint. That is, the SDK constraints will be the same for everything within a package, but can be different from package to package within an analysis context.

We're postponing the decision about whether to wrap these values in an internal object for convenience and safety until we've had a change to understand what the impact would actually be.

[pq]

That sounds right. Does it follow thatWorkspace will get a new sdkVersionConstraint property and it will be up to the concrete workspace types (Blaze, Gn, Pub, etc) to implement it?

[scheglov]

Do you mean WorkspacePackage, not Workspace?

[bwilkerson]

Yes, the proposal is that there will be a new WorkspacePackage.sdkVersionConstraint getter.

[bwilkerson]

@keertip For visibility.

[pq]

@keertip: I was possibly going to take a look at this (unless you want to?)

[keertip]

@pq, that's fine by me, have not had the cycles to start on this as yet.