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Fix persisting null with ObservablePersistMMKV #381

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Fix persisting null with ObservablePersistMMKV #381

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6 changes: 5 additions & 1 deletion src/persist-plugins/mmkv.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,11 @@ export class ObservablePersistMMKV implements ObservablePersistPlugin {
const v = this.data[table];
if (v !== undefined) {
try {
storage.set(table, safeStringify(v));
if (v !== null) {
storage.set(table, safeStringify(v));
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@simontreny simontreny Oct 31, 2024

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On second thought, I think the root issue is how safeStringify() is implemented:

return value ? JSON.stringify(value, replacer) : value;

It means that if the value is false (false, 0, "" or null), it won't be serialized as a string. If this called JSON.stringify() directly, this would work properly as null would be serialised "null" which can be saved and restored with MMKV.

I'm not sure I understand the intent of safeStringify(), I would expect it to always return either a string or undefined.

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@simontreny simontreny Oct 31, 2024

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It probably also means that persisting 0 (or false) is broken too, as it will be persisted as a number but we will attempt to restore it with storage.getString()

} else {
storage.delete(table);
}
} catch (err) {
console.error(err);
}
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