feat(lsp): use fuzzy match on filterText instead of prefix match

The `complete()` mechanism matches completion candidates against
the typed text, so strict pre-filtering isn't necessary.

This is a first step towards supporting postfix snippets (like
`items@insert` in luals)

2 files changed, 11 insertions, 5 deletions

diff --git a/runtime/lua/vim/lsp/completion.lua b/runtime/lua/vim/lsp/completion.lua
index 25b3d53c8c..f9b0563b86 100644
--- a/runtime/lua/vim/lsp/completion.lua
+++ b/runtime/lua/vim/lsp/completion.lua
@@ -201,11 +201,17 @@ function M._lsp_to_complete_items(result, prefix, client_id)
     return {}
   end
 
-  local function matches_prefix(item)
-    return vim.startswith(get_completion_word(item), prefix)
-  end
+  if prefix ~= '' then
+    ---@param item lsp.CompletionItem
+    local function match_prefix(item)
+      if item.filterText then
+        return next(vim.fn.matchfuzzy({ item.filterText }, prefix))
+      end
+      return true
+    end
 
-  items = vim.tbl_filter(matches_prefix, items) --[[@as lsp.CompletionItem[]|]]
+    items = vim.tbl_filter(match_prefix, items) --[[@as lsp.CompletionItem[]|]]
+  end
   table.sort(items, function(a, b)
     return (a.sortText or a.label) < (b.sortText or b.label)
   end)
diff --git a/test/functional/plugin/lsp/completion_spec.lua b/test/functional/plugin/lsp/completion_spec.lua
index 5b7232ad7e..078abdf653 100644
--- a/test/functional/plugin/lsp/completion_spec.lua
+++ b/test/functional/plugin/lsp/completion_spec.lua
@@ -228,7 +228,7 @@ describe('vim.lsp.completion: item conversion', function()
           },
         },
         {
-          filterText = 'notthis_thread',
+          filterText = 'no_match',
           insertText = 'notthis_thread',
           insertTextFormat = 1,
           kind = 9,