Ari Seyhun (Nov 23 2023 at 05:54): Ari Seyhun (Nov 23 2023 at 05:54):When building my component with wasm-tools component new, I get an error:
module requires an import interface named `__wbindgen_placeholder__`
This only occurs when I include a local crate as a dependency (and use it).
I'm not sure what part of this dependency is causing this issue, but the dependency itself has nothing to do with wasm, and is just a regular rust crate.
From digging into the code of wasm bindgen, it seems like __wbindgen_placeholder__ is supposed to get replaced with something, however in my case it isn't?
Ari Seyhun (Nov 23 2023 at 06:04):Sorry it doesn't work, here's the current output:
❯ wasm-tools component new ./target/wasm32-wasi/release/game.wasm -o ./modules/game.wasm --adapt ./../../../thalo-rs/thalo/crates/thalo_cli/wasi_snapshot_preview1.wasm
error: failed to encode a component from module
Caused by:
0: module requires an import interface named `__wbindgen_placeholder__`
This indicates that wasm bindgen is being used but that's not compatible with components so the only fix will be to figure out what's depending on wasm bindgen and to either update or remove that dependency
Ari Seyhun (Nov 23 2023 at 06:28):That's strange, it would make sense however when I do cargo tree -p game or cargo tree -i wasm-bindgen, it's not a dependency of the game wasm component being generated.
It is a dependency used within the cargo workspace I'm in, but I don't think that should import wasm bindgen
Ari Seyhun (Nov 23 2023 at 06:32): Ari Seyhun (Nov 23 2023 at 06:32):I've just posted the output of running cargo tree -p game
Ari Seyhun (Nov 23 2023 at 07:40):Ah I forgot to do --target wasm32-wasi when creating the tree! Looks like the bson crate was the issue, using wasm-bindgen.
Notification Bot (Nov 23 2023 at 07:40):Ari Seyhun has marked this topic as resolved.
Ari Seyhun (Nov 23 2023 at 07:53):https://github.com/mongodb/bson-rust/issues/441
Last updated: Dec 06 2025 at 06:05 UTC