feat(health): fold successful healthchecks #22866

Problem:
checkhealth can be noisy, but we don't want to omit info.

Solution:
Fold OK results by default, if 'foldenable' is enabled.
Resolves #22796

runtime/doc/news.txt

@@ -106,6 +106,9 @@ The following changes to existing APIs or features add new behavior.
 • `:source` without arguments treats a buffer with its 'filetype' set to "lua"
   as Lua code regardless of its extension.
 
+• |:checkhealth| buffer now implements |folding|. The initial folding status is
+  defined by the 'foldenable' option.
+
 ==============================================================================
 REMOVED FEATURES                                                 *news-removed*
 

runtime/ftplugin/checkhealth.vim

@@ -9,6 +9,9 @@ endif
 runtime! ftplugin/help.vim
 
 setlocal wrap breakindent linebreak
+setlocal foldexpr=getline(v:lnum-1)=~'^=\\{78}$'?'>1':(getline(v:lnum)=~'^=\\{78}'?0:'=')
+setlocal foldmethod=expr
+setlocal foldtext=v:lua.require('vim.health').foldtext()
 let &l:iskeyword='!-~,^*,^|,^",192-255'
 
 if exists("b:undo_ftplugin")

runtime/lua/vim/health.lua

@@ -2,6 +2,40 @@ local M = {}
 
 local s_output = {}
 
+-- Returns the fold text of the current healthcheck section
+function M.foldtext()
+  local foldtext = vim.fn.foldtext()
+
+  if vim.bo.filetype ~= 'checkhealth' then
+    return foldtext
+  end
+
+  if vim.b.failedchecks == nil then
+    vim.b.failedchecks = vim.empty_dict()
+  end
+
+  if vim.b.failedchecks[foldtext] == nil then
+    local warning = '- WARNING '
+    local warninglen = string.len(warning)
+    local err = '- ERROR '
+    local errlen = string.len(err)
+    local failedchecks = vim.b.failedchecks
+    failedchecks[foldtext] = false
+
+    local foldcontent = vim.api.nvim_buf_get_lines(0, vim.v.foldstart - 1, vim.v.foldend, false)
+    for _, line in ipairs(foldcontent) do
+      if string.sub(line, 1, warninglen) == warning or string.sub(line, 1, errlen) == err then
+        failedchecks[foldtext] = true
+        break
+      end
+    end
+
+    vim.b.failedchecks = failedchecks
+  end
+
+  return vim.b.failedchecks[foldtext] and '+WE' .. foldtext:sub(4) or foldtext
+end
+
 -- From a path return a list [{name}, {func}, {type}] representing a healthcheck
 local function filepath_to_healthcheck(path)
   path = vim.fs.normalize(path)

test/functional/plugin/health_spec.lua

@@ -136,7 +136,7 @@ describe('health.vim', function()
         Bar = { foreground = Screen.colors.LightGrey, background = Screen.colors.DarkGrey },
       })
       command("checkhealth foo success1")
-      command("set nowrap laststatus=0")
+      command("set nofoldenable nowrap laststatus=0")
       screen:expect{grid=[[
         ^                                                  |
         {Bar:──────────────────────────────────────────────────}|
@@ -153,6 +153,22 @@ describe('health.vim', function()
       ]]}
     end)
 
+    it("fold healthchecks", function()
+      local screen = Screen.new(50, 7)
+      screen:attach()
+      command("checkhealth foo success1")
+      command("set nowrap laststatus=0")
+      screen:expect{grid=[[
+        ^                                                  |
+        ──────────────────────────────────────────────────|
+        +WE  4 lines: foo: ·······························|
+        ──────────────────────────────────────────────────|
+        +--  8 lines: test_plug.success1: require("test_pl|
+        ~                                                 |
+                                                          |
+      ]]}
+    end)
+
     it("gracefully handles invalid healthcheck", function()
       command("checkhealth non_existent_healthcheck")
       -- luacheck: ignore 613