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feat!(isObjectOf): Accept value of object with Object.assign-ed #127

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feat!(isObjectOf): Accept value of object with Object.assign-ed #127

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38480d8
test(isObjectOf): add test for value with T object assigned
lambdalisue Aug 14, 2024
4cf04b4
feat!(isObjectOf): accept any `object` with `Object.assign`
lambdalisue Aug 14, 2024
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17 changes: 8 additions & 9 deletions is/object_of.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ import {
import type { Predicate } from "../type.ts";

/**
* Return a type predicate function that returns `true` if the type of `x` is `ObjectOf<T>`.
* Return a type predicate function that returns `true` if the type of `x` is/has `ObjectOf<T>`.
*
* Use {@linkcode isRecordOf} if you want to check if the type of `x` is a record of `T`.
*
Expand All @@ -34,6 +34,12 @@ import type { Predicate } from "../type.ts";
* if (isMyType(a)) {
* const _: { a: number; b: string; c?: boolean | undefined, readonly d: string } = a;
* }
*
* // It also works for value with Object.assign
* const b: unknown = Object.assign(100, { a: 0, b: "a", d: "d" });
* if (isMyType(b)) {
* const _: { a: number; b: string; c?: boolean | undefined, readonly d: string } = b;
* }
* ```
*/
export function isObjectOf<
Expand All @@ -45,7 +51,7 @@ export function isObjectOf<
].map((k) => [k, predObj[k]]);
const pred = rewriteName(
(x): x is ObjectOf<T> => {
if (!isObject(x)) return false;
if (x == null) return false;
return preds.every(([k, pred]) => pred(x[k]));
},
"isObjectOf",
Expand All @@ -54,13 +60,6 @@ export function isObjectOf<
return annotate(pred, "predObj", predObj);
}

function isObject(x: unknown): x is Record<PropertyKey, unknown> {
if (x == null) return false;
if (typeof x !== "object" && typeof x !== "function") return false;
if (Array.isArray(x)) return false;
return true;
}

type ObjectOf<T extends Record<PropertyKey, Predicate<unknown>>> = FlatType<
// Readonly/Optional
& {
Expand Down
26 changes: 22 additions & 4 deletions is/object_of_test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -33,12 +33,30 @@ Deno.test("isObjectOf<T>", async (t) => {
true,
"Undefined properties are ignored",
);
});

await t.step("returns true on value with T object assigned", () => {
const v = { a: 0, b: "a", c: true };
// Only 'null' and 'undefined' are not Object.assign-able
assertEquals(
isObjectOf(predObj)(Object.assign("string", v)),
true,
"string",
);
assertEquals(isObjectOf(predObj)(Object.assign(100, v)), true, "number");
assertEquals(isObjectOf(predObj)(Object.assign(100n, v)), true, "bigint");
assertEquals(isObjectOf(predObj)(Object.assign(true, v)), true, "boolean");
assertEquals(isObjectOf(predObj)(Object.assign([], v)), true, "array");
assertEquals(isObjectOf(predObj)(Object.assign({}, v)), true, "object");
assertEquals(
isObjectOf(predObj)(Object.assign(() => {}, v)),
true,
"function",
);
assertEquals(
isObjectOf(predObj)(
Object.assign(() => void 0, { a: 0, b: "a", c: true }),
),
isObjectOf(predObj)(Object.assign(Symbol("symbol"), v)),
true,
"Function are treated as an object",
"symbol",
);
});

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