perf: improve for source providing huge list of items (#1980)

* perf: avoid creating closure in cache.ensure and drop some cached getters

This mainly addresses the perf issue on large amount of calls to
`entry.new`. Previously every `cache.ensure` calls in the code path of
it creates an anonymous function, and it seems that luajit just could
not inline it. Function creation is not expensive in luajit, but that
overhead is noticeable if every `cache.ensure` call creates a function.
The first improvemnt is to solidate the cache callback and attach it to
the metatable of `entry`. This ensures that every created entry instance
share the same cache callback and no new functions will be frequently created,
reduces the ram usage and GC overhead.

To improve it further, some frequently accessed fields of entry like
`completion_item` and `offset` is refactored to use simple table access
instead of getter pattern. The current cached getter is implemented
using `cache.ensure`, which introduces two more levels of function calls
on each access: `cache.key` and `cache.get`. The overhead is okay if but
noticeable if entries amount is quite large: you need to call 4 functions on
a simple `completion_item` field access for each item.

All of the changes done in the commit is just constant time
optimization. But the different is huge if tested with LS providing
large amount of entries like tailwindcss.

* perf: delay fuzzy match on displayed vim item

`entry.get_vim_item` is a very heavy call, especially when user do
complex stuff on item formatting. Delay its call to window displaying to
let `performance.max_view_entries` applied to it.

* remove unneeded fill_defaults

* update gha

---------

Co-authored-by: hrsh7th <629908+hrsh7th@users.noreply.github.com>

lua/cmp/source.lua

@@ -24,6 +24,9 @@ local char = require('cmp.utils.char')
 ---@field public completion_context lsp.CompletionContext|nil
 ---@field public status cmp.SourceStatus
 ---@field public complete_dedup function
+---@field public default_replace_range lsp.Range
+---@field public default_insert_range lsp.Range
+---@field public position_encoding lsp.PositionEncodingKind
 local source = {}
 
 ---@alias cmp.SourceStatus 1 | 2 | 3
@@ -41,6 +44,7 @@ source.new = function(name, s)
   self.cache = cache.new()
   self.complete_dedup = async.dedup()
   self.revision = 0
+  self.position_encoding = self:get_position_encoding_kind()
   self:reset()
   return self
 end
@@ -108,7 +112,7 @@ source.get_entries = function(self, ctx)
   local entries = {}
   local matching_config = self:get_matching_config()
   for _, e in ipairs(target_entries) do
-    local o = e:get_offset()
+    local o = e.offset
     if not inputs[o] then
       inputs[o] = string.sub(ctx.cursor_before_line, o)
     end
@@ -118,7 +122,7 @@ source.get_entries = function(self, ctx)
     e.exact = false
     if e.score >= 1 then
       e.matches = match.matches
-      e.exact = e:get_filter_text() == inputs[o] or e:get_word() == inputs[o]
+      e.exact = e.filter_text == inputs[o] or e.word == inputs[o]
 
       if entry_filter(e, ctx) then
         entries[#entries + 1] = e
@@ -138,46 +142,46 @@ source.get_entries = function(self, ctx)
 end
 
 ---Get default insert range (UTF8 byte index).
+---@package
 ---@return lsp.Range
-source.get_default_insert_range = function(self)
-  if not self.context then
-    error('context is not initialized yet.')
-  end
-
-  return self.cache:ensure({ 'get_default_insert_range', tostring(self.revision) }, function()
-    return {
-      start = {
-        line = self.context.cursor.row - 1,
-        character = self.offset - 1,
-      },
-      ['end'] = {
-        line = self.context.cursor.row - 1,
-        character = self.context.cursor.col - 1,
-      },
-    }
-  end)
+source._get_default_insert_range = function(self)
+  return {
+    start = {
+      line = self.context.cursor.row - 1,
+      character = self.offset - 1,
+    },
+    ['end'] = {
+      line = self.context.cursor.row - 1,
+      character = self.context.cursor.col - 1,
+    },
+  }
 end
 
 ---Get default replace range (UTF8 byte index).
+---@package
 ---@return lsp.Range
-source.get_default_replace_range = function(self)
-  if not self.context then
-    error('context is not initialized yet.')
-  end
+source._get_default_replace_range = function(self)
+  local _, e = pattern.offset('^' .. '\\%(' .. self:get_keyword_pattern() .. '\\)', string.sub(self.context.cursor_line, self.offset))
+  return {
+    start = {
+      line = self.context.cursor.row - 1,
+      character = self.offset,
+    },
+    ['end'] = {
+      line = self.context.cursor.row - 1,
+      character = (e and self.offset + e - 2 or self.context.cursor.col - 1),
+    },
+  }
+end
 
-  return self.cache:ensure({ 'get_default_replace_range', tostring(self.revision) }, function()
-    local _, e = pattern.offset('^' .. '\\%(' .. self:get_keyword_pattern() .. '\\)', string.sub(self.context.cursor_line, self.offset))
-    return {
-      start = {
-        line = self.context.cursor.row - 1,
-        character = self.offset,
-      },
-      ['end'] = {
-        line = self.context.cursor.row - 1,
-        character = (e and self.offset + e - 2 or self.context.cursor.col - 1),
-      },
-    }
-  end)
+---@deprecated use source.default_insert_range instead
+source.get_default_insert_range = function(self)
+  return self.default_insert_range
+end
+
+---@deprecated use source.default_replace_range instead
+source.get_default_replae_range = function(self)
+  return self.default_replace_range
 end
 
 ---Return source name.
@@ -322,6 +326,9 @@ source.complete = function(self, ctx, callback)
   self.offset = offset
   self.request_offset = offset
   self.context = ctx
+  self.default_replace_range = self:_get_default_replace_range()
+  self.default_insert_range = self:_get_default_insert_range()
+  self.position_encoding = self:get_position_encoding_kind()
   self.completion_context = completion_context
   self.source:complete(
     vim.tbl_extend('keep', misc.copy(self:get_source_config()), {
@@ -346,11 +353,11 @@ source.complete = function(self, ctx, callback)
         self.status = source.SourceStatus.COMPLETED
         self.entries = {}
         for _, item in ipairs(response.items or response) do
-          if (item or {}).label then
+          if item.label then
             local e = entry.new(ctx, self, item, response.itemDefaults)
             if not e:is_invalid() then
               table.insert(self.entries, e)
-              self.offset = math.min(self.offset, e:get_offset())
+              self.offset = math.min(self.offset, e.offset)
             end
           end
         end