feat(lsp): improve logging (#15636)

* Simplify rpc encode/decode messages to rpc.send/rcp.receive
* Make missing handlers message throw a warning
* Clean up formatting style in log
* Move all non-RPC loop messages to trace instead of debug
* Add format func option to log to allow newlines in per log entry

1 files changed, 13 insertions, 5 deletions

diff --git a/runtime/lua/vim/lsp/log.lua b/runtime/lua/vim/lsp/log.lua
index 5d2e396cc5..4597f1919a 100644
--- a/runtime/lua/vim/lsp/log.lua
+++ b/runtime/lua/vim/lsp/log.lua
@@ -14,7 +14,8 @@ log.levels = vim.deepcopy(vim.log.levels)
 
 -- Default log level is warn.
 local current_log_level = log.levels.WARN
-local log_date_format = "%FT%H:%M:%S%z"
+local log_date_format = "%F %H:%M:%S"
+local format_func = function(arg) return vim.inspect(arg, {newline=''}) end
 
 do
   local path_sep = vim.loop.os_uname().version:match("Windows") and "\\" or "/"
@@ -44,7 +45,7 @@ do
   end
 
   -- Start message for logging
-  logfile:write(string.format("[ START ] %s ] LSP logging initiated\n", os.date(log_date_format)))
+  logfile:write(string.format("[START][%s] LSP logging initiated\n", os.date(log_date_format)))
   for level, levelnr in pairs(log.levels) do
     -- Also export the log level on the root object.
     log[level] = levelnr
@@ -67,14 +68,14 @@ do
       if levelnr < current_log_level then return false end
       if argc == 0 then return true end
       local info = debug.getinfo(2, "Sl")
-      local fileinfo = string.format("%s:%s", info.short_src, info.currentline)
-      local parts = { table.concat({"[", level, "]", os.date(log_date_format), "]", fileinfo, "]"}, " ") }
+      local header = string.format("[%s][%s] ...%s:%s", level, os.date(log_date_format), string.sub(info.short_src, #info.short_src - 15), info.currentline)
+      local parts = { header }
       for i = 1, argc do
         local arg = select(i, ...)
         if arg == nil then
           table.insert(parts, "nil")
         else
-          table.insert(parts, vim.inspect(arg, {newline=''}))
+          table.insert(parts, format_func(arg))
         end
       end
       logfile:write(table.concat(parts, '\t'), "\n")
@@ -104,6 +105,13 @@ function log.get_level()
   return current_log_level
 end
 
+--- Sets formatting function used to format logs
+---@param handle function function to apply to logging arguments, pass vim.inspect for multi-line formatting
+function log.set_format_func(handle)
+  assert(handle == vim.inspect or type(handle) == 'function', "handle must be a function")
+  format_func = handle
+end
+
 --- Checks whether the level is sufficient for logging.
 ---@param level number log level
 ---@returns (bool) true if would log, false if not