async.nvim

Small async library for Neovim plugins

Example

Take the current function that uses a callback style function to run a system process.

local function run_job(cmd, args, callback)
  local handle
  handle = vim.uv.spawn(cmd, { args  = args, },
    function(code)
      s.handle:close()
      callback(code)
    end
  )
end

If we want to emulate something like:

echo foo && echo bar && echo baz

Would need to be implemented as:

run_job('echo', {'foo'},
  function(code1)
    if code1 ~= 0 then
      return
    end
    run_job('echo', {'bar'},
      function(code2)
        if code2 ~= 0 then
          return
        end
        run_job('echo', {'baz'})
      end
    )
  end
)

As you can see, this quickly gets unwieldy the more jobs we want to run.

async.nvim simplifies this significantly.

First we turn this into an async function using wrap:

local a = require('async')

local run_job_a = a.wrap(3, run_job)

Now we need to create a top level function to initialize the async context. To do this we can use void or sync.

Note: the main difference between void and sync is that sync functions can be called with a callback (like the run_job in a non-async context, however the user must provide the number of agurments.

For this example we will use void:

local main = a.sync(0, function()
  local code1 = run_job_a('echo', {'foo'})
  if code1 ~= 0 then
    return
  end

  local code2 = run_job_a('echo', {'bar'})
  if code2 ~= 0 then
    return
  end

  run_job_a('echo', {'baz'})
end)

main()

We can now call run_job_a in linear imperative fashion without needing to define callbacks. The arguments provided to the callback in the original function are simply returned by the async version.