fix(lsp): revert buf_versions deprecation/replacement (#29217)

* Revert "fix(lsp): account for changedtick version gap on modified reset (#29170)"

This reverts commit 2e6d295f79.

* Revert "refactor(lsp): replace util.buf_versions with changedtick (#28943)"

This reverts commit 5c33815448.

test/functional/plugin/lsp_spec.lua

@@ -255,7 +255,7 @@ describe('LSP', function()
         return
       end
       local expected_handlers = {
-        { NIL, {}, { method = 'shutdown', bufnr = 1, client_id = 1, version = 2 } },
+        { NIL, {}, { method = 'shutdown', bufnr = 1, client_id = 1 } },
         { NIL, {}, { method = 'test', client_id = 1 } },
       }
       test_rpc_server {
@@ -948,11 +948,7 @@ describe('LSP', function()
     it('should forward ContentModified to callback', function()
       local expected_handlers = {
         { NIL, {}, { method = 'finish', client_id = 1 } },
-        {
-          { code = -32801 },
-          NIL,
-          { method = 'error_code_test', bufnr = 1, client_id = 1, version = 2 },
-        },
+        { { code = -32801 }, NIL, { method = 'error_code_test', bufnr = 1, client_id = 1 } },
       }
       local client --- @type vim.lsp.Client
       test_rpc_server {
@@ -982,7 +978,7 @@ describe('LSP', function()
     it('should track pending requests to the language server', function()
       local expected_handlers = {
         { NIL, {}, { method = 'finish', client_id = 1 } },
-        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1, version = 2 } },
+        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1 } },
       }
       local client --- @type vim.lsp.Client
       test_rpc_server {
@@ -1049,7 +1045,7 @@ describe('LSP', function()
     it('should clear pending and cancel requests on reply', function()
       local expected_handlers = {
         { NIL, {}, { method = 'finish', client_id = 1 } },
-        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1, version = 2 } },
+        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1 } },
       }
       local client --- @type vim.lsp.Client
       test_rpc_server {
@@ -1088,7 +1084,7 @@ describe('LSP', function()
     it('should trigger LspRequest autocmd when requests table changes', function()
       local expected_handlers = {
         { NIL, {}, { method = 'finish', client_id = 1 } },
-        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1, version = 2 } },
+        { NIL, {}, { method = 'slow_request', bufnr = 1, client_id = 1 } },
       }
       local client --- @type vim.lsp.Client
       test_rpc_server {
@@ -1368,7 +1364,6 @@ describe('LSP', function()
             },
             bufnr = 2,
             client_id = 1,
-            version = 2,
           },
         },
         { NIL, {}, { method = 'start', client_id = 1 } },
@@ -2122,6 +2117,7 @@ describe('LSP', function()
         local args = {...}
         local bufnr = select(1, ...)
         local text_edit = select(2, ...)
+        vim.lsp.util.buf_versions[bufnr] = 10
         vim.lsp.util.apply_text_document_edit(text_edit, nil, 'utf-16')
       ]],
         target_bufnr,
@@ -2133,13 +2129,16 @@ describe('LSP', function()
       }, buf_lines(target_bufnr))
     end)
     it('skips the edit if the version of the edit is behind the local buffer ', function()
-      local apply_edit_mocking_current_version = function(edit)
+      local apply_edit_mocking_current_version = function(edit, versionedBuf)
         exec_lua(
           [[
           local args = {...}
+          local versionedBuf = args[2]
+          vim.lsp.util.buf_versions[versionedBuf.bufnr] = versionedBuf.currentVersion
           vim.lsp.util.apply_text_document_edit(args[1], nil, 'utf-16')
         ]],
-          edit
+          edit,
+          versionedBuf
         )
       end
 
@@ -2151,17 +2150,17 @@ describe('LSP', function()
       eq(baseText, buf_lines(target_bufnr))
 
       -- Apply an edit for an old version, should skip
-      apply_edit_mocking_current_version(text_document_edit(1))
+      apply_edit_mocking_current_version(
+        text_document_edit(2),
+        { currentVersion = 7, bufnr = target_bufnr }
+      )
       eq(baseText, buf_lines(target_bufnr)) -- no change
 
       -- Sanity check that next version to current does apply change
-      apply_edit_mocking_current_version(text_document_edit(exec_lua(
-        [[
-          local bufnr = ...
-          return vim.b[bufnr].changedtick
-        ]],
-        target_bufnr
-      )))
+      apply_edit_mocking_current_version(
+        text_document_edit(8),
+        { currentVersion = 7, bufnr = target_bufnr }
+      )
       eq({
         'First ↥ 🤦 🦄 line of text',
         '2nd line of 语text',
@@ -2240,6 +2239,18 @@ describe('LSP', function()
         }
 
         vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+
+        local update_changed_tick = function()
+          vim.lsp.util.buf_versions[bufnr] = vim.api.nvim_buf_get_var(bufnr, 'changedtick')
+        end
+
+        update_changed_tick()
+        vim.api.nvim_buf_attach(bufnr, false, {
+          on_changedtick = function()
+            update_changed_tick()
+          end
+        })
+
         return {bufnr, vim.api.nvim_buf_get_var(bufnr, 'changedtick')}
       ]]