Merge WASM Files

[al3xfischer]

Summary

Is there any API to add a function from an other module?

Additional Details

I'm trying to merge two WASM files.
In the first step, I want to merge the functions, but I'm not able to add the function from the module_b to the module_a.
As use can see below, I'm using module.funcs.add_local but the method is expecting a LocalFunction but I didn't find a way to extract the function as a LocalFunction nor did I figure out a way to create it from the Function.
I'm using add_local because I didn't find any other method that allowed me to add a new function to a module.

Is there an API for my use case, or is this currently not supported? (Or am I missing something?.. )

Thanks in advance

use anyhow::Error;
use walrus::*;

fn main() -> Result<(), Error> {
    let module_a = Module::from_file("fancy.wasm")?;

    let module_b = Module::from_file("add.wasm")?;
    //  module_b constians only one func
    let my_fancy_func = module_b.funcs.iter().next().unwrap();

    // let module_a.funcs.add(my_fancy_func)
    // mismachted types exepected struct 'LocalFunction', found 'walrus::Function'
    module_a.funcs.add_local(*my_fancy_func);
    
    Ok(())
}

[deltanedas]

i know this is year late but you can match on function.kind and you get FunctionKind::Local(LocalFunction)

the hard part is making sure all the local and what not play nice in the combined wasm which i have not yet managed

[Germ210]

Perhaps you should try using the program "wasm-merge". It's from binaryen, and I think it's what you are looking for. Essentially it will hook up wasm modules to each other. Their example is this

;; a.wasm
(module
  (import "second" "bar" (func $second.bar))

  (export "main" (func $func))

  (func $func
    (call $second.bar)
  )
)

This module is expecting a bar function from the second module. Now, let's define the second module.

;; b.wasm
(module
  (import "outside" "log" (func $log (param i32)))

  (export "bar" (func $func))

  (func $func
    (call $log
      (i32.const 42)
    )
  )
)

Then we call the command, where we "map" each wasm file with a module name, such as:
wasm-merge a.wasm first b.wasm second -o output.wasm

Which outputs:

(module
  (import "outside" "log" (func $log (param i32)))

  (export "main" (func $func))
  (export "bar" (func $func_2))

  (func $func
    (call $func_2)
  )

  (func $func_2
    (call $log
      (i32.const 42)
    )
  )
)