String Literal refactoring support

[basarat]

Thanks for #5185 🌹. Would be great if we could get refactoring support for string literals

type Foo = "aReallyLong" | "bReallyLong"; // allow me to rename any of these values
let foo:Foo;
foo = "aReallyLong"; // allow me to rename this value

refs #5554 (comment)

[falsandtru]

+1

[mhegazy]

PRs are welcomed.

The change should be done in services.ts::getReferencedSymbolsForNode. String literals do not have a symbol, so we will need to check their contextual type, and if it is a string literal type, replace all strings with the same contextual type.

[DanielRosenwasser]

so we will need to check their contextual type

This will require a breaking change in the type checker API because right now the exposed getContextualType returns the apparent type.

[mhegazy]

ah. we can add another one, to return the string literal type at a location then.

[DanielRosenwasser]

I think we should just do the correct thing and make the break. I don't think most people will be affected by it, and It's going to be necessary elsewhere. We should favor a more general solution that gets users where they need to be than one that solves a specific use-case. I'll make the change and see what breaks in our language service.

[ZSkycat]

another case:

interface TestA {
    'propA': number;
}

type TestAKey = keyof TestA;

function FnA<K extends TestAKey>(type: K, val: TestA[K]) {}

FnA('propA', 0);

Support for renaming refactoring will be useful for functions like addEventListener.

[Duckers]

Bump. Perhaps this wasn't that urgent in 2015 when filed, but now with the level of sophistication TS has reached I think this should be reconsidered for roadmap.

Whether this feature exists or not is a pretty big deal wrt. what should be considered best practice for enums when writing new code/new APIs.

String literals have benefits over enums as they require no imports to be used, is easy to debug and serialize, and makes for less verbose code. Also a critical tool for javascript interop where there are no pre-existing enum objects.

Without refactoring support, committing to string literals as best practice for how we design APIs in TypeScript is sketchy.

[Niryo]

I don't get something...It looks like Intellij IDE can do exactly what we ask for in this Issue. How the hell Intellij can do this if it's not supported in Typescript itself?

[fuafa]

Maybe IntelliJ implements their own language service?

[Niryo]

I don't know...Maybe typescript already supports this and it's now an issue with VScode? What about this merged commit #5615, did it solve the issue?

[aspirisen]

That would be very handy to have such feature in TypeScript

[dontsave]

Bump. This should be a feature in TypeScript and VSCode in 2020. Right now to get refactoring behavior in VSCode you have no choice but to use string enums, which are far less elegant

[theluk]

mega bump

[Kingwl]

I'd like to take a try on this.