Build Docker image

[PepaRokos]

I'm trying to build Docker image of my application using Debian Dockerfile from documentation and it fails with:

Building project: rezervator, /app
37.99           FS create_dir_all "target/site/pkg"
37.99      Running cargo build --package=rezervator --lib --target-dir=/app/target/front --target=wasm32-unknown-unknown --no-default-features --features=hydrate --profile=wasm-release
38.14    Compiling proc-macro2 v1.0.93
38.14    Compiling unicode-ident v1.0.16
38.14    Compiling version_check v0.9.5
38.14    Compiling cfg-if v1.0.0
38.14    Compiling serde v1.0.217
38.14    Compiling wasm-bindgen-shared v0.2.100
38.14    Compiling autocfg v1.4.0
38.14    Compiling rustversion v1.0.19
38.16 error[E0463]: can't find crate for `core`
38.16   |
38.16   = note: the `wasm32-unknown-unknown` target may not be installed
38.16   = help: consider downloading the target with `rustup target add wasm32-unknown-unknown`

What's wrong?

[gbj]

As far as the build process, its telling you what's wrong:

38.16   = note: the `wasm32-unknown-unknown` target may not be installed
38.16   = help: consider downloading the target with `rustup target add wasm32-unknown-unknown`

As far as why that's the case: the Dockerfile already adds this target

RUN rustup target add wasm32-unknown-unknown

But it looks like for some reason cargo build isn't finding it.

I can think of two possible explanations:

1. If you've made other changes to the Dockerfile that caused your setup to be different, or
2. If you're using a different toolchain (particularly nightly vs stable). For example, if you used stable but used the nightly builder instead of the stable one that's commented out here

# Get started with a build env with Rust nightly
FROM rustlang/rust:nightly-bullseye as builder

# If you’re using stable, use this instead
# FROM rust:1.86-bullseye as builder

[PepaRokos]

I added RUN rustup default stable before RUN rustup target add wasm32-unknown-unknown to my Dockerfile and it fixed my issue. Build now works. Thank you.