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feat: pass uneval to replacer, for handling nested custom types #114

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merged 1 commit into from
Oct 15, 2025
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feat: pass uneval to replacer, for handling nested custom types #114

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5 changes: 5 additions & 0 deletions .changeset/shaggy-paths-rhyme.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'devalue': minor
---

feat: pass `uneval` to replacer, for handling nested custom types
4 changes: 2 additions & 2 deletions src/uneval.js
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Expand Up @@ -17,7 +17,7 @@ const reserved =
/**
* Turn a value into the JavaScript that creates an equivalent value
* @param {any} value
* @param {(value: any) => string | void} [replacer]
* @param {(value: any, uneval: (value: any) => string | void) => string | void} [replacer]
*/
export function uneval(value, replacer) {
const counts = new Map();
Expand All @@ -42,7 +42,7 @@ export function uneval(value, replacer) {
counts.set(thing, 1);

if (replacer) {
const str = replacer(thing);
const str = replacer(thing, (value) => uneval(value, replacer));

if (typeof str === 'string') {
custom.set(thing, str);
Expand Down
35 changes: 24 additions & 11 deletions test/test.js
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Expand Up @@ -5,7 +5,13 @@ import { uneval, unflatten, parse, stringify } from '../index.js';

globalThis.Temporal ??= (await import('@js-temporal/polyfill')).Temporal;

class Custom {
class Foo {
constructor(value) {
this.value = value;
}
}

class Bar {
constructor(value) {
this.value = value;
}
Expand Down Expand Up @@ -552,27 +558,34 @@ const fixtures = {
{
name: 'Custom type',
value: [instance, instance],
js: '(function(a){return [a,a]}(new Custom({answer:42})))',
json: '[[1,1],["Custom",2],{"answer":3},42]',
replacer: (value) => {
if (value instanceof Custom) {
return `new Custom(${uneval(value.value)})`;
js: '(function(a){return [a,a]}(new Foo({bar:new Bar({answer:42})})))',
json: '[[1,1],["Foo",2],{"bar":3},["Bar",4],{"answer":5},42]',
replacer: (value, uneval) => {
if (value instanceof Foo) {
return `new Foo(${uneval(value.value)})`;
}

if (value instanceof Bar) {
return `new Bar(${uneval(value.value)})`;
}
},
// test for https://github.com/Rich-Harris/devalue/pull/80
reducers: Object.assign(Object.create({ polluted: true }), {
Custom: (x) => x instanceof Custom && x.value
Foo: (x) => x instanceof Foo && x.value,
Bar: (x) => x instanceof Bar && x.value
}),
revivers: {
Custom: (x) => new Custom(x)
Foo: (x) => new Foo(x),
Bar: (x) => new Bar(x)
},
validate: ([obj1, obj2]) => {
assert.is(obj1, obj2);
assert.ok(obj1 instanceof Custom);
assert.equal(obj1.value.answer, 42);
assert.ok(obj1 instanceof Foo);
assert.ok(obj1.value.bar instanceof Bar);
assert.equal(obj1.value.bar.value.answer, 42);
}
}
])(new Custom({ answer: 42 }))
])(new Foo({ bar: new Bar({ answer: 42 }) }))
};

for (const [name, tests] of Object.entries(fixtures)) {
Expand Down