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Fix type narrowing for non empty array

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Eugene 2023-07-14 15:07:48 +01:00
parent 9265e9072d
commit 6d4f32287f
2 changed files with 29 additions and 10 deletions
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2
source/index.ts
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@ -384,7 +384,7 @@ is.oddInteger = isAbsoluteMod2(1);
is.emptyArray = (value: unknown): value is never[] => is.array(value) && value.length === 0;
is.nonEmptyArray = (value: unknown): value is [unknown, ...unknown[]] => is.array(value) && value.length > 0;
is.nonEmptyArray = <T = unknown>(value: T | T[]): value is [T, ...T[]] => is.array(value) && value.length > 0;
is.emptyString = (value: unknown): value is '' => is.string(value) && value.length === 0;

37
test/test.ts
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@ -1448,16 +1448,35 @@ test('is.nonEmptyArray', t => {
assert.nonEmptyArray(new Array()); // eslint-disable-line @typescript-eslint/no-array-constructor
});
// https://github.com/sindresorhus/is/issues/174
// {
// const strings = ['foo', 'bar']
// const function_ = (value: string) => value;
{
const strings = ['🦄', 'unicorn'];
const function_ = (value: string) => value;
// if (is.nonEmptyArray(strings)) {
// const value = strings[0]
// function_(value);
// }
// }
if (is.nonEmptyArray(strings)) {
const value = strings[0];
function_(value);
}
}
{
const mixed = ['🦄', 'unicorn', 1, 2];
const function_ = (value: string | number) => value;
if (is.nonEmptyArray(mixed)) {
const value = mixed[0];
function_(value);
}
}
{
const arrays = [['🦄'], ['unicorn']];
const function_ = (value: string[]) => value;
if (is.nonEmptyArray(arrays)) {
const value = arrays[0];
function_(value);
}
}
});
test('is.emptyString', t => {