feat: lsp diagnostics and prefiltering by entry attribute (#543)

prefiltering for lsp_document_symbols and lsp_workspace_symbols.
example: type `:var:` to show all vars

lua/telescope/sorters.lua

@@ -39,6 +39,7 @@ function Sorter:new(opts)
 
   return setmetatable({
     state = {},
+    filter_function = opts.filter_function,
     scoring_function = opts.scoring_function,
     highlighter = opts.highlighter,
     discard = opts.discard,
@@ -84,7 +85,13 @@ function Sorter:score(prompt, entry)
     return FILTERED
   end
 
-  local score = self:scoring_function(prompt or "", ordinal, entry)
+  local filter_score
+  if self.filter_function ~= nil then
+    filter_score, prompt = self:filter_function(prompt, entry)
+  end
+
+  local score = (filter_score == FILTERED and FILTERED or
+    self:scoring_function(prompt or "", ordinal, entry))
 
   if score == FILTERED then
     self:_mark_discarded(prompt, ordinal)
@@ -467,4 +474,45 @@ sorters.get_substr_matcher = function()
   }
 end
 
+local substr_matcher = function(_, prompt, line, _)
+  local display = line:lower()
+  local search_terms = util.max_split(prompt, "%s")
+  local matched = 0
+  local total_search_terms = 0
+  for _, word in pairs(search_terms) do
+    total_search_terms = total_search_terms + 1
+    if display:find(word, 1, true) then
+      matched = matched + 1
+    end
+  end
+
+  return matched == total_search_terms and 0 or FILTERED
+end
+
+local filter_function = function(opts)
+  local scoring_function = vim.F.if_nil(opts.filter_function, substr_matcher)
+  local tag = vim.F.if_nil(opts.tag, "ordinal")
+  local delimiter = vim.F.if_nil(opts.delimiter, ":")
+
+  return function(_, prompt, entry)
+    local filter = "^(" .. delimiter .. "(%S+)" .. "[" .. delimiter .. "%s]" .. ")"
+    local matched = prompt:match(filter)
+
+    if matched == nil then
+      return 0, prompt
+    end
+    -- clear prompt of tag
+    prompt = prompt:sub(#matched + 1, -1)
+    local query = vim.trim(matched:gsub(delimiter, ""))
+    return scoring_function(_, query, entry[tag], _), prompt
+  end
+end
+
+sorters.prefilter = function(opts)
+  local sorter = opts.sorter
+  sorter.filter_function = filter_function(opts)
+  sorter._was_discarded = function() return false end
+  return sorter
+end
+
 return sorters