feat(checkhealth): trigger FileType event after showing report

Problem:
`FileType` event is fired before checkhealth report is finished, so
user can't override report settings or contents.
https://github.com/neovim/neovim/pull/33172#issuecomment-2833513916

Solution:
- Trigger FileType event later.
- Document how to remove emojis.

runtime/doc/health.txt

@@ -9,18 +9,18 @@
 ==============================================================================
 Checkhealth                                              *vim.health* *health*
 
-
 vim.health is a minimal framework to help users troubleshoot configuration and
 any other environment conditions that a plugin might care about. Nvim ships
 with healthchecks for configuration, performance, python support, ruby
 support, clipboard support, and more.
 
 To run all healthchecks, use: >vim
-
+    :checkhealth
-        :checkhealth
 <
+
 Plugin authors are encouraged to write new healthchecks. |health-dev|
 
+
 COMMANDS                                                     *health-commands*
 
                                                            *:che* *:checkhealth*
@@ -56,7 +56,6 @@ Local mappings in the healthcheck buffer:
 q               Closes the window.
 
 Global configuration:
-
                                                                     *g:health*
 g:health  Dictionary with the following optional keys:
           - `style` (`'float'|nil`) Set to "float" to display :checkhealth in
@@ -65,16 +64,26 @@ g:health  Dictionary with the following optional keys:
           Example: >lua
             vim.g.health = { style = 'float' }
 
+
+Local configuration:
+
+Checkhealth sets its buffer filetype to "checkhealth". You can customize the
+buffer by handling the |FileType| event. For example if you don't want emojis
+in the health report: >vim
+    autocmd FileType checkhealth :set modifiable | silent! %s/\v( ?[^\x00-\x7F])//g
+<
+
+
 --------------------------------------------------------------------------------
 Create a healthcheck                                              *health-dev*
 
 Healthchecks are functions that check the user environment, configuration, or
 any other prerequisites that a plugin cares about. Nvim ships with
 healthchecks in:
-        - $VIMRUNTIME/autoload/health/
+• $VIMRUNTIME/autoload/health/
-        - $VIMRUNTIME/lua/vim/lsp/health.lua
+• $VIMRUNTIME/lua/vim/lsp/health.lua
-        - $VIMRUNTIME/lua/vim/treesitter/health.lua
+• $VIMRUNTIME/lua/vim/treesitter/health.lua
-        - and more...
+• and more...
 
 To add a new healthcheck for your own plugin, simply create a "health.lua"
 module on 'runtimepath' that returns a table with a "check()" function. Then
@@ -82,35 +91,35 @@ module on 'runtimepath' that returns a table with a "check()" function. Then
 
 For example if your plugin is named "foo", define your healthcheck module at
 one of these locations (on 'runtimepath'):
-        - lua/foo/health/init.lua
+• lua/foo/health/init.lua
-        - lua/foo/health.lua
+• lua/foo/health.lua
 
-If your plugin also provides a submodule named "bar" for which you want
+If your plugin also provides a submodule named "bar" for which you want a
-a separate healthcheck, define the healthcheck at one of these locations:
+separate healthcheck, define the healthcheck at one of these locations:
-        - lua/foo/bar/health/init.lua
+• lua/foo/bar/health/init.lua
-        - lua/foo/bar/health.lua
+• lua/foo/bar/health.lua
 
 All such health modules must return a Lua table containing a `check()`
 function.
 
 Copy this sample code into `lua/foo/health.lua`, replacing "foo" in the path
 with your plugin name: >lua
+    local M = {}
 
-        local M = {}
+    M.check = function()
+      vim.health.start("foo report")
+      -- make sure setup function parameters are ok
+      if check_setup() then
+        vim.health.ok("Setup is correct")
+      else
+        vim.health.error("Setup is incorrect")
+      end
+      -- do some more checking
+      -- ...
+    end
 
-        M.check = function()
+    return M
-          vim.health.start("foo report")
+<
-          -- make sure setup function parameters are ok
-          if check_setup() then
-            vim.health.ok("Setup is correct")
-          else
-            vim.health.error("Setup is incorrect")
-          end
-          -- do some more checking
-          -- ...
-        end
-
-        return M
 
 
 error({msg}, {...})                                       *vim.health.error()*

runtime/doc/news.txt

@@ -343,6 +343,8 @@ PLUGINS
   • 'commentstring' values can now be specified in a Treesitter capture's
     `bo.commentstring` metadata field, providing finer grained support for
     languages like `JSX`.
+• Customize :checkhealth by handling a `FileType checkhealth` event.
+  |health-usage|
 
 STARTUP
 

runtime/lua/vim/health.lua

@@ -1,16 +1,16 @@
 --- @brief
----<pre>help
---- vim.health is a minimal framework to help users troubleshoot configuration and
---- any other environment conditions that a plugin might care about. Nvim ships
---- with healthchecks for configuration, performance, python support, ruby
---- support, clipboard support, and more.
 ---
---- To run all healthchecks, use: >vim
+--- vim.health is a minimal framework to help users troubleshoot configuration and any other
+--- environment conditions that a plugin might care about. Nvim ships with healthchecks for
+--- configuration, performance, python support, ruby support, clipboard support, and more.
 ---
----         :checkhealth
+--- To run all healthchecks, use:
---- <
+--- ```vim
+--- :checkhealth
+--- ```
 --- Plugin authors are encouraged to write new healthchecks. |health-dev|
 ---
+---<pre>help
 --- COMMANDS                                *health-commands*
 ---
 ---                                                              *:che* *:checkhealth*
@@ -46,7 +46,6 @@
 --- q               Closes the window.
 ---
 --- Global configuration:
----
 ---                                                              *g:health*
 --- g:health  Dictionary with the following optional keys:
 ---           - `style` (`'float'|nil`) Set to "float" to display :checkhealth in
@@ -55,53 +54,64 @@
 ---           Example: >lua
 ---             vim.g.health = { style = 'float' }
 ---
+---</pre>
+---
+--- Local configuration:
+---
+--- Checkhealth sets its buffer filetype to "checkhealth". You can customize the buffer by handling
+--- the |FileType| event. For example if you don't want emojis in the health report:
+--- ```vim
+--- autocmd FileType checkhealth :set modifiable | silent! %s/\v( ?[^\x00-\x7F])//g
+--- ```
+---
+---<pre>help
 --- --------------------------------------------------------------------------------
 --- Create a healthcheck                                    *health-dev*
+---</pre>
 ---
---- Healthchecks are functions that check the user environment, configuration, or
+--- Healthchecks are functions that check the user environment, configuration, or any other
---- any other prerequisites that a plugin cares about. Nvim ships with
+--- prerequisites that a plugin cares about. Nvim ships with healthchecks in:
---- healthchecks in:
+--- - $VIMRUNTIME/autoload/health/
----         - $VIMRUNTIME/autoload/health/
+--- - $VIMRUNTIME/lua/vim/lsp/health.lua
----         - $VIMRUNTIME/lua/vim/lsp/health.lua
+--- - $VIMRUNTIME/lua/vim/treesitter/health.lua
----         - $VIMRUNTIME/lua/vim/treesitter/health.lua
+--- - and more...
----         - and more...
 ---
---- To add a new healthcheck for your own plugin, simply create a "health.lua"
+--- To add a new healthcheck for your own plugin, simply create a "health.lua" module on
---- module on 'runtimepath' that returns a table with a "check()" function. Then
+--- 'runtimepath' that returns a table with a "check()" function. Then |:checkhealth| will
---- |:checkhealth| will automatically find and invoke the function.
+--- automatically find and invoke the function.
 ---
 --- For example if your plugin is named "foo", define your healthcheck module at
 --- one of these locations (on 'runtimepath'):
----         - lua/foo/health/init.lua
+--- - lua/foo/health/init.lua
----         - lua/foo/health.lua
+--- - lua/foo/health.lua
 ---
---- If your plugin also provides a submodule named "bar" for which you want
+--- If your plugin also provides a submodule named "bar" for which you want a separate healthcheck,
---- a separate healthcheck, define the healthcheck at one of these locations:
+--- define the healthcheck at one of these locations:
----         - lua/foo/bar/health/init.lua
+--- - lua/foo/bar/health/init.lua
----         - lua/foo/bar/health.lua
+--- - lua/foo/bar/health.lua
 ---
---- All such health modules must return a Lua table containing a `check()`
+--- All such health modules must return a Lua table containing a `check()` function.
---- function.
 ---
---- Copy this sample code into `lua/foo/health.lua`, replacing "foo" in the path
+--- Copy this sample code into `lua/foo/health.lua`, replacing "foo" in the path with your plugin
---- with your plugin name: >lua
+--- name:
 ---
----         local M = {}
+--- ```lua
+--- local M = {}
 ---
----         M.check = function()
+--- M.check = function()
----           vim.health.start("foo report")
+---   vim.health.start("foo report")
----           -- make sure setup function parameters are ok
+---   -- make sure setup function parameters are ok
----           if check_setup() then
+---   if check_setup() then
----             vim.health.ok("Setup is correct")
+---     vim.health.ok("Setup is correct")
----           else
+---   else
----             vim.health.error("Setup is incorrect")
+---     vim.health.error("Setup is incorrect")
----           end
+---   end
----           -- do some more checking
+---   -- do some more checking
----           -- ...
+---   -- ...
----         end
+--- end
 ---
----         return M
+--- return M
----</pre>
+--- ```
 
 local M = {}
 
@@ -385,7 +395,6 @@ function M._check(mods, plugin_names)
     vim.cmd.bwipe('health://')
   end
   vim.cmd.file('health://')
-  vim.cmd.setfiletype('checkhealth')
 
   -- This should only happen when doing `:checkhealth vim`
   if next(healthchecks) == nil then
@@ -463,6 +472,7 @@ function M._check(mods, plugin_names)
 
   -- Once we're done writing checks, set nomodifiable.
   vim.bo[bufnr].modifiable = false
+  vim.cmd.setfiletype('checkhealth')
 end
 
 return M

test/functional/plugin/health_spec.lua

@@ -78,6 +78,15 @@ describe(':checkhealth', function()
     ]])
     )
   end)
+
+  it("vim.provider works with a misconfigured 'shell'", function()
+    clear()
+    command([[set shell=echo\ WRONG!!!]])
+    command('let g:loaded_perl_provider = 0')
+    command('let g:loaded_python3_provider = 0')
+    command('checkhealth vim.provider')
+    eq(nil, string.match(curbuf_contents(), 'WRONG!!!'))
+  end)
 end)
 
 describe('vim.health', function()
@@ -109,6 +118,33 @@ describe('vim.health', function()
       ]])
     end)
 
+    it('user FileType handler can modify report', function()
+      -- Define a FileType autocmd that removes emoji chars.
+      source [[
+        autocmd FileType checkhealth :set modifiable | silent! %s/\v( ?[^\x00-\x7F])//g
+        checkhealth full_render
+      ]]
+      n.expect([[
+
+      ==============================================================================
+      test_plug.full_render:                                              1  1
+
+      report 1 ~
+      - OK life is fine
+      - WARNING no what installed
+        - ADVICE:
+          - pip what
+          - make what
+
+      report 2 ~
+      - stuff is stable
+      - ERROR why no hardcopy
+        - ADVICE:
+          - :help |:hardcopy|
+          - :help |:TOhtml|
+      ]])
+    end)
+
     it('concatenates multiple reports', function()
       command('checkhealth success1 success2 test_plug')
       n.expect([[
@@ -245,17 +281,6 @@ describe('vim.health', function()
   end)
 end)
 
-describe(':checkhealth vim.provider', function()
-  it("works correctly with a wrongly configured 'shell'", function()
-    clear()
-    command([[set shell=echo\ WRONG!!!]])
-    command('let g:loaded_perl_provider = 0')
-    command('let g:loaded_python3_provider = 0')
-    command('checkhealth vim.provider')
-    eq(nil, string.match(curbuf_contents(), 'WRONG!!!'))
-  end)
-end)
-
 describe(':checkhealth window', function()
   before_each(function()
     clear { args = { '-u', 'NORC', '+set runtimepath+=test/functional/fixtures' } }