fix(loader): reset hashes when running the loader

2 files changed, 49 insertions, 5 deletions

diff --git a/runtime/lua/vim/loader.lua b/runtime/lua/vim/loader.lua
index 38b1e9fc0f..7f953adc21 100644
--- a/runtime/lua/vim/loader.lua
+++ b/runtime/lua/vim/loader.lua
@@ -5,7 +5,7 @@ local loaders = package.loaders
 
 local M = {}
 
----@alias CacheHash {mtime: {sec:number, nsec:number}, size:number, type: string}
+---@alias CacheHash {mtime: {nsec: integer, sec: integer}, size: integer, type?: uv.aliases.fs_stat_types}
 ---@alias CacheEntry {hash:CacheHash, chunk:string}
 
 ---@class ModuleFindOpts
@@ -28,12 +28,11 @@ M.enabled = false
 ---@field _rtp string[]
 ---@field _rtp_pure string[]
 ---@field _rtp_key string
+---@field _hashes? table<string, CacheHash>
 local Loader = {
   VERSION = 3,
   ---@type table<string, table<string,ModuleInfo>>
   _indexed = {},
-  ---@type table<string, CacheHash>
-  _hashes = {},
   ---@type table<string, string[]>
   _topmods = {},
   _loadfile = loadfile,
@@ -44,9 +43,13 @@ local Loader = {
 }
 
 --- @param path string
---- @return uv.fs_stat.result
+--- @return CacheHash
 --- @private
 function Loader.get_hash(path)
+  if not Loader._hashes then
+    return uv.fs_stat(path) --[[@as CacheHash]]
+  end
+
   if not Loader._hashes[path] then
     -- Note we must never save a stat for a non-existent path.
     -- For non-existent paths fs_stat() will return nil.
@@ -163,13 +166,16 @@ end
 ---@return string|function
 ---@private
 function Loader.loader(modname)
+  Loader._hashes = {}
   local ret = M.find(modname)[1]
   if ret then
     -- Make sure to call the global loadfile so we respect any augmentations done elsewhere.
     -- E.g. profiling
     local chunk, err = loadfile(ret.modpath)
+    Loader._hashes = nil
     return chunk or error(err)
   end
+  Loader._hashes = nil
   return '\ncache_loader: module ' .. modname .. ' not found'
 end
 
@@ -373,7 +379,9 @@ function M.reset(path)
   end
 
   -- Path could be a directory so just clear all the hashes.
-  Loader._hashes = {}
+  if Loader._hashes then
+    Loader._hashes = {}
+  end
 end
 
 --- Enables the experimental Lua module loader:
diff --git a/test/functional/lua/loader_spec.lua b/test/functional/lua/loader_spec.lua
new file mode 100644
index 0000000000..e2958d1592
--- /dev/null
+++ b/test/functional/lua/loader_spec.lua
@@ -0,0 +1,36 @@
+-- Test suite for testing interactions with API bindings
+local helpers = require('test.functional.helpers')(after_each)
+
+local exec_lua = helpers.exec_lua
+local command = helpers.command
+local eq = helpers.eq
+
+describe('vim.loader', function()
+  before_each(helpers.clear)
+
+  it('handles changing files (#23027)', function()
+    exec_lua[[
+      vim.loader.enable()
+    ]]
+
+    local tmp = helpers.tmpname()
+    command('edit ' .. tmp)
+
+    eq(1, exec_lua([[
+      vim.api.nvim_buf_set_lines(0, 0, -1, true, {'_G.TEST=1'})
+      vim.cmd.write()
+      loadfile(...)()
+      return _G.TEST
+    ]], tmp))
+
+    -- fs latency
+    helpers.sleep(10)
+
+    eq(2, exec_lua([[
+      vim.api.nvim_buf_set_lines(0, 0, -1, true, {'_G.TEST=2'})
+      vim.cmd.write()
+      loadfile(...)()
+      return _G.TEST
+    ]], tmp))
+  end)
+end)