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Typescript 3.8.3 : Sharp notation for private method must be alloweded #37677
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Activity
- Reacted by David Gonçalves, ProPuke, Justin Kunz and MarlonPerez-01
i think their is not private method in your example. try to write #greet() to replace greet() method in your example, and you have this error message : "A method cannot be named with a private identifier.(18022)".
Reacted by Jesús Leganés-Combarro, Jeremy Black, inker, Wojciech Gebczyk, Jimmy Wärting, Sachin Hegde, Hayden, Mark LeMerise and DmitriiTrue yeah, and I can't seem to find another issue about this 👍
The relevant proposal for private methods is here: https://github.com/tc39/proposal-private-methods
Private methods are only shipping in XS so far, but they are in active development in V8.
In the same way, static private attribute in class must be allowed too.
however :class Test { static #TEST:any; }do :
TS18019: 'static' modifier cannot be used with a private identifier
Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chromeReacted by Ruslan Gilmullin, Miquel, vfsfitvnm, Artemii, Chris Blake and Tony SamperiIn the same way, static private attribute in class must be allowed too.
however :class Test { static #TEST:any; }do :
TS18019: 'static' modifier cannot be used with a private identifier
Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chromeThis is a problem...
class S { static #instance: S; static getInstance(): S { if (!this.#instance) { this.#instance = new S(); } return this.#instance; } }
How can I perform this?
Thank you a lot in advance
In the same way, static private attribute in class must be allowed too.
however :class Test { static #TEST:any; }do :
TS18019: 'static' modifier cannot be used with a private identifier
Référence : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_fields
proposal : https://github.com/tc39/proposal-static-class-features
Already compatible in edge (79), node (13), chromeThis is a problem...
class S { static #instance: S; static getInstance(): S { if (!this.#instance) { this.#instance = new S(); } return this.#instance; } }
How can I perform this?
Thank you a lot in advance
Private properties and methods should not be accessible from outside the class instance.
Own methods of a class should have access to private methods of a class if they are static or not.Can be a constructor private? If it's not, is this singleton example valid?
#instanceis a private and static field insideSclass andgetInstanceis static too. As you can create this kind of static fields and methods in NodeJS, it should work in TShttps://node.green/#ESNEXT-candidate--stage-3--static-class-fields-private-static-class-fields
Node allow this way for creating singleton patterns. Try out yourself. I don't understand why TS is showing that error.
It was a misunderstanding. I thought that your problem was the 'inaccessibility' of the private field
#instancefrom the not private methodgetInstance(). I agree that there should be no problem.Anyway. That's the point to use this pattern? Anyone can instantiate this class with
newoperator. How can I prevent this or it should be a convention in a team not to usenewoperator with this class?That's a good point. I think we can use a private constructor. I think It fits well with this pattern. But, in a singleton pattern everyone can use getInstance method or new. If getInstance method exists, then should be used
I'm also unable to use private getters and setters in a class in TS.
class GSExample { #a: number = 0; get a() { // this is file return this.#a; } set a(value: number) { // this is file this.#a = value; } get #b() { // Error: An accessor cannot be named with a private identifier.(18023) return this.a * 2; } set #b(value: number) { // Error: An accessor cannot be named with a private identifier.(18023) this.a = value / 2; } }
Reacted by Natanael Russo10 remaining items
Yes, but I guess it leads to
#isEmptybeing assigned to each instance instead of being assigned to the class prototype like other methods.Reacted by Boaris, Binau, Miquel, Quentin Roy, Daniel, Hayden and Andrey PonomarevOrta Therox (@orta) is it really in discussion? It is a spec compliance issue now.
Reacted by Art, Frank Wienberg, David, Gabriel Saillard, Wojciech Gebczyk, Daniel, David Gilbertson, Andrey Ponomarev, Zach Wegrzyniak and Justin KunzAlso, the workaround leads to the class having field initializers.
While this is not a bad thing per se, it adds an extra constraint on constructor code: If a class has field initializers, its constructor must callsuper()as the first statement. If there are no field initializers, the only limitation for statements before the super constructor call is that they may not usethis, which is less restrictive.One more annoying thing with the workaround: Forward references do not work.
It should be possible to initialize a private field with a call to a private method. But since with the workaround, TypeScript treats the #private method like a field with an initializer, this only works if the private method is declared before the field using it.Works in ECMAScript:
class Test { #myField = this.#init(3); #init(x) { return x + 1; } }Error ("Property '#init' is used before its declaration") when trying to represent this with the workaround in TypeScript, and also a run-time error in ECMAScript when trying to instantiate that class ("TypeError: Cannot read private member #init from an object whose class did not declare it"):
class Test { #myField = this.#init(3); #init = (x) => { return x + 1; } }This means you are forced to define helper methods before fields, which might not be one's favorite code style.
Considering all the downsides, in our project, we switched back to (clumsy) symbols / "soft" private members. But we are still eagerly waiting for TypeScript to support #private members and would immediately adapt our code!
Is there any reason why it is not allowed to use private methods in Typescript?
Reacted by Gabriel Saillard, Daniel and Justin KunzIs there any reason why it is not allowed to use private methods in Typescript?
Good question. Especially when you use TSC only for type checking and do the actual compilation with Babel, apart from the error message TS18022, everything seems to work fine.
I just give the approach a go to use ts-ignore when declaring #private methods. Ugly, but still better than Symbols. All code just using such methods works fine and is correctly type-checked without any ts-ignore.
Could we probably please have a compiler flag to suppress TS18022?Could we probably please have a compiler flag to suppress TS18022?
That doesn't make any sense... This is a spec compliance issue and should just be fixed.
Reacted by Gabriel Saillard, Wojciech Gebczyk, Daniel and Justin KunzYet another issue is setting private identifiers via a class constructor:
class Testing { constructor(private #test: string) {} // ERROR: Private identifiers cannot be used as parameters }
Reacted by Frank Wienberg, Lauren Yim, Wojciech Gebczyk, flasheye12, André Posso, André Abreu, Eren ÇAY, regnaio, Christopher Addison, Artem and 3 moreCould we probably please have a compiler flag to suppress TS18022?
That doesn't make any sense... This is a spec compliance issue and should just be fixed.
Of course I would prefer a fix, too!
I just guess it is much more effort to implement code generation for that feature, and we only need the type checking part. So for the time being, we use ts-ignore as a workaround, so my real issue with that workaround is that it is still not possible to ignore a specific error.Is this issue being addressed in the current roadmap? If not, has this issue been triaged at least?
Please give us an update of some sorts.
ThanksReacted by Frank Wienberg, Andres Rodriguez, Jeremy Black, Tiago Almeida, Alexandre Villeneuve, Tomáš Polomský, Håkon Ellingsen, Tomas Chmelevskij, Frits Talbot, Daniel and 4 moreGood news here: #39066 (comment)
Pls fix this soon, I don't use typescript but a ts linter and babel ts compilation and it sucks to have red lines everywhere while my code runs perfectly fine.
I'm looking forward to fix, it's horrible microsoft/vscode#106351
Implemented in #42458
Reacted by Angelo and Lucio Martinez
Search Terms
TS18022, sharp
Suggestion
Sharp notation for private method must be alloweded : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Private_instance_methods
Use Cases
class Test {
#test() {}
}
Examples
class Test {
#test() {}
}
=> TS18022: A method cannot be named with a private identifier.
Checklist
My suggestion meets these guidelines: