Add wasm32 support to the rust sdk by thlsrms · Pull Request #2704 · clockworklabs/SpacetimeDB

thlsrms · 2025-05-05T23:28:22Z

Description of Changes

Enabled the Rust SDK wasm32 compilation target for web usage.

Added web feature flag, incompatible with non-wasm32 targets.
Replaced unmaintained anymap crate with anymap3.

API and ABI breaking changes

None. Most changes apply only to the wasm32 target, so there are no global breaking changes. The main differences to the native targets are:

DBConnectionBuilder::build is now async on the web.
DbConnection's run_threaded and advance_one_message_blocking unavailable for the wasm32 target.
Added DbConnection::run_background_task as replacement for run_threaded on the web.
Authorization token is sent as a query parameter instead of in a header, due to browser limitation.
Credentials handling:
- File struct unavailable on the web.
- Two browser-friendly options are provided:
  - The re-exported API from gloo_storage for local/session storage.
  - A Cookie builder to manage cookies (except HttpOnly cookies).

Expected complexity level and risk

Estimated at 2:

Most work involves adjusting dependencies and feature flags.
Non-blocking alternatives replace a few native SDK code paths.

Testing

I built 2 demos to exercise the changes:

Bevy https://github.com/thlsrms/tictactoe-stdb-bevy
Leptos https://github.com/thlsrms/stdb-leptos-quickstart

Note: No automated tests have been written yet.

CLAassistant · 2025-05-05T23:28:28Z

All committers have signed the CLA.

bfops · 2025-05-27T17:20:40Z

@thlsrms Thank you for opening this! What's the current status? Are there parts still in progress, or should we be getting a reviewer on this?

thlsrms · 2025-05-27T22:57:04Z

@thlsrms Thank you for opening this! What's the current status? Are there parts still in progress, or should we be getting a reviewer on this?

I've been working on support for the wasm32-unknown-emscripten target on this branch: https://github.com/thlsrms/SpacetimeDB/blob/rust-emscripten-sdk/crates/sdk/src/emscripten.rs, with the intention of including it in this PR. While it's functional on Chromium, Firefox requires further effort.

To keep this PR focused, I'll defer the emscripten support to a separate PR if necessary.

I'll make some minor adjustments and rebase onto master. I'll ping you tomorrow if that's alright.

bfops · 2025-05-27T23:24:01Z

@thlsrms absolutely, thank you!

and no rush. I'm going to be out of office Wed-Fri this week, but either way it might take a little while for us to get around to reviewing, since we have some other things in progress right now.

thlsrms · 2025-05-28T21:29:10Z

@bfops When you're available, feel free to assign a reviewer. 👍

geoffreygarrett · 2025-06-03T09:41:44Z

+1

enaut · 2025-06-21T14:15:44Z

In case it helps someone: I created a proof of concept integration of spacetime into Dioxus - it works™, however it does not feel very native as the interaction with the signals Dioxus uses for its state tracking does not seem very good yet (https://github.com/enaut/kommunikationszentrum/blob/7d04e04c4fede15101f995bec74e1b23adf7d68d/admin/src/main.rs). It might also be that I know neither spacetime nor Dioxus too well, so I might just have not found the clean solution. Nonetheless, I wanted to share that this PR works for Dioxus too. I did not test the updated spacetime generate as I just applied the changes manually.

liamaharon · 2025-09-04T23:22:13Z

Thanks so much @thlsrms for your work here! Your branch got a little stale, I had a go merging master into it, if you are interested in cherry-picking: master...liamaharon:SpacetimeDB:rust-web-sdk-updated

It compiles to wasm and native, but I have not yet tested it thoroughly.

@bfops how are priorities looking on your end? It would be great if this could eventually be merged.

thlsrms · 2025-10-07T10:19:56Z

@liamaharon Thanks, and your merge was on point.
Sorry for the dealy, was AFK this past month.

I had some time this morning to fix the conflicts and rebase.

gefjon · 2025-10-14T20:00:47Z

Why is it necessary for DbConnectionBuilder::build to be async? I find this an undesirable difference from the regular API, and it doesn't seem obviously necessary. Of course, I don't write Rust for the browser target, so I may be missing something obvious.

Why do we need to pass the auth token as a query parameter? If it is necessary, are we obtaining a short--lived token via /v1/identity/websocket-token POST, or are we just putting the user's long-lived token directly into the URL?

thlsrms · 2025-10-16T11:36:48Z

Why is it necessary for DbConnectionBuilder::build to be async? I find this an undesirable difference from the regular API, and it doesn't seem obviously necessary. Of course, I don't write Rust for the browser target, so I may be missing something obvious.

The native version relies on tokio's block_in_place function which blocks the current thread until the connection task is finished, this is unavailable in the browser's single-threaded environment. Making it async also passes the polling responsibility to the application level, which allows the caller to integrate the connection into their asynchronous executor.

Why do we need to pass the auth token as a query parameter? If it is necessary, are we obtaining a short--lived token via /v1/identity/websocket-token POST, or are we just putting the user's long-lived token directly into the URL?

This is a limitation on the browser's websocket API which doesn't allow header manipulation. Yes, before building the connection uri we call fetch_ws_token to get a short-lived one when an auth token is used.

gefjon

I can't say I love making build be async, but I see that it's necessary, so what are you gonna do.

We're discussing internally how to get this tested. Once that's figured out, we should be able to merge this.

crates/codegen/src/rust.rs

sdks/rust/src/db_connection.rs

jdetter · 2025-10-22T18:55:32Z

When/If this merges give me a ping on this so we can move forward this ticket: #3462

kistz

I am no member of clockworklabs just a guy but thought this could be useful info :>

sdks/rust/Cargo.toml

cheekyleek · 2025-10-23T21:22:49Z

Very excited about this

thlsrms · 2025-10-23T22:05:59Z

@gefjon Thanks for taking a look at this, I'll try tackling it over the weekend or at the start of the next week.

gefjon

This is looking great! A few minor things, then if you can get this updated for latest master and passing CI, I think we'll be good to go.

crates/codegen/src/rust.rs

gefjon · 2025-11-19T15:49:31Z

sdks/rust/src/client_cache.rs

    pub fn add_unique_constraint<Col>(&mut self, unique_index_name: &'static str, get_unique_col: fn(&Row) -> &Col)
    where
-        Col: Any + Clone + std::hash::Hash + Eq + Send + Sync + std::fmt::Debug + 'static,
+        Col: std::any::Any + Clone + std::hash::Hash + Eq + Send + Sync + std::fmt::Debug + 'static,


Why did this change?

gefjon · 2025-11-19T15:52:48Z

Cargo.toml

 ahash = { version = "0.8", default-features = false, features = ["std"] }
 anyhow = "1.0.68"
-anymap = "0.12"
+anymap = { package = "anymap3", version = "1.0.1" }


Please update your PR description to document & justify this change.

jazzay · 2025-11-20T16:19:42Z

@thlsrms any chance you could wrap this up in time for the next stdb release?

thlsrms · 2025-11-20T23:16:40Z

@thlsrms any chance you could wrap this up in time for the next stdb release?

Yes! I'll do my best to do it Saturday morning!

- `DbConnectionBuilder::build` becomes async without tokio's block_in_place. Still need to add `web` feature flag.

Renamed the `run_threaded` method on `wasm32` to better reflect its behavior of spawning a background task. The generated `DbConnection` methods `run_threaded`, `run_background`, and `advance_one_message_blocking` now include runtime panics with a clear error feedback when called on unsupported targets.

Trim down repetitive `cfg` clauses by extracting common lock patterns into `get_lock_[sync|async]`.

Moves the creation of DbContextImplInner and DbContextImpl into private helper functions (`build_db_ctx_inner` and `build_db_ctx`) to reduce duplication between the web and non-web implementations of `build_impl`.

gefjon · 2025-11-26T14:26:55Z

Replaced unmaintained anymap crate with anymap3.

If the only reason to replace anymap with anymap3 is that the former is unmaintained, that's not a compelling enough reason to make the change, and certainly not strong enough to make it in an unrelated PR. If anymap was in a good state when it stopped receiving updates, we'd rather continue using it as-is than take the time to evaluate and test a new crate. And more importantly, if we need or want to switch for reasons not directly related to adding Wasm32 support to the Rust client SDK, then the switch should be a separate PR.

What I'm looking for in the PR description is: Why is it a necessity that we switch to anymap3 in this PR, in order to make the Rust client SDK work on the Wasm32 target.

kistz · 2025-12-02T14:46:56Z

@thlsrms do you have any capacity at the moment to adress the feedback? (gentle ping, no rush, hope it is not annoying)

drdozer · 2026-01-16T23:30:08Z

Any progress on this? If you need an extra pair of hands for something, I can help. I would very much like to explore SpacetimeDB+dioxus, and this is a blocking issue for me.

enaut · 2026-01-17T06:25:23Z

@drdozer I already did explore spacetime+dioxus: enaut/dioxus_use_spacetime#1 (AI was used)

There I'm more or less also waiting for wasm support to continue. But it already works with the git dependency on this PR

enaut · 2026-01-17T07:46:08Z

@drdozer sorry the mixup I actually wrote an additional language export which had way better ergonomics than my first try: enaut#2 (branch here: https://github.com/enaut/SpacetimeDB/tree/copilot/explore-dioxus-signals-hooks ) when using... what it basically does is it hooks in the spacetime generate step and generates dioxus native signals so that it easily/natively integrates.

enaut · 2026-01-20T12:20:57Z

@gefjon You can just revert 51b77f0 . the commit does mention a crash - that I did not experience... so I don't know why the dependency was added... but I think that could be handled in a separate PR. That way this PR could be merged and wasm support could land!

drdozer · 2026-02-05T21:31:11Z

@drdozer sorry the mixup I actually wrote an additional language export [...] what it basically does is it hooks in the spacetime generate step and generates dioxus native signals so that it easily/natively integrates.

That looks really nice. Was there a reason you closed that pull request without merging? Sorry, I'm still trying to carve out some time where I can try this stuff out.

enaut · 2026-02-06T07:10:05Z

That looks really nice. Was there a reason you closed that pull request without merging? Sorry, I'm still trying to carve out some time where I can try this stuff out.

@drdozer I'm not yet confident enough it is actually any good... I had the Idea and thought AI might generate something useful - It did do rather well - I think. I haven't had any time to thoroughly test anything, though. And I don't want to just open a PR here and let someone else sift through the AI stuff... the PR was mostly for copilot to have something to work with and was only as merge into my own fork... If you are interested and you don't mind that it is untested AI you are quite welcome to comment on the stuff... I also generated a proof of concept TODOmvc with it... That I only have offline... I could publish that too if you are interested...

shahroz-wilder · 2026-03-02T15:55:11Z

Looking forward for this one 🙌

bfops · 2026-03-18T19:04:21Z

Thank you for opening this! Closing this since #4089 is based on this and updates it for more recent versions of master.

thlsrms force-pushed the rust-web-sdk branch from d2011c8 to e781955 Compare May 12, 2025 10:48

akaia-shadowfox mentioned this pull request May 14, 2025

Spacetimedb in browser #2699

Open

thlsrms force-pushed the rust-web-sdk branch from b56b76c to 89b9d9d Compare May 28, 2025 21:13

thlsrms marked this pull request as ready for review May 28, 2025 21:29

thlsrms force-pushed the rust-web-sdk branch from 89b9d9d to 256077c Compare October 7, 2025 10:16

bfops mentioned this pull request Oct 14, 2025

The module binding code compile to wasm failed. #2602

Open

gefjon reviewed Oct 22, 2025

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crates/codegen/src/rust.rs Outdated Show resolved Hide resolved

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gefjon mentioned this pull request Oct 22, 2025

Test Rust client SDK WASM target in CI #3462

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kistz reviewed Oct 23, 2025

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thlsrms force-pushed the rust-web-sdk branch from aa707d5 to 9e5dda7 Compare October 28, 2025 16:12

gefjon reviewed Nov 19, 2025

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thlsrms added 3 commits November 22, 2025 18:20

Replace SDK File struct with StorageEntry for web

ad530a6

Enable web build for the SDK crate

60edc8b

- `DbConnectionBuilder::build` becomes async without tokio's block_in_place. Still need to add `web` feature flag.

Enable run_threaded on the web with spawn_local

942751c

thlsrms added 16 commits November 22, 2025 18:22

Improve Rust SDK websocket message handling on wasm32

22dc7cd

Add cookie API and re-export gloo storage wrappers for the web SDK

27824b3

Remove some redundancies from wasm32 rust sdk

1fd105c

Add web feature flag to the rust sdk

33668b0

Add token verification for the wasm sdk websocket connection

46d94b4

Reduce cfg noise by simplifying mutex handling in the sdk crate

f578761

Trim down repetitive `cfg` clauses by extracting common lock patterns into `get_lock_[sync|async]`.

Remove tokio dependency from the rust web sdk

a87b1e0

Improve error handling for the wasm sdk's Cookie builder

ec6cdec

Use conditional type aliases to reduce cfg noise on structs

d2c2548

Consolidate web/non-web build_impl functions

7574854

Moves the creation of DbContextImplInner and DbContextImpl into private helper functions (`build_db_ctx_inner` and `build_db_ctx`) to reduce duplication between the web and non-web implementations of `build_impl`.

Enforce compile error on non-portable DbConnection methods

5801280

Bump getrandom to 0.3.4, remove legacy RUSTFLAGS requirement

4b96c72

Minor formatting and code simplification for clippy

ec43e45

Rename run_background to run_background_task for clarity

d10a591

Hide wasm-only DbConnection methods in native docs

bba3378

thlsrms force-pushed the rust-web-sdk branch from 9e5dda7 to bba3378 Compare November 23, 2025 15:18

kistz mentioned this pull request Jan 21, 2026

Add wasm32 support to the rust sdk (updated) #4089

Closed

1 task

drdozer mentioned this pull request Feb 17, 2026

Add wasm32/web browser support to the Rust SDK #4319

Closed

bfops closed this Mar 18, 2026

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Description of Changes

API and ABI breaking changes

Expected complexity level and risk

Testing

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