How To Access the Server Instance

Using language server methods inside registered features and commands are quite common. We recommend adding language server as a first parameter of a registered function.

Why not use server inside the function?

Using the outer server instance inside registered function will make writing unit tests more difficult as you can no longer simulate different scenarios by modifying the server instance you pass to the handler function.

There are two ways of doing this:

• Add a type annotation to first parameter (recommended)

  Add the LanguageServer class (or any class derived from it) as the type annotation to first parameter of a function, pygls will detect this and automatically pass the language server instance.

  @server.command('countdown.blocking')
  def count_down_10_seconds_blocking(ser: JsonLanguageServer, *args):
      # Omitted
  

• ls (language server) naming convention (preserved for backwards compatibility)

  Name the first parameter ls, pygls will automatically pass the language server instance.

  @server.command('countdown.blocking')
  def count_down_10_seconds_blocking(ls, *args):
      # Omitted