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DRAFT: display potential way to make undefined correct value for PersistedState #408

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DRAFT: display potential way to make undefined correct value for PersistedState #408

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23 changes: 14 additions & 9 deletions packages/runed/src/lib/utilities/persisted-state/persisted-state.svelte.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,16 @@ import { createSubscriber } from "svelte/reactivity";

type Serializer<T> = {
serialize: (value: T) => string;
deserialize: (value: string) => T | undefined;
deserialize: (value: string) => T;
};

type StorageType = "local" | "session";

declare const NO_VALUE: unique symbol;

// different from undefined to distinguish between deserialization failure and valid undefined value
export type NoValue = typeof NO_VALUE;

function getStorage(storageType: StorageType, window: Window & typeof globalThis): Storage {
switch (storageType) {
case "local":
Expand Down Expand Up @@ -55,11 +60,11 @@ type PersistedStateOptions<T> = {

function proxy<T>(
value: unknown,
root: T | undefined,
root: T | NoValue,
proxies: WeakMap<WeakKey, unknown>,
subscribe: VoidFunction | undefined,
update: VoidFunction | undefined,
serialize: (root?: T | undefined) => void
serialize: (root: T | NoValue) => void
): T {
if (value === null || typeof value !== "object") {
return value as T;
Expand Down Expand Up @@ -96,7 +101,7 @@ function proxy<T>(
* @see {@link https://runed.dev/docs/utilities/persisted-state}
*/
export class PersistedState<T> {
#current: T | undefined;
#current: T | NoValue;
#key: string;
#serializer: Serializer<T>;
#storage?: Storage;
Expand Down Expand Up @@ -144,7 +149,7 @@ export class PersistedState<T> {
get current(): T {
this.#subscribe?.();

let root: T | undefined;
let root: T | NoValue = NO_VALUE;
if (this.#connected) {
// when we're connected to storage, we use storage as the source of truth
const storageItem = this.#storage?.getItem(this.#key);
Expand Down Expand Up @@ -174,24 +179,24 @@ export class PersistedState<T> {
this.#update?.();
};

#deserialize(value: string): T | undefined {
#deserialize(value: string): T | NoValue {
try {
return this.#serializer.deserialize(value);
} catch (error) {
console.error(`Error when parsing "${value}" from persisted store "${this.#key}"`, error);
return;
return NO_VALUE;
}
}

#serialize(value: T | undefined): void {
#serialize(value: T | NoValue): void {
if (!this.#connected) {
// when we're not connected to storage, we only update the value in memory
this.#current = value;
return;
}

try {
if (value !== undefined) {
if (value !== NO_VALUE) {
this.#storage?.setItem(this.#key, this.#serializer.serialize(value));
}
} catch (error) {
Expand Down