lsp: Add sync variant of LSP formatting

Also, factor out a `vim.lsp.util.get_effective_tabstop()` helper and add
tests for it.

1 files changed, 24 insertions, 0 deletions

diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index 71ca1048e1..2b9b4d8c7e 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -1259,6 +1259,30 @@ function M.make_text_document_params()
   return { uri = vim.uri_from_bufnr(0) }
 end
 
+--- Get visual width of tabstop.
+---
+--@see |softtabstop|
+--@param bufnr (optional, number): Buffer handle, defaults to current
+--@returns (number) tabstop visual width
+function M.get_effective_tabstop(bufnr)
+  validate { bufnr = {bufnr, 'n', true} }
+  local bo = bufnr and vim.bo[bufnr] or vim.bo
+  local sts = bo.softtabstop
+  return (sts > 0 and sts) or (sts < 0 and bo.shiftwidth) or bo.tabstop
+end
+
+function M.make_formatting_params(options)
+  validate { options = {options, 't', true} }
+  options = vim.tbl_extend('keep', options or {}, {
+    tabSize = M.get_effective_tabstop();
+    insertSpaces = vim.bo.expandtab;
+  })
+  return {
+    textDocument = { uri = vim.uri_from_bufnr(0) };
+    options = options;
+  }
+end
+
 -- @param buf buffer handle or 0 for current.
 -- @param row 0-indexed line
 -- @param col 0-indexed byte offset in line