the `wasm32-wasi` target may not be installed while it is installed

Question

why cargo build --target wasm32-wasi throws and error about not having wasm32-wasi while it is installed. steps to reproduce

1. cargo new train
2. rustup target add wasm32-wasi
3. cargo build --target wasm32-wasi

the output to the console is next

➜  train git:(master) ✗ cargo build --target wasm32-wasi
   Compiling train v0.1.0 (/user/playground/rustLang/train)
error[E0463]: can't find crate for `std`
  |
  = note: the `wasm32-wasi` target may not be installed
  = help: consider downloading the target with `rustup target add wasm32-wasi`

error: cannot find macro `println` in this scope
 --> src/main.rs:2:5
  |
2 |     println!("hello");
  |     ^^^^^^^

error: requires `sized` lang_item

For more information about this error, try `rustc --explain E0463`.
error: could not compile `train` due to 3 previous errors
➜  train git:(master) ✗ rustup target add wasm32-wasi
info: component 'rust-std' for target 'wasm32-wasi' is up to date
➜  train git:(master) ✗ 

Answer 1

You already had the answer in the line:

help: consider downloading the target with rustup target add wasm32-wasi

in the command prompt just type: > rustup target install wasm32-wasi

Answer 2

So, it seems that you didn't register the terminal before run the command: Please confirm that you have installed emsdk from: emscripten

After downloaded open the powershell terminal and go to emsdk folder and execute the following commands:

./emsdk install latest

./emsdk activate latest

In the emsdk and wat2wasm documentation it is necessary to register the terminal and load the emsdk references before executing any other command. In the documentation, you are instructed to do this procedure every time for each new instance or new terminal window opened.

Reinstall rust from: rust

check if environment variables are ok and try again

Answer 3

I had the same problem. I'm on MacOS:

❮ cargo wasi build --release                                                                                                         
error: failed to find the `wasm32-wasi` target installed, and rustup is also not detected, you'll need to be sure to install the `wasm32-wasi` target before using this command

It turns out that I was using a homebrew installation of rust:

❯ which cargo                                                                                                                          
/opt/homebrew/bin/cargo

The solution was to uninstall the homebrew version of rust and then install the version from the instructions on rust-lang.org (actual code may vary. Just got to https://www.rust-lang.org/tools/install and follow the instructions)

❯ brew uninstall rust                                                                                                                  
Uninstalling /opt/homebrew/Cellar/rust/1.67.1... (36,648 files, 891.6MB)

❯ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh