feat: allow serialization/deserialization of custom data types (alternative API) by Rich-Harris · Pull Request #13149 · sveltejs/kit

Rich-Harris · 2024-12-11T19:01:24Z

Alternative to #13125, Closes #9401. Instead of separating the logic between hooks.server.js and hooks.client.js, this puts both things in hooks.js. Initially I thought the separate made more sense, but I'm not so sure. In essentially all cases, you'll need a reference to the custom type — for an instanceof check during serialization, and for instantiation during deserialization — so there doesn't really seem to be a benefit to keeping them in separate files.

Putting them in one place is easier to understand, and means you can't end up with mismatches. It does mean that the serialization logic ends up in the client, but we're talking about a few bytes for a value instanceof Foo && [value.blah] function.

I'm not too sure about the naming of things. Right now it looks like this:

// hooks.js
import { MyCustomThing } from '$lib/stuff';

export const transport = {
  MyCustomThing: {
    encode: (value) => value instanceof MyCustomThing && [value.blah],
    decode: ([blah]) => new MyCustomThing(blah)
  }
};

TODO:

add a type for the export (ultimately, this should be added automatically just like other hooks)
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Co-authored-by: Rich Harris <richard.a.harris@gmail.com>

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packages/kit/src/core/sync/write_client_manifest.js

…:sveltejs/kit into serialize-deserialize-non-pojo-universal

Rich-Harris · 2024-12-11T19:49:49Z

preview: https://svelte-dev-git-preview-kit-13149-svelte.vercel.app/

this is an automated message

benmccann · 2024-12-11T20:58:56Z

I would prefer a version where you can tree-shake the server code:

export const transportEncode = {
  MyCustomThing: (value) => value instanceof MyCustomThing && [value.blah]
};

export const transportDecode = {
  MyCustomThing: ([blah]) => new MyCustomThing(blah)
};

Rich-Harris · 2024-12-11T21:09:40Z

We're talking about a few bytes, unless you have a realistic example to the contrary? I don't think the trade-off is a good one

dummdidumm · 2024-12-12T14:15:30Z

packages/kit/src/exports/public.d.ts

+ * ```
+ * @since 2.11.0
+ */
+export type Transport = Record<string, Transporter>;


How much use will people really make of this specific type, since it's not helping much with type safety? Should we just omit it?

I still think we should at least offer the defineTransport function for type safety. We can call it something else if we don't like it but it would be nice

It's helping plenty — it might not be able to provide inference for the decode parameter, but it enforces the correct shape of transport (i.e. you can't omit either encode or decode for a given transporter, and you can't misspell them). And exposing Transporter means you can add the missing type safety yourself:

export const transport: Transport = { Foo: { encode: (value) => ..., decode: (data) => ... } satisfies Transporter<Foo, [blah]> };

We could always add defineTransport later if we feel like we need to, but I don't think we should break with existing conventions just yet.

@dummdidumm can we add this to 0 effort typesafe?

Yes and no - we can add satisfies Transport for the top level, but we can't do much for the individual entries

AlbertMarashi · 2024-12-14T18:16:08Z

Amazing stuff!

trueadm and others added 22 commits December 9, 2024 12:40

feat: allow serialization/deserialization of custom data types

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feat: allow serialization/deserialization of custom data types

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feat: allow serialization/deserialization of custom data types

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feat: allow serialization/deserialization of custom data types

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feat: allow serialization/deserialization of custom data types

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Merge branch 'main' into serialize-deserialize-non-pojo

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Update packages/kit/src/core/sync/write_client_manifest.js

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Co-authored-by: Rich Harris <richard.a.harris@gmail.com>

use universal transport hook

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fix

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Rich-Harris commented Dec 11, 2024

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Rich-Harris and others added 3 commits December 11, 2024 14:14

Update packages/kit/src/core/sync/write_client_manifest.js

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Merge branch 'serialize-deserialize-non-pojo-universal' of github.com…

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…:sveltejs/kit into serialize-deserialize-non-pojo-universal

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add types, rename to encode/decode

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Rich-Harris added 3 commits December 11, 2024 14:57

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Rich-Harris mentioned this pull request Dec 11, 2024

feat: allow serialization/deserialization of custom data types #13125

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dummdidumm reviewed Dec 12, 2024

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Rich-Harris merged commit 3d9e03a into main Dec 12, 2024

Rich-Harris deleted the serialize-deserialize-non-pojo-universal branch December 12, 2024 14:47

github-actions bot mentioned this pull request Dec 12, 2024

Version Packages #13147

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dummdidumm mentioned this pull request Dec 12, 2024

Allow the serialisation/deserialisation of non-POJOs #9401

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Rich-Harris mentioned this pull request Dec 12, 2024

Ability to serialize arbitrary classes to send to client #8743

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shyakadavis mentioned this pull request Dec 13, 2024

Provide reducers/reviviers for devalue in superForm/superValidate functions ciscoheat/sveltekit-superforms#423

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cooolbros mentioned this pull request Dec 14, 2024

Split client and server transporters #13158

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gurpreetatwal mentioned this pull request Apr 4, 2025

Introduce of custom transports leads to deserialize not working on server side #13675

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teemingc mentioned this pull request Aug 19, 2025

When streaming a promise from load that returns an object requiring serialization through transport. Uncaught ReferenceError: app is not defined ocurs #13428

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feat: allow serialization/deserialization of custom data types (alternative API)#13149

feat: allow serialization/deserialization of custom data types (alternative API)#13149
Rich-Harris merged 30 commits intomainfrom
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