feat(yamlls): force documentFormattingProvider=true #4016

Problem:
The current version of the config will let you do formatting manually
`:lua vim.lsp.buf.format()` but the lsp doesn't have capabilities
registered correctly so if you use auto formatting like outlined in
[help pages](https://neovim.io/doc/user/lsp.html#lsp-attach)

    if not client:supports_method('textDocument/willSaveWaitUntil')
        and client:supports_method('textDocument/formatting') then
      vim.api.nvim_create_autocmd('BufWritePre', {
        group = vim.api.nvim_create_augroup('my.lsp', {clear=false}),
        buffer = args.buf,
        callback = function()
          vim.lsp.buf.format({ bufnr = args.buf, id = client.id, timeout_ms = 1000 })
        end,
      })
    end

, it won't enable for the yaml lsp because
`client:supports_method('textDocument/formatting')` returns false.

Solution:
The `on_init` hook, while hacky, will mark the capability as true.

1 files changed, 7 insertions, 0 deletions

diff --git a/lsp/yamlls.lua b/lsp/yamlls.lua
index 586745a7..04e837e1 100644
--- a/lsp/yamlls.lua
+++ b/lsp/yamlls.lua
@@ -70,4 +70,11 @@ return {
     -- formatting disabled by default in yaml-language-server; enable it
     yaml = { format = { enable = true } },
   },
+  on_init = function(client)
+    --- https://github.com/neovim/nvim-lspconfig/pull/4016
+    --- Since formatting is disabled by default if you check `client:supports_method('textDocument/formatting')`
+    --- during `LspAttach` it will return `false`. This hack sets the capability to `true` to facilitate
+    --- autocmd's which check this capability
+    client.server_capabilities.documentFormattingProvider = true
+  end,
 }