fix(lsp.buf): use correct offset_encoding for all requests

Problem:

`lsp.buf_request` send the same params to all servers and many
calls to this pass PositionalParams which depends on the clients
offset_encoding. This can result with incorrect params being sent
to a server.

Solution:

`lsp.buf_request` `params` argument can now be passed as a function
which takes the client as the first argument. This is used in
lsp/buf.lua to construct correct params for each client request.

1 files changed, 3 insertions, 2 deletions

diff --git a/runtime/lua/vim/lsp.lua b/runtime/lua/vim/lsp.lua
index 76658b7012..4f13ad5721 100644
--- a/runtime/lua/vim/lsp.lua
+++ b/runtime/lua/vim/lsp.lua
@@ -854,7 +854,7 @@ api.nvim_create_autocmd('VimLeavePre', {
 ---
 ---@param bufnr (integer) Buffer handle, or 0 for current.
 ---@param method (string) LSP method name
----@param params table|nil Parameters to send to the server
+---@param params? table|(fun(client: vim.lsp.Client, bufnr: integer): table?) Parameters to send to the server
 ---@param handler? lsp.Handler See |lsp-handler|
 ---       If nil, follows resolution strategy defined in |lsp-handler-configuration|
 ---@param on_unsupported? fun()
@@ -879,7 +879,8 @@ function lsp.buf_request(bufnr, method, params, handler, on_unsupported)
     if client.supports_method(method, { bufnr = bufnr }) then
       method_supported = true
 
-      local request_success, request_id = client.request(method, params, handler, bufnr)
+      local cparams = type(params) == 'function' and params(client, bufnr) or params --[[@as table?]]
+      local request_success, request_id = client.request(method, cparams, handler, bufnr)
       -- This could only fail if the client shut down in the time since we looked
       -- it up and we did the request, which should be rare.
       if request_success then