Like this! Can we instead put property on option declaration instead. Eg look at affectsSemanticDiagnostics in CommandLineOptionBase

Also noUnusedLabels shouldnt need the new sourceFile. Instead it needs to set affectsSemanticDiagnostics

It already had affectsSemanticDiagnostics, the problem is that the --noUnusedLabels error is attached to the SourceFile#bindDiagnostics directly during binding. While affectsSemanticDiagnostics seems to only affect semanticDiagnosticsPerFile.

Why ? RootDir and paths shouldn't affect syntaxTree or bindDiagnostics?
Same goes for lib, baseUrl, typeRoots, paths

Those all effect module resolution, and SourceFile stores resolvedModules.

Also want to check if: getStrictOptionValue(opts, "alwaysStrict") (which depends on value of strict and alwaysStrict flag)

Handled this by adding affectsSourceFile to both "alwaysStrict" and "strict".

I don't think you need to create separate objects just for comparison, You should just iterate through options and achieve same thing.. Eg. compilerOptionsAffectSemanticDiagnostics

While you have added this, could you please change changesAffectModuleResolution as well to use this instead of manual checks.

👍

Btw you have option.type to determine if you want to do arrayIsEqualTo or equalOwnProperties or just direct equals check.

Here's how far I got:

export function areCompilerOptionsEqual(option: CommandLineOption, a: unknown, b: unknown) {
    switch (option.type) {
        case "boolean":
        case "number":
        case "string":
            return a === b;
        case "list":
            return arraysEqual(a as unknown[], b as unknown[], (aa, bb) => areCompilerOptionsEqual((option as CommandLineOptionOfListType).element, aa, bb));
        case "object":
            return equalOwnProperties(a as MapLike<unknown>, b as MapLike<unknown>, isJsonEqual);
        default:
            something with maps;
    }
}

Doesn't seem worth it since I need to call isJsonEqual in the nested case anyway, and I need some casts which might not be valid if someone put a wrong value in their tsconfig.

I think this change is correct? rootDir doesn't affect module resolution, it affects emit.