Merge remote-tracking branch 'upstream/master' into mix_20240309HEADrahm

11 files changed, 1169 insertions, 179 deletions

diff --git a/test/functional/plugin/health_spec.lua b/test/functional/plugin/health_spec.lua
index 753da64522..406b5c3c16 100644
--- a/test/functional/plugin/health_spec.lua
+++ b/test/functional/plugin/health_spec.lua
@@ -66,6 +66,18 @@ describe(':checkhealth', function()
     eq({}, getcompletion('', 'checkhealth'))
     assert_alive()
   end)
+
+  it('vim.g.health', function()
+    clear()
+    command("let g:health = {'style':'float'}")
+    command('checkhealth lsp')
+    eq(
+      'editor',
+      exec_lua([[
+      return vim.api.nvim_win_get_config(0).relative
+    ]])
+    )
+  end)
 end)
 
 describe('vim.health', function()
diff --git a/test/functional/plugin/lsp/completion_spec.lua b/test/functional/plugin/lsp/completion_spec.lua
index 39b6ddc105..4e90c2fd1b 100644
--- a/test/functional/plugin/lsp/completion_spec.lua
+++ b/test/functional/plugin/lsp/completion_spec.lua
@@ -216,6 +216,43 @@ describe('vim.lsp.completion: item conversion', function()
       })
     end)
 
+    it('uses filterText as word if label/newText would not match', function()
+      local items = {
+        {
+          filterText = '<module',
+          insertTextFormat = 2,
+          kind = 10,
+          label = 'module',
+          sortText = 'module',
+          textEdit = {
+            newText = '<module>$1</module>$0',
+            range = {
+              start = {
+                character = 0,
+                line = 0,
+              },
+              ['end'] = {
+                character = 0,
+                line = 0,
+              },
+            },
+          },
+        },
+      }
+      assert_completion_matches('<mo', items, {
+        {
+          abbr = 'module',
+          word = '<module',
+        },
+      })
+      assert_completion_matches('', items, {
+        {
+          abbr = 'module',
+          word = 'module',
+        },
+      })
+    end)
+
     it('fuzzy matches on label when filterText is missing', function()
       assert_completion_matches('fo', {
         { label = 'foo' },
@@ -731,9 +768,10 @@ describe('vim.lsp.completion: item conversion', function()
   )
 end)
 
+--- @param name string
 --- @param completion_result lsp.CompletionList
 --- @return integer
-local function create_server(completion_result)
+local function create_server(name, completion_result)
   return exec_lua(function()
     local server = _G._create_server({
       capabilities = {
@@ -751,7 +789,7 @@ local function create_server(completion_result)
     local bufnr = vim.api.nvim_get_current_buf()
     vim.api.nvim_win_set_buf(0, bufnr)
     return vim.lsp.start({
-      name = 'dummy',
+      name = name,
       cmd = server.cmd,
       on_attach = function(client, bufnr0)
         vim.lsp.completion.enable(true, client.id, bufnr0, {
@@ -800,7 +838,7 @@ describe('vim.lsp.completion: protocol', function()
   end
 
   it('fetches completions and shows them using complete on trigger', function()
-    create_server({
+    create_server('dummy', {
       isIncomplete = false,
       items = {
         {
@@ -892,7 +930,7 @@ describe('vim.lsp.completion: protocol', function()
   end)
 
   it('merges results from multiple clients', function()
-    create_server({
+    create_server('dummy1', {
       isIncomplete = false,
       items = {
         {
@@ -900,7 +938,7 @@ describe('vim.lsp.completion: protocol', function()
         },
       },
     })
-    create_server({
+    create_server('dummy2', {
       isIncomplete = false,
       items = {
         {
@@ -933,7 +971,7 @@ describe('vim.lsp.completion: protocol', function()
         },
       },
     }
-    local client_id = create_server(completion_list)
+    local client_id = create_server('dummy', completion_list)
 
     exec_lua(function()
       _G.called = false
@@ -970,7 +1008,7 @@ describe('vim.lsp.completion: protocol', function()
   end)
 
   it('enable(…,{convert=fn}) custom word/abbr format', function()
-    create_server({
+    create_server('dummy', {
       isIncomplete = false,
       items = {
         {
@@ -1012,7 +1050,7 @@ describe('vim.lsp.completion: integration', function()
     exec_lua(function()
       vim.o.completeopt = 'menuone,noselect'
     end)
-    create_server(completion_list)
+    create_server('dummy', completion_list)
     feed('i world<esc>0ih<c-x><c-o>')
     retry(nil, nil, function()
       eq(
diff --git a/test/functional/plugin/lsp/diagnostic_spec.lua b/test/functional/plugin/lsp/diagnostic_spec.lua
index 5afbe22793..4ecb056d01 100644
--- a/test/functional/plugin/lsp/diagnostic_spec.lua
+++ b/test/functional/plugin/lsp/diagnostic_spec.lua
@@ -89,7 +89,7 @@ describe('vim.lsp.diagnostic', function()
         return extmarks
       end
 
-      client_id = assert(vim.lsp.start_client {
+      client_id = assert(vim.lsp.start({
         cmd_env = {
           NVIM_LUA_NOTRACK = '1',
         },
@@ -101,7 +101,7 @@ describe('vim.lsp.diagnostic', function()
           '--headless',
         },
         offset_encoding = 'utf-16',
-      })
+      }, { attach = false }))
     end)
 
     fake_uri = 'file:///fake/uri'
@@ -209,10 +209,16 @@ describe('vim.lsp.diagnostic', function()
     before_each(function()
       exec_lua(create_server_definition)
       exec_lua(function()
+        _G.requests = 0
         _G.server = _G._create_server({
           capabilities = {
             diagnosticProvider = {},
           },
+          handlers = {
+            [vim.lsp.protocol.Methods.textDocument_diagnostic] = function()
+              _G.requests = _G.requests + 1
+            end,
+          },
         })
 
         function _G.get_extmarks(bufnr, client_id0)
@@ -373,5 +379,56 @@ describe('vim.lsp.diagnostic', function()
         end)
       )
     end)
+
+    it('handles server cancellation', function()
+      eq(
+        1,
+        exec_lua(function()
+          vim.lsp.diagnostic.on_diagnostic({
+            code = vim.lsp.protocol.ErrorCodes.ServerCancelled,
+            -- Empty data defaults to retriggering request
+            data = {},
+            message = '',
+          }, {}, {
+            method = vim.lsp.protocol.Methods.textDocument_diagnostic,
+            client_id = client_id,
+          })
+
+          return _G.requests
+        end)
+      )
+
+      eq(
+        2,
+        exec_lua(function()
+          vim.lsp.diagnostic.on_diagnostic({
+            code = vim.lsp.protocol.ErrorCodes.ServerCancelled,
+            data = { retriggerRequest = true },
+            message = '',
+          }, {}, {
+            method = vim.lsp.protocol.Methods.textDocument_diagnostic,
+            client_id = client_id,
+          })
+
+          return _G.requests
+        end)
+      )
+
+      eq(
+        2,
+        exec_lua(function()
+          vim.lsp.diagnostic.on_diagnostic({
+            code = vim.lsp.protocol.ErrorCodes.ServerCancelled,
+            data = { retriggerRequest = false },
+            message = '',
+          }, {}, {
+            method = vim.lsp.protocol.Methods.textDocument_diagnostic,
+            client_id = client_id,
+          })
+
+          return _G.requests
+        end)
+      )
+    end)
   end)
 end)
diff --git a/test/functional/plugin/lsp/folding_range_spec.lua b/test/functional/plugin/lsp/folding_range_spec.lua
new file mode 100644
index 0000000000..7e68a598d2
--- /dev/null
+++ b/test/functional/plugin/lsp/folding_range_spec.lua
@@ -0,0 +1,647 @@
+local t = require('test.testutil')
+local n = require('test.functional.testnvim')()
+local Screen = require('test.functional.ui.screen')
+local t_lsp = require('test.functional.plugin.lsp.testutil')
+
+local eq = t.eq
+local tempname = t.tmpname
+
+local clear_notrace = t_lsp.clear_notrace
+local create_server_definition = t_lsp.create_server_definition
+
+local api = n.api
+local exec_lua = n.exec_lua
+local insert = n.insert
+local command = n.command
+local feed = n.feed
+
+describe('vim.lsp.folding_range', function()
+  local text = [[// foldLevel() {{{2
+/// @return  fold level at line number "lnum" in the current window.
+static int foldLevel(linenr_T lnum)
+{
+  // While updating the folds lines between invalid_top and invalid_bot have
+  // an undefined fold level.  Otherwise update the folds first.
+  if (invalid_top == 0) {
+    checkupdate(curwin);
+  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {
+    return prev_lnum_lvl;
+  } else if (lnum >= invalid_top && lnum <= invalid_bot) {
+    return -1;
+  }
+
+  // Return quickly when there is no folding at all in this window.
+  if (!hasAnyFolding(curwin)) {
+    return 0;
+  }
+
+  return foldLevelWin(curwin, lnum);
+}]]
+
+  local result = {
+    {
+      endLine = 19,
+      kind = 'region',
+      startCharacter = 1,
+      startLine = 3,
+    },
+    {
+      endCharacter = 2,
+      endLine = 7,
+      kind = 'region',
+      startCharacter = 25,
+      startLine = 6,
+    },
+    {
+      endCharacter = 2,
+      endLine = 9,
+      kind = 'region',
+      startCharacter = 55,
+      startLine = 8,
+    },
+    {
+      endCharacter = 2,
+      endLine = 11,
+      kind = 'region',
+      startCharacter = 58,
+      startLine = 10,
+    },
+    {
+      endCharacter = 2,
+      endLine = 16,
+      kind = 'region',
+      startCharacter = 31,
+      startLine = 15,
+    },
+    {
+      endCharacter = 68,
+      endLine = 1,
+      kind = 'comment',
+      startCharacter = 2,
+      startLine = 0,
+    },
+    {
+      endCharacter = 64,
+      endLine = 5,
+      kind = 'comment',
+      startCharacter = 4,
+      startLine = 4,
+    },
+  }
+
+  local bufnr ---@type integer
+  local client_id ---@type integer
+
+  clear_notrace()
+  before_each(function()
+    clear_notrace()
+
+    exec_lua(create_server_definition)
+    bufnr = n.api.nvim_get_current_buf()
+    client_id = exec_lua(function()
+      _G.server = _G._create_server({
+        capabilities = {
+          foldingRangeProvider = true,
+        },
+        handlers = {
+          ['textDocument/foldingRange'] = function(_, _, callback)
+            callback(nil, result)
+          end,
+        },
+      })
+
+      vim.api.nvim_win_set_buf(0, bufnr)
+
+      return vim.lsp.start({ name = 'dummy', cmd = _G.server.cmd })
+    end)
+    command('set foldmethod=expr foldcolumn=1 foldlevel=999')
+    insert(text)
+  end)
+  after_each(function()
+    api.nvim_exec_autocmds('VimLeavePre', { modeline = false })
+  end)
+
+  describe('setup()', function()
+    ---@type integer
+    local bufnr_set_expr
+    ---@type integer
+    local bufnr_never_set_expr
+
+    local function buf_autocmd_num(bufnr_to_check)
+      return exec_lua(function()
+        return #vim.api.nvim_get_autocmds({ buffer = bufnr_to_check, event = 'LspNotify' })
+      end)
+    end
+
+    before_each(function()
+      command([[setlocal foldexpr=v:lua.vim.lsp.foldexpr()]])
+      exec_lua(function()
+        bufnr_set_expr = vim.api.nvim_create_buf(true, false)
+        vim.api.nvim_set_current_buf(bufnr_set_expr)
+      end)
+      insert(text)
+      command('write ' .. tempname(false))
+      command([[setlocal foldexpr=v:lua.vim.lsp.foldexpr()]])
+      exec_lua(function()
+        bufnr_never_set_expr = vim.api.nvim_create_buf(true, false)
+        vim.api.nvim_set_current_buf(bufnr_never_set_expr)
+      end)
+      insert(text)
+      api.nvim_win_set_buf(0, bufnr_set_expr)
+    end)
+
+    it('only create event hooks where foldexpr has been set', function()
+      eq(1, buf_autocmd_num(bufnr))
+      eq(1, buf_autocmd_num(bufnr_set_expr))
+      eq(0, buf_autocmd_num(bufnr_never_set_expr))
+    end)
+
+    it('does not create duplicate event hooks after reloaded', function()
+      command('edit')
+      eq(1, buf_autocmd_num(bufnr_set_expr))
+    end)
+
+    it('cleans up event hooks when buffer is unloaded', function()
+      command('bdelete')
+      eq(0, buf_autocmd_num(bufnr_set_expr))
+    end)
+  end)
+
+  describe('expr()', function()
+    --- @type test.functional.ui.screen
+    local screen
+    before_each(function()
+      screen = Screen.new(80, 45)
+      screen:set_default_attr_ids({
+        [1] = { background = Screen.colors.Grey, foreground = Screen.colors.DarkBlue },
+        [2] = { bold = true, foreground = Screen.colors.Blue1 },
+        [3] = { bold = true, reverse = true },
+        [4] = { reverse = true },
+      })
+      command([[set foldexpr=v:lua.vim.lsp.foldexpr()]])
+      command([[split]])
+    end)
+
+    it('can compute fold levels', function()
+      ---@type table<integer, string>
+      local foldlevels = {}
+      for i = 1, 21 do
+        foldlevels[i] = exec_lua('return vim.lsp.foldexpr(' .. i .. ')')
+      end
+      eq({
+        [1] = '>1',
+        [2] = '<1',
+        [3] = '0',
+        [4] = '>1',
+        [5] = '>2',
+        [6] = '<2',
+        [7] = '>2',
+        [8] = '<2',
+        [9] = '>2',
+        [10] = '<2',
+        [11] = '>2',
+        [12] = '<2',
+        [13] = '1',
+        [14] = '1',
+        [15] = '1',
+        [16] = '>2',
+        [17] = '<2',
+        [18] = '1',
+        [19] = '1',
+        [20] = '<1',
+        [21] = '0',
+      }, foldlevels)
+    end)
+
+    it('updates folds in all windows', function()
+      screen:expect({
+        grid = [[
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }^}                                                                              |
+{3:[No Name] [+]                                                                   }|
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{4:[No Name] [+]                                                                   }|
+                                                                                |
+  ]],
+      })
+    end)
+
+    it('persists wherever foldexpr is set', function()
+      command([[setlocal foldexpr=]])
+      feed('<C-w><C-w>zx')
+      screen:expect({
+        grid = [[
+{1: }// foldLevel() {{{2                                                            |
+{1: }/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1: }{                                                                              |
+{1: }  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1: }  // an undefined fold level.  Otherwise update the folds first.               |
+{1: }  if (invalid_top == 0) {                                                      |
+{1: }    checkupdate(curwin);                                                       |
+{1: }  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1: }    return prev_lnum_lvl;                                                      |
+{1: }  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1: }    return -1;                                                                 |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  // Return quickly when there is no folding at all in this window.            |
+{1: }  if (!hasAnyFolding(curwin)) {                                                |
+{1: }    return 0;                                                                  |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{4:[No Name] [+]                                                                   }|
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }^}                                                                              |
+{3:[No Name] [+]                                                                   }|
+                                                                                |
+  ]],
+      })
+    end)
+
+    it('synchronizes changed rows with their previous foldlevels', function()
+      command('1,2d')
+      screen:expect({
+        grid = [[
+{1: }^static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{2:~                                                                               }|*2
+{3:[No Name] [+]                                                                   }|
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{2:~                                                                               }|*2
+{4:[No Name] [+]                                                                   }|
+                                                                                |
+]],
+      })
+    end)
+
+    it('clears folds when sole client detaches', function()
+      exec_lua(function()
+        vim.lsp.buf_detach_client(bufnr, client_id)
+      end)
+      screen:expect({
+        grid = [[
+{1: }// foldLevel() {{{2                                                            |
+{1: }/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1: }{                                                                              |
+{1: }  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1: }  // an undefined fold level.  Otherwise update the folds first.               |
+{1: }  if (invalid_top == 0) {                                                      |
+{1: }    checkupdate(curwin);                                                       |
+{1: }  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1: }    return prev_lnum_lvl;                                                      |
+{1: }  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1: }    return -1;                                                                 |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  // Return quickly when there is no folding at all in this window.            |
+{1: }  if (!hasAnyFolding(curwin)) {                                                |
+{1: }    return 0;                                                                  |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  return foldLevelWin(curwin, lnum);                                           |
+{1: }^}                                                                              |
+{3:[No Name] [+]                                                                   }|
+{1: }// foldLevel() {{{2                                                            |
+{1: }/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1: }{                                                                              |
+{1: }  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1: }  // an undefined fold level.  Otherwise update the folds first.               |
+{1: }  if (invalid_top == 0) {                                                      |
+{1: }    checkupdate(curwin);                                                       |
+{1: }  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1: }    return prev_lnum_lvl;                                                      |
+{1: }  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1: }    return -1;                                                                 |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  // Return quickly when there is no folding at all in this window.            |
+{1: }  if (!hasAnyFolding(curwin)) {                                                |
+{1: }    return 0;                                                                  |
+{1: }  }                                                                            |
+{1: }                                                                               |
+{1: }  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{4:[No Name] [+]                                                                   }|
+                                                                                |
+  ]],
+      })
+    end)
+
+    it('remains valid after the client re-attaches.', function()
+      exec_lua(function()
+        vim.lsp.buf_detach_client(bufnr, client_id)
+        vim.lsp.buf_attach_client(bufnr, client_id)
+      end)
+      screen:expect({
+        grid = [[
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }^}                                                                              |
+{3:[No Name] [+]                                                                   }|
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{                                                                              |
+{1:-}  // While updating the folds lines between invalid_top and invalid_bot have   |
+{1:2}  // an undefined fold level.  Otherwise update the folds first.               |
+{1:-}  if (invalid_top == 0) {                                                      |
+{1:2}    checkupdate(curwin);                                                       |
+{1:-}  } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {                        |
+{1:2}    return prev_lnum_lvl;                                                      |
+{1:-}  } else if (lnum >= invalid_top && lnum <= invalid_bot) {                     |
+{1:2}    return -1;                                                                 |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  // Return quickly when there is no folding at all in this window.            |
+{1:-}  if (!hasAnyFolding(curwin)) {                                                |
+{1:2}    return 0;                                                                  |
+{1:│}  }                                                                            |
+{1:│}                                                                               |
+{1:│}  return foldLevelWin(curwin, lnum);                                           |
+{1: }}                                                                              |
+{4:[No Name] [+]                                                                   }|
+                                                                                |
+  ]],
+      })
+    end)
+  end)
+
+  describe('foldtext()', function()
+    --- @type test.functional.ui.screen
+    local screen
+    before_each(function()
+      screen = Screen.new(80, 23)
+      screen:set_default_attr_ids({
+        [1] = { background = Screen.colors.Grey, foreground = Screen.colors.DarkBlue },
+        [2] = { foreground = Screen.colors.DarkBlue, background = Screen.colors.LightGrey },
+        [3] = { bold = true, foreground = Screen.colors.Blue1 },
+        [4] = { bold = true, reverse = true },
+        [5] = { reverse = true },
+      })
+      command(
+        [[set foldexpr=v:lua.vim.lsp.foldexpr() foldtext=v:lua.vim.lsp.foldtext() foldlevel=1]]
+      )
+    end)
+
+    it('shows the first folded line if `collapsedText` does not exist', function()
+      screen:expect({
+        grid = [[
+{1:-}// foldLevel() {{{2                                                            |
+{1:│}/// @return  fold level at line number "lnum" in the current window.           |
+{1: }static int foldLevel(linenr_T lnum)                                            |
+{1:-}{