Unused local variable ignore pattern

[smackesey]

This is a feature request. Whenever one writes functions against implementing some interface (e.g. that will be called by external code), it's common to have parameters that may not be used:

local myFunction(arg1, arg2)
  print('This function doesn't actually use the args passed to it.)
end

A lot of the time it's useful to keep these args listed for documentation/standardization purposes. A common cross-language convention is to prefix known unused variables with a leading underscore:

local myFunction(_arg1, _arg2)
  print("This function doesn't actually use the args passed to it.")
end

Right now (so far as I can tell), there is no way to turn off the unused variable warnings for just variables with a leading underscore-- you either turn off all unused variable warnings, or none. I think it would be good to provide a "Lua.diagnostics.unusedVariableIgnorePattern" or similar.

[sumneko]

Currently I support the use of _ to represent a dummy name, which will be ruled out by almost all diagnostics.

In addition, in VSCode, the diagnosis will only darken the color of the variable and will not cause additional interference. I think it is acceptable.
If you are using another client and made this request because of interference from this diagnosis, then I suggest requesting that the client you are using supports this feature: https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#diagnosticTag

[idbrii]

This feature would also be helpful for writing tests in lua-testy where you write local functions prefixed with test_.