Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Improvment to Array.isArray #151

Open
wants to merge 5 commits into
base: main
Choose a base branch
from
Open

Improvment to Array.isArray #151

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
ab9d475
Fixes to isArray
Mickemouse0 Jun 17, 2023
d2918bb
Update is-array.d.ts
Mickemouse0 Jun 17, 2023
710e603
Improve readability
Mickemouse0 Jun 20, 2023
db19046
Fix indentation
Mickemouse0 Jun 20, 2023
4be3b4f
Remove invalid test
Mickemouse0 Jun 23, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion src/entrypoints/is-array.d.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
interface ArrayConstructor {
isArray(arg: any): arg is unknown[];
isArray<T>(arg: true extends TSReset.IsAny<T> ? never : T): arg is true extends TSReset.IsAny<T> ? never : T extends ReadonlyArray<unknown> ? T : Array<T> extends T ? Array<T> : never;
}
Comment on lines 1 to 3
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Not sure I agree with the decision to disallow any, since narrowing a value from any to unknown[] seems like a valid thing to want to do.

Setting that aside, here's another way you could accomplish the same thing:

Suggested change
interface ArrayConstructor {
isArray(arg: any): arg is unknown[];
isArray<T>(arg: true extends TSReset.IsAny<T> ? never : T): arg is true extends TSReset.IsAny<T> ? never : T extends ReadonlyArray<unknown> ? T : Array<T> extends T ? Array<T> : never;
}
interface ArrayConstructor {
isArray<T>(arg: NotAny<T>): arg is Extract<NotAny<T>, readonly unknown[]>;
}
type NotAny<T> = 0 extends 1 & T ? never : T

3 changes: 3 additions & 0 deletions src/entrypoints/utils.d.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,4 +14,7 @@ declare namespace TSReset {
: T extends symbol
? symbol
: T;

// https://stackoverflow.com/questions/49927523/disallow-call-with-any/49928360#49928360
type IsAny<T> = 0 extends 1 & T ? true : false;
}
82 changes: 81 additions & 1 deletion src/tests/is-array.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,30 @@ doNotExecute(() => {
}
});

doNotExecute(() => {
const maybeArr = [1, 2, 3] as unknown[];

if (Array.isArray(maybeArr)) {
type tests = [Expect<Equal<typeof maybeArr, unknown[]>>];
}
});

doNotExecute(() => {
const maybeArr = [1, 2, 3] as any;

if (Array.isArray(maybeArr)) {
type tests = [Expect<Equal<typeof maybeArr, any[]>>];
}
});

doNotExecute(() => {
const maybeArr = [1, 2, 3] as any[];

if (Array.isArray(maybeArr)) {
type tests = [Expect<Equal<typeof maybeArr, any[]>>];
}
});

doNotExecute(() => {
const arrOrString = [] as string[] | string;

Expand All @@ -17,9 +41,65 @@ doNotExecute(() => {
});

doNotExecute(() => {
let path: string | string[] = [];
const arrOrString = [] as readonly string[] | string;

if (Array.isArray(arrOrString)) {
type tests = [Expect<Equal<typeof arrOrString, readonly string[]>>];
}
});

doNotExecute(() => {
const arrOrString = [] as readonly string[] | string[] | string;

if (Array.isArray(arrOrString)) {
type tests = [Expect<Equal<typeof arrOrString, readonly string[] | string[]>>];
}
});

doNotExecute(() => {
const arrOrString = [] as string[] | string;

if (Array.isArray(arrOrString)) return;
type tests = [Expect<Equal<typeof arrOrString, string>>];
});

doNotExecute(() => {
const arrOrString = [] as readonly string[] | string;

if (Array.isArray(arrOrString)) return;
type tests = [Expect<Equal<typeof arrOrString, string>>];
});

doNotExecute(() => {
const arrOrString = [] as readonly string[] | string[] | string;

if (Array.isArray(arrOrString)) return;
type tests = [Expect<Equal<typeof arrOrString, string>>];
});

doNotExecute(() => {
let arrOrString = "" as string | [1, 2];

if (Array.isArray(arrOrString)) {
type tests = [Expect<Equal<typeof arrOrString, [1, 2]>>];
}
});

doNotExecute(() => {
let path = [] as string | string[];

const paths = Array.isArray(path) ? path : [path];

type tests = [Expect<Equal<typeof paths, string[]>>];
});

doNotExecute(() => {
function test<T>(value: T) {
type Unarray<T> = T extends Array<infer U> ? U : T;
const inner = <X extends Unarray<T>>(v: X[]) => {};

if (Array.isArray(value)) {
inner(value);
}
}
});