Provide a quick fix for uninitalized class properties

class Point {
    z: string;
    constructor() {
    }
}

We should provide a quick fix here to provide a definite assignment assertion on z under --strictPropertyInitialization. Bonus points if we only provide the quick fix when the property has actually been written to!

I am assuming we will provide 3 actions:

Add definite assignment operator (assuming it was written to at least once in the class)
Add an initialization in the constructor (assuming we can initialize it, e.g. string, number, or a type that has a constructor)
Add | undefined to the type declaration

I'd like to work on this 😃

Go for it!

Add definite assignment operator (assuming it was written to at least once in the class)
Add an initialization in the constructor (assuming we can initialize it, e.g. string, number, or a type that has a constructor)

How should we set their initializer expression?

something like https://github.com/Microsoft/TypeScript/blob/master/src/services/codefixes/fixAddMissingMember.ts#L105

first there has to be a constructor. I would ignore the case where there is no constructor at the moment.

Mohamed Hegazy (@mhegazy)

ping Mohamed Hegazy (@mhegazy)
I'm not sure I understand your meaning correctly

for example:
https://www.typescriptlang.org/play/index.html#src=class%20TT%20%7B%0D%0A%7D%0D%0A%0D%0Aclass%20T%20%7B%0D%0A%20%20%20%20c%3A%20number%3B%0D%0A%20%20%20%20b%3A%20TT%3B%0D%0A%20%20%20%20a%3A%20string%3B%0D%0A%7D%0D%0A

class TT {
}

class T {
    c: number;
    b: TT;
    a: string;
}

what should class T props do after codefix?

class T {
    c: number | undefined = undefined;
    b: TT | undefined = undefined;
    a: string | undefined = undefined;
}

or

class T {
    c: number = 0;
    b: TT = new TT();
    a: string = "";
}

or other way?

you do not need the = undefined.

I think we should have 3 code actions:

add | undefined

class T {
    c: number | undefined ;
    b: TT | undefined ;
    a: string | undefined;
}

add an intializer

class T {
    c: number = 0 ;
    b: TT;
    a: string = "";
}

or 3. add a definite assignment operator

class T {
    c!: number;
    b!: TT;
    a!: string;
}

thanks for your response

and if the TT has the constructor

class TT {
    constructor () {}
}

then should i create a instance of TT in the prop b?


class T {
    c: number = 0 ;
    b: TT = new TT(); // this
    a: string = "";
}

then should i create a instance of TT in the prop b?

Sounds reasonable

i have finished codefix work 😄
review required

Nice! Instead of "Add 'undefined' type to property '{0}'", did you consider making the property optional via, e.g., prop?: string;?

We recently (probably with 2.7's --strictPropertyInitialization) discovered a problem where we thought we had declared an optional property:

  c: () => number | undefined;

But that's actually:

  c: () => (number | undefined);

And that's harder to "back-into" had we just used this syntax from the get-go:

  c?: () => number;

Oleg Vaskevich (@vaskevich)

Oleg Vaskevich (@vaskevich) SlurpTheo I'd recommend filing a new issue; if a lot of users end up requesting that, we can consider it.

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Provide a quick fix for uninitalized class properties #21509

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Provide a quick fix for uninitalized class properties #21509

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mhegazy commented on Jan 31, 2018

Kingwl commented on Feb 1, 2018

mhegazy commented on Feb 1, 2018

Kingwl commented on Feb 1, 2018

mhegazy commented on Feb 1, 2018

Kingwl commented on Feb 2, 2018

mhegazy commented on Feb 2, 2018

Kingwl commented on Feb 2, 2018

mhegazy commented on Feb 2, 2018

Kingwl commented on Feb 2, 2018

vaskevich commented on Mar 8, 2018

SlurpTheo commented on Mar 16, 2018

DanielRosenwasser commented on Mar 26, 2018

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