feat(lsp): add logging level "OFF" (#18379)

runtime/doc/lsp.txt

@@ -750,7 +750,9 @@ omnifunc({findstart}, {base})                             *vim.lsp.omnifunc()*
 set_log_level({level})                               *vim.lsp.set_log_level()*
                 Sets the global log level for LSP logging.
 
-                Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR"
+                Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR",
+                "OFF"
+
                 Level numbers begin with "TRACE" at 0
 
                 Use `lsp.log_levels` for reverse lookup.

runtime/doc/lua.txt

@@ -1012,6 +1012,7 @@ Log levels are one of the values defined in `vim.log.levels`:
         vim.log.levels.INFO
         vim.log.levels.TRACE
         vim.log.levels.WARN
+        vim.log.levels.OFF
 
 ------------------------------------------------------------------------------
 LUA-VIMSCRIPT BRIDGE                                    *lua-vimscript*

runtime/lua/vim/_editor.lua

@@ -58,6 +58,7 @@ vim.log = {
     INFO  = 2;
     WARN  = 3;
     ERROR = 4;
+    OFF   = 5;
   }
 }
 

runtime/lua/vim/lsp.lua

@@ -1790,13 +1790,14 @@ end
 --
 -- Can be used to lookup the number from the name or the
 -- name from the number.
--- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR"
+-- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "OFF"
 -- Level numbers begin with "TRACE" at 0
 lsp.log_levels = log.levels
 
 --- Sets the global log level for LSP logging.
 ---
---- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR"
+--- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "OFF"
+---
 --- Level numbers begin with "TRACE" at 0
 ---
 --- Use `lsp.log_levels` for reverse lookup.

runtime/lua/vim/lsp/log.lua

@@ -8,7 +8,7 @@ local log = {}
 -- Log level dictionary with reverse lookup as well.
 --
 -- Can be used to lookup the number from the name or the name from the number.
--- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR"
+-- Levels by name: "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "OFF"
 -- Level numbers begin with "TRACE" at 0
 log.levels = vim.deepcopy(vim.log.levels)
 
@@ -25,27 +25,47 @@ do
   end
   local logfilename = path_join(vim.fn.stdpath('cache'), 'lsp.log')
 
+  -- TODO: Ideally the directory should be created in open_logfile(), right
+  -- before opening the log file, but open_logfile() can be called from libuv
+  -- callbacks, where using fn.mkdir() is not allowed.
+  vim.fn.mkdir(vim.fn.stdpath('cache'), "p")
+
   --- Returns the log filename.
   ---@returns (string) log filename
   function log.get_filename()
     return logfilename
   end
 
-  vim.fn.mkdir(vim.fn.stdpath('cache'), "p")
-  local logfile = assert(io.open(logfilename, "a+"))
+  local logfile, openerr
+  ---@private
+  --- Opens log file. Returns true if file is open, false on error
+  local function open_logfile()
+    -- Try to open file only once
+    if logfile then return true end
+    if openerr then return false end
 
-  local log_info = vim.loop.fs_stat(logfilename)
-  if log_info and log_info.size > 1e9 then
-    local warn_msg = string.format(
-      "LSP client log is large (%d MB): %s",
-      log_info.size / (1000 * 1000),
-      logfilename
-    )
-    vim.notify(warn_msg)
+    logfile, openerr = io.open(logfilename, "a+")
+    if not logfile then
+      local err_msg = string.format("Failed to open LSP client log file: %s", openerr)
+      vim.notify(err_msg, vim.log.levels.ERROR)
+      return false
+    end
+
+    local log_info = vim.loop.fs_stat(logfilename)
+    if log_info and log_info.size > 1e9 then
+      local warn_msg = string.format(
+        "LSP client log is large (%d MB): %s",
+        log_info.size / (1000 * 1000),
+        logfilename
+      )
+      vim.notify(warn_msg)
+    end
+
+    -- Start message for logging
+    logfile:write(string.format("[START][%s] LSP logging initiated\n", os.date(log_date_format)))
+    return true
   end
 
-  -- Start message for logging
-  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
@@ -63,23 +83,26 @@ do
     -- ```
     --
     -- This way you can avoid string allocations if the log level isn't high enough.
-    log[level:lower()] = function(...)
-      local argc = select("#", ...)
-      if levelnr < current_log_level then return false end
-      if argc == 0 then return true end
-      local info = debug.getinfo(2, "Sl")
-      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, format_func(arg))
+    if level ~= "OFF" then
+      log[level:lower()] = function(...)
+        local argc = select("#", ...)
+        if levelnr < current_log_level then return false end
+        if argc == 0 then return true end
+        if not open_logfile() then return false end
+        local info = debug.getinfo(2, "Sl")
+        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, format_func(arg))
+          end
         end
+        logfile:write(table.concat(parts, '\t'), "\n")
+        logfile:flush()
       end
-      logfile:write(table.concat(parts, '\t'), "\n")
-      logfile:flush()
     end
   end
 end