Write a library to interface between Lua, and wasm, for enabling communication between plugins and the Neovim apis. The library language is Rust, as it is to be dynamically loaded via lua, using the neovim api, instead of going via the rpc route which creates a networking bottleneck between two or more different process, this route allows for a single process (NEOVIM) , while also a plugin ecosystem that allows any programming language that can compile to wasm.

• The first test is a poor mans performance test implementation, that imitates Bram's implementation of just summing a number inside a for loop, wasm is faster by 99%, due to compiler optimizations of the language om this case it is zig, this mostly shows the compilation optmization benefits that compiling to wasm could bring to the table vs JIT with LuaJIT.

• The second one is a test where we try get the prime numbers between 0-10000, and count the number of times it could be achieved within 5 seconds, there is no constants, so even the wasm compiled shouldn't optimize the away almost all the operations like it did in the first test. Here wasm was 99% faster than Luajit. I didn't want to optmize the algorithm for each specific language, instead used basic structures, and avoid bitwise manipulation or stack pre allocation even on the zig/wasm side.

• This image shows the tests:

• To run this test simply run the bellow:

  cargo make perf

  Requires:

  • cargo-make which can be installed by cargo install cargo-make .
  • zig to be in system path, can be installed from Download ⚡ Zig Programming Language (ziglang.org)

• Overall Wasm should be faster than luajit on average, without trying any fancy optimization techniques, for a wider range of luajit vs wasm comparisons one can check here

NOTE: Current perf test results shown are from a Windows 10 PC. That's the machine I have.

• Wasm memory allocation and dealocation

We would need an allocation and deallocation function implementation on every wasm module, that the developers of it would need to create for themselves as data between the host (this rust library) and the wasm plugin can only currently be shared using i32 or f32, directly, but other objects like buffers, structs, etc, need more than just 32bits therefore we communicate using pointers to memory to the module to access and manipulate the data from the host side, where applicable, and normally this involves json.

-- for downloading shared librar from releases do this
-- if you don't want to build from source and just get
-- going. Warning, only supports, windows, linux, and macos
require("wasm_nvim_dl").download("windows")
-- Replace "windows" with either "linux", or "macos" for respective OS.

-- load wasm_nvim
local wasm = require("wasm_nvim")

-- this next line scan and load .wasm files into space
-- should be called only once, preferebly on your init.lua
wasm.setup {
  --debug = true -- uncomment to see debug info printed out, good for debugging issues.
}

-- Here tests is a wasm file, test.wasm inside a ./wasm folder
-- located in neovim runtimepath.
-- The luaExecExample is an example of a function exposed by the test.wasm module.
wasm.tests.luaExecExample();

cargo make build

Then move the shared library from /target/release/*.so or *.dll to a ./lua folder on the neovim runtime path so as to use it.

• Cargo Make cargo install cargo-make

• a function called functionality that is exposed/exported so that it can be called from wasm_nvim library. The function returns a json defining what functions are exported, and what they take as parameters, also what they return.

  An example:

  export fn functionality() u32 {
      var functions = ArrayList(Functionality).init(aloc);
      _ = functions.append(CreateFunctionality("hi", "void", "void")) catch undefined;
      var stringified = ArrayList(u8).init(aloc);
      json.stringify(functions.items, .{}, stringified.writer()) catch undefined;
      var unmanaged = stringified.moveToUnmanaged();
      // get id for setting a value
      const id = get_id();
      const addr = get_addr(&unmanaged.items[0]);
      //set the value to be consumed as a return type of this function
      set_value(id, addr, unmanaged.items.len);
      return id;
  }
  

  it returns an id, that maps to a json which was created by the set_value() function, which points to a json string that defines the functions and parameters exported by the module to be consumed. In this case the json would like like bellow:

  [{"name":"hi", "params": "void", "returns": "void"}]

  • Params field: Can be "void" or anything else, doesn't really matter. When "void" means the function tagged by "name" consumes/accepts nothing.

  • Returns field: Same situation as Params field above, anything but void means the function returns something, else returns void.

    These fields are necessary when functions are being exported by wasm module, so that lua end that might call them has ability to get values if they are returned, or pass value to the function if it is expecting some.

This section exists, because we currently can't directly interact with Neovim API's that require lua function as references or callbacks in parameters, so users might need to wrap their wasm callbacks into a lua function, and make the neovim api from that side as a solution for the time being. NOTE: If you come across a neovim api that requires a lua function or callback in params, then make a PR to the ./API.MD file adding it to the list, or you can also create an issue.

• extern "host" get_id() u32;

  Get a unique id to be used for sharing data between wasm module and outside world.

• extern "host" get_addr(*u8) u32;

  Get the address from the host in terms of the memory of the module

• extern "host" get_value_addr(id: u32) [*]u8;

  Usable for getting location of value that was created from outside world of module. The value pointed here is to be managed by the module, and deallocated. NOTE: value is cleared from memory of outside world once called, make sure to call before get_value_size, so as to know the length before calling this function

• extern "host" get_value_size(id: u32) u32;

  Given an id to a value, it returns the size of the value located at given id. This should be called before get_value_addr as that would clear the id from memory.

  s

• extern "host" set_value(id: u32, loc: u32, size: u32) void;

  Used for returning/setting a value to the wasm_nvim library or to the outside world from the wasm module using it. Users of this method should make sure the relinquish memory control of any thing the pointer is pointing to.

• extern "host" lua_exec(id: u32) void;

  Executes lua script which is string, created, and passed to host via get_id andset_value combination, the id of the string is then passed to this function which it will then be executed.

  NOTE: This prints out the loaded string to output on some neovim versions, eg: 0.9.1 on windows.

• extern "host"lua_eval(id: u32) u32;

  Similar to lua_exec except that this one evaluates expressions and will return a value that is mapped to the id. The value returned will say "null", if the expression evaluated returned nothing, otherwise the value would contain the contents of the results

  NOTE: This is for expressions, anything else passed to this function can result to undefined behavior