Compile classes fields marked as "private" to ECMAScript private fields (#xxx)

[TokugawaTakeshi]

Search Terms

TypeScript pivate fields, ECMAScript private fields

Suggestion

Compile classes fields marked as "private" to ECMAScript private fields (#xxx).

In TypeScript 3.8, ECMAScript private fields has been added, but TypeScript class fields marked as "private" are sill being compiled to default public ECMAScript-fields.

Problem 1: The developers forced to rewrite their code to new syntax

Because ECMAScript private fields are more safe, developer forced to rewrite "private"-marked class fields to ECMAScript class fields.

Problem 2: Syntax unity loss

class Application {
  
  public examplePublicField1: string;
  public examplePublicField2: string;

  #examplePrivateField: string; // standing out and annoying
}

Well, even if I stop to use public keyword, still protected keyword exists:

class Application {

  examplePublicField: string;
  
  protected exampleProtectedClassField: string; // standing out and annoying

  #examplePrivateField: string;
}

Solution alternative 1

Compile private examplePrivateClassField to #examplePrivateClassField when TypeScript compiler's target option is ES2020. Otherwise compile private examplePrivateClassField to default public examplePrivateClassField.

Solution Alternative 2

Add compiler option like unifiedPrivate which provides above behavior when turned on.

Examples

class Application {
    private privateClassField: stirng;
}

should be compiled to:

class Application {
   constructor(example) {
        this.#example = example;
    }
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[nmain]

Open discussion in #31670, including rationale for why this would not be done

[RyanCavanaugh]

Per above 👆 we won't be doing this

[TokugawaTakeshi]

You have raised the holy war between private keyword followers and and ECMAScript private field followers 🙂 The mental energy consumption for the team work will increase 😕