prefer-array-literal: Error when using Array in a type annotation

[nfriend]

Perhaps this is the intended behavior, but from the description of the rule, the prefer-array-literal rule looks like its purpose is to disallow using Array when instantiating new arrays:

new Array();
new Array(4,5);
// etc...

However, this rule also disallows using Array as a type parameter, which is one of the recommended ways of declaring Array types in the handbook:

// these throw "Replace generic-typed Array with array literal" linting error

let myArray: Array<MyObject> = [];

interface MyInterface {
    myArray: Array<number>;
}

I expected this rule to throw errors on the first set of examples above but allow the second set.

[HamletDRC]

Good find! Our coding standard says to prefer the literal syntax, even when declaring the array type.

We can add a parameter to the rule that will let you turn this on.

Why do you prefer

let myArray: Array<MyObject> = []

instead of

let myArray: MyObject[] = [];

The 2nd is shorter and gives your code base one single, consistent way to declare array types. If it were me, I would just follow the rule's advice. But that's a bit unfair because I wrote the rule :)

[nfriend]

Thanks for the response, @HamletDRC. I don't necessarily prefer the Array<> syntax, but my team's existing codebase uses it heavily. Adding an option to ignore this error when the syntax is part of a type declaration would make it much easier to integrate this rule into our project.

[ogiexela]

how can one specify the size of the array?

const foo = new Array(10)
?

[sangheestyle]

@ogiexela You can use const foo = Array(10) instead of const foo = new Array(10). The result will be the same but prefer-array-literal will be disappeared immediately.

https://stackoverflow.com/a/8205709/568901

[JoshuaKGoldberg]

Oh that sounds like a bug in the rule...

[sangheestyle]

@JoshuaKGoldberg OK. how can I help this issue?

[JoshuaKGoldberg]

That'd be great! Would you mind filing a new issue describing what you're seeing regarding being allowed to use = Array(10) but not new Array(10)? Including the normal information included with issues (version, code snippets, etc).

[sangheestyle]

@JoshuaKGoldberg Yes, I will do. I just checked which ts-lint actually does prefer-array-literal and I found it is by tslint-microsoft-contrib.

palantir/tslint#2946 (comment)

I am going to test it with up-to-date version of tslint-microsoft-contrib then I will create issue.

[sangheestyle]

@jonascarlsonschmidt Created. Thanks for guiding me.

#839