fix supporting unicode in signature

Author: sumneko

script/proto/converter.lua

@@ -207,6 +207,14 @@ function m.setOffsetEncoding(encoding)
     offsetEncoding = encoding:lower():gsub('%-', '')
 end
 
+---@param s        string
+---@param i?       integer
+---@param j?       integer
+---@return integer
+function m.len(s, i, j)
+    return encoder.len(offsetEncoding, s, i, j)
+end
+
 ---@class proto.command
 ---@field title string
 ---@field command string

script/provider/provider.lua

@@ -772,8 +772,8 @@ m.register 'textDocument/signatureHelp' {
             for j, param in ipairs(result.params) do
                 parameters[j] = {
                     label = {
-                        param.label[1],
-                        param.label[2],
+                        converter.len(result.label, 1, param.label[1]),
+                        converter.len(result.label, 1, param.label[2]),
                     }
                 }
             end

test/signature/init.lua

@@ -330,3 +330,17 @@ t(<??>)
 {
 'function (<!x: number!>)',
 }
+
+TEST [[
+---@class 😅
+
+---@param a 😅
+---@param b integer
+local function f(a, b)
+end
+
+f(1, 2<??>)
+]]
+{
+'function f(a: 😅, <!b: integer!>)',
+}