Add workspace/configuration handler that recognizes insertSpaces/tabSize

If using a eclipse.jdt.ls version that includes
eclipse-jdtls/eclipse.jdt.ls#1657 this will finally
make code-actions respect the clients shiftwidth/expandtab options and
no longer include tabs when the user uses spaces.

The alternative to overriding the handler would have been to document
that users should include these options in their `config.settings`, but
given that there is no good reason that I can think of where you don't
want to respond with your local editor settings it seems justified to
include this out of the box instead of requiring every user to add this.

lua/jdtls/setup.lua

@@ -53,6 +53,34 @@ local extendedClientCapabilities = {
 };
 
 
+local function configuration_handler(err, _, params, client_id, bufnr, config)
+ assert(not err, vim.inspect(err))
+ local client = vim.lsp.get_client_by_id(client_id)
+ if not client then
+ vim.notify('LSP[id=' .. client_id .. '] client has shut down after sending the message', vim.log.levels.ERROR)
+ return
+ end
+
+ local result = {}
+ for _, item in ipairs(params.items or {}) do
+ if item.section == 'java.format.insertSpaces' then
+ table.insert(result, vim.bo.expandtab)
+ elseif item.section == 'java.format.tabSize' then
+ local sts = vim.bo.softtabstop
+ local tab_size = (sts > 0 and sts) or (sts < 0 and vim.bo.shiftwidth) or vim.bo.tabstop
+ table.insert(result, tab_size)
+ else
+ local value = vim.lsp.util.lookup_section(client.config.settings, item.section) or vim.NIL
+ if value == vim.NIL and item.section == '' then
+ value = client.config.settings or vim.NIL
+ end
+ table.insert(result, value)
+ end
+ end
+ return result
+end
+
+
 local function start_or_attach(config)
  assert(config, 'config is required')
  assert(
@@ -82,6 +110,7 @@ local function start_or_attach(config)
  )
  config.handlers = config.handlers or {}
  config.handlers['language/status'] = config.handlers['language/status'] or status_callback
+ config.handlers['workspace/configuration'] = config.handlers['workspace/configuration'] or configuration_handler
  config.capabilities = config.capabilities or lsp.protocol.make_client_capabilities()
  config.capabilities.textDocument.codeAction = {
  dynamicRegistration = false;