Allow configuration of missing property quickfix

Search Terms

property does not exist quickfix
quick fix
create private property
quickfix configuration

Suggestion

When referencing a property that doesn't exist within a class, you get the error Property 'foo' does not exist on type 'MyClass'.ts(2339). In VS Code you can then do cmd-. to get the quickfix option Declare property 'foo'. When you select this, a property is declared, but it is created with default visibility.

Based on digging in to the code here:

https://github.com/microsoft/TypeScript/blob/15daf42b2c0bc4f06970c9e4688f1a93bff0f7a0/src/services/codefixes/fixAddMissingMember.ts#L204-L210
it doesn't look like there's anyway to configure this.

It would be really nice if there was a way to configure the quickfix functionality to default to creating properties with a given access modifier (in my case I'd like to default them to private). Given the upcoming #field private-named fields stuff, it seems like this could also be a useful way to let people decide what they want to use.

Use Cases

I would like to have the properties created by quickfix all start as private, to encourage writing classes with strong encapsulation.
The current approach requires me to go back and modify the generated declaration every time.

Examples

Starting code with missing property:

export class MyClass {
  public constructor(foo: number) {
    this.foo = foo;
  }
}

After applying the quickfix to the line this.foo = foo; it becomes:

export class MyClass {

  foo: number;

  public constructor(foo: number) {
    this.foo = foo;
  }
}

but I would like some way to configure it to instead do:

export class MyClass {

  private foo: number;

  public constructor(foo: number) {
    this.foo = foo;
  }
}

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.

Start with src/services/codefixes/fixAddMissingMember.ts around lines 204-210, the implementation identified in the issue. Determine where the missing-member quickfix chooses the property's visibility and how a configuration option could control it, including the private-field use case. Done means the quickfix can be configured to generate a private property while preserving the existing default behavior.