fix: add fs.joinpath to work in v0.9.0 (#118)

* test: work tests for async_finder

I noticed these tests do not work because of vim.fs.joinpath lacking. I
will enable these tests and fix the bug.

* feat: implement vim.fs.joinpath to work in v0.9.0

lua/frecency/async_finder.lua

@@ -36,12 +36,12 @@ AsyncFinder.new = function(fs, path, entry_maker, initial_results)
       if self.closed then
         break
       end
-      local fullpath = vim.fs.joinpath(path, name)
+      local fullpath = fs:joinpath(path, name)
       if not seen[fullpath] then
         seen[fullpath] = true
         index = index + 1
         count = count + 1
-        local entry = entry_maker { id = 0, count = 0, path = vim.fs.joinpath(path, name), score = 0 }
+        local entry = entry_maker { id = 0, count = 0, path = fs:joinpath(path, name), score = 0 }
         if entry then
           entry.index = index
           table.insert(self.entries, entry)

lua/frecency/fs.lua

@@ -29,6 +29,19 @@ FS.new = function(config)
   return self
 end
 
+---This is needed for Neovim v0.9.0.
+---@param ... string
+---@return string
+function FS:joinpath(...)
+  if vim.fs.joinpath then
+    return vim.fs.joinpath(...)
+  end
+  local function join_paths(...)
+    return (table.concat({ ... }, "/"):gsub("//+", "/"))
+  end
+  return join_paths(...)
+end
+
 ---@param path string
 ---@return boolean
 function FS:is_valid_path(path)
@@ -45,13 +58,13 @@ function FS:scan_dir(path)
       vim.fs.dir(path, {
         depth = self.config.scan_depth,
         skip = function(dirname)
-          if self:is_ignored(vim.fs.joinpath(path, dirname)) then
+          if self:is_ignored(self:joinpath(path, dirname)) then
             return false
           end
         end,
       })
     do
-      local fullpath = vim.fs.joinpath(path, name)
+      local fullpath = self:joinpath(path, name)
       if type == "file" and not self:is_ignored(fullpath) and gitignore({ path }, fullpath) then
         coroutine.yield(name)
       end

lua/frecency/tests/async_finder_spec.lua

@@ -28,14 +28,6 @@ local function with_files(files, initial_results, callback)
 end
 
 describe("async_finder", function()
-  ---@diagnostic disable-next-line: param-type-mismatch
-  if vim.version.eq(vim.version(), "0.9.0") then
-    it("skips these tests for v0.9.0", function()
-      assert.are.same(true, true)
-    end)
-    return
-  end
-
   local function run(async_finder)
     local count = { process_result = 0, process_complete = 0 }
     local results = {}