perf(source): cache filtered entries for current context

lua/cmp/source.lua

@@ -18,6 +18,7 @@ local char = require('cmp.utils.char')
 ---@field public incomplete boolean
 ---@field public is_triggered_by_symbol boolean
 ---@field public entries cmp.Entry[]
+---@field public filtered {entries: cmp.Entry[], ctx: cmp.Context}
 ---@field public offset integer
 ---@field public request_offset integer
 ---@field public context cmp.Context
@@ -53,6 +54,7 @@ source.reset = function(self)
   self.is_triggered_by_symbol = false
   self.incomplete = false
   self.entries = {}
+  self.filtered = {}
   self.offset = -1
   self.request_offset = -1
   self.completion_context = nil
@@ -88,6 +90,10 @@ source.get_entries = function(self, ctx)
     return {}
   end
 
+  if self.filtered.ctx and self.filtered.ctx.id == ctx.id then
+    return self.filtered.entries
+  end
+
   local entry_filter = self:get_entry_filter()
 
   local inputs = {}
@@ -116,6 +122,7 @@ source.get_entries = function(self, ctx)
       end
     end
   end
+  self.filtered = { entries = entries, ctx = ctx }
   return entries
 end