fix: generic linter

[xiaoshihou514]

closes #132

[UnderCooled]

This fix miss these conditions:

-- you need to check ft_handler(...).linter
ft('foo'):fmt(...)
ft('*'):lint(...)

-- merge two linter list
ft('foo'):lint(...)
ft('*'):lint(...)

[UnderCooled]

I'm not really sure whether this fix is elegant.

  local buf_config = ft_handler[vim.bo[buf].filetype]
  local generic_config = ft_handler['*']
  if not (buf_config or generic_config) then
    return
  end
  local linters = buf_config.linter or {}
  if generic_config.linter then
    vim.list_extend(linters, generic_config.linter)
  end

[xiaoshihou514]

I'm not really sure whether this fix is elegant.

  local buf_config = ft_handler[vim.bo[buf].filetype]
  local generic_config = ft_handler['*']
  if not (buf_config or generic_config) then
    return
  end
  local linters = buf_config.linter or {}
  if generic_config.linter then
    vim.list_extend(linters, generic_config.linter)
  end

If it doesn't modify the original table then it seems fine.

[UnderCooled]

if not (buf_config or generic_config) is wrong, may cause buf_config.linter index on nil.

This is an uglier solution 🤣

  local buf_config = ft_handler[vim.bo[buf].filetype]
  local generic_config = ft_handler['*']
  local linters = {}
  if buf_config and buf_config.linter then
    vim.list_extend(linters, buf_config.linter)
  end
  if generic_config and generic_config.linter then
    vim.list_extend(linters, generic_config.linter)
  end
  if #linters == 0 then
    return
  end

[xiaoshihou514]

Hmm, actually we should have a pre-condition that buf_config.linter is not nil or this autocmd wouldn't have been registered in the first place. But it is possible the configuration tables are modified during runtime, anyway, this deserves a refactor.