Rework epp subtype detection

The previous work had some problems:

* it was working for nvim but not at all for vim.
* it did not provide any loop-breaking checks before launching doautocmd
* it was setting `filetype` from within the syntax file instead of the
  ftdetect file.

This reworks the code to fix most of the above issues. The changes are
almost verbatim what Time Pope wrote for the eruby syntax and ftplugin
files in vim/nvim.

With the changes, vim now is able to correctly identify the subtype
based on the file name's extension prior to .epp. This covers most of the
basic cases.

However, I was not able to find a good way to solve finding the filetype
based on parsing file contents and the paths leading to the file. We
don't want to reimplement the whole of builtin file detection, which is
why @shadowwa was trying to reuse the autocommands already determined.

Until we find a way to fix the above issue, we at least now have most of
the filetype detection working, which is better than nothing.

NOTE: I'm intentionally keeping the tests that are failing for vim in
this commit. This way ppl who will investigate this project in the
future will be able to see that the tests actually pass on nvim, but not
on vim.
The next commit will comment out the failing tests though, since
vader.vim still doesn't have a SkipIf instruction.
See: junegunn/vader.vim#201

ftdetect/puppet.lua

@@ -8,7 +8,7 @@ vim.filetype.add({
                 path_wo_epp = path:sub(1,-5)
                 matched = vim.filetype.match({ buf = bufnr, filename = path_wo_epp })
                 if matched ~= nil and matched ~= 'mason' then
-                    vim.b.original_filetype = matched
+                    vim.b.epuppet_subtype = matched
                 end
                 return 'epuppet'
             end,

ftdetect/puppet.vim

@@ -1,24 +1,23 @@
 " vint: -ProhibitAutocmdWithNoGroup
-" Vim's own filetypes.vim runs before all ftdetect scripts (why?) and matches
-" detects the .pp extension as being a 'pascal' file. Since the script uses
-" `setf`, we can nullify the filetype detection by removing all commands bound
-" to BufRead and BufNewFile for .pp files with `au!`. Hopefully, if there were
-" any other commands set they were associated with the pascal type and we want
-" to get rid of them.
-" However, this has the effect of completely nullifying pascal type detection
-" for .pp files.
-au! BufRead,BufNewFile *.pp setfiletype puppet
-" Some epp files may get marked as "mason" type before this script is reached.
-" Vim's own scripts.vim forces the type if it detects a `<%` at the start of
-" the file. All files ending in .epp should be epuppet
-if !has('nvim-0.8.0')
-    autocmd! BufRead,BufNewFile *.epp call DetectOriginalType()
-    function! DetectOriginalType()
-        execute 'doautocmd filetypedetect BufRead ' .fnameescape(expand('<afile>:r'))
-        if &filetype !=# '' && !( &filetype ==# 'mason' && expand('<afile>') !~# 'mason')
-            let b:original_filetype = &filetype
-        endif
-        setlocal filetype=epuppet
-    endfunction
+" Vim has fixed puppet vs pascal detection in patch 8.2.2334 so we can rely on
+" their type detection from that point on.
+if !has("patch-8.2.2334") && !has("nvim-0.5.0")
+  " Vim's own filetypes.vim runs before all ftdetect scripts (why?) and matches
+  " detects the .pp extension as being a 'pascal' file. Since the script uses
+  " `setf`, we can nullify the filetype detection by removing all commands bound
+  " to BufRead and BufNewFile for .pp files with `au!`. Hopefully, if there were
+  " any other commands set they were associated with the pascal type and we want
+  " to get rid of them.
+  " However, this has the effect of completely nullifying pascal type detection
+  " for .pp files.
+  au! BufRead,BufNewFile *.pp setfiletype puppet
+endif
+" Vim now has autodetection for epuppet and Puppetfile. We only need to add
+" autocommands for older versions of vim / neovim
+if !has("patch-8.2.2402") && !has("nvim-0.5.0")
+  " Some epp files may get marked as "mason" type before this script is reached.
+  " Vim's own scripts.vim forces the type if it detects a `<%` at the start of
+  " the file. All files ending in .epp should be epuppet
+  au! BufRead,BufNewFile *.epp setf epuppet
+  au BufRead,BufNewFile Puppetfile setfiletype ruby
 endif
-au BufRead,BufNewFile Puppetfile setfiletype ruby

ftplugin/epuppet.vim

@@ -14,9 +14,48 @@ set cpo-=C
 
 " Define some defaults in case the included ftplugins don't set them.
 let s:undo_ftplugin = ''
-let s:browsefilter = "All Files (*.*)\t*.*\n"
+if has("win32")
+  let s:browsefilter = "All Files (*.*)\t*.*\n"
+else
+    let s:browsefilter = "All Files (*)\t*\n"
+endif
 let s:match_words = ''
 
+if !exists("g:epuppet_default_subtype")
+  let g:epuppet_default_subtype = "sh"
+endif
+
+if &filetype =~ '^epuppet\.'
+    let b:epuppet_subtype = matchstr(&filetype,'^epuppet\.\zs\w\+')
+elseif !exists('b:epuppet_subtype')
+  let b:epuppet_subtype = matchstr(substitute(expand("%:t"),'\c\%(\.epp\)\+$','',''),'\.\zs\w\+\%(\ze+\w\+\)\=$')
+  " TODO instead of listing exceptions like this, can we instead recognize
+  "  extension -> type mapping?
+  if b:epuppet_subtype == 'rhtml'
+    let b:epuppet_subtype = 'html'
+  elseif b:epuppet_subtype == 'rb'
+    let b:epuppet_subtype = 'ruby'
+  elseif b:epuppet_subtype == 'yml'
+    let b:epuppet_subtype = 'yaml'
+  elseif b:epuppet_subtype == 'js'
+    let b:epuppet_subtype = 'javascript'
+  elseif b:epuppet_subtype == 'txt'
+    " Conventional; not a real file type
+    let b:epuppet_subtype = 'text'
+  elseif b:epuppet_subtype == 'py'
+    let b:epuppet_subtype = 'python'
+  elseif b:epuppet_subtype == 'rs'
+    let b:epuppet_subtype = 'rust'
+  elseif b:epuppet_subtype == ''
+    let b:epuppet_subtype = g:epuppet_default_subtype
+  endif
+endif
+
+if exists("b:epuppet_subtype") && b:epuppet_subtype != '' && b:epuppet_subtype !=? 'epuppet'
+  exe "runtime! ftplugin/".b:epuppet_subtype.".vim ftplugin/".b:epuppet_subtype."_*.vim ftplugin/".b:epuppet_subtype."/*.vim"
+endif
+unlet! b:did_ftplugin
+
 runtime! ftplugin/sh.vim
 unlet! b:did_ftplugin
 

syntax/epuppet.vim

@@ -9,14 +9,40 @@ if exists('b:current_syntax')
   finish
 endif
 
-if exists('b:original_filetype')
-    runtime! syntax/'.b:original_filetype .'.vim'
-    " allow original filetype detection by other plugins like ale or coc.nvim
-    let &filetype=b:original_filetype .'.epuppet'
-else
-    runtime! syntax/sh.vim
+if !exists("g:epuppet_default_subtype")
+  let g:epuppet_default_subtype = "sh"
+endif
+
+if &filetype =~ '^epuppet\.'
+  let b:epuppet_subtype = matchstr(&filetype,'^epuppet\.\zs\w\+')
+elseif !exists('b:epuppet_subtype')
+  let b:epuppet_subtype = matchstr(substitute(expand("%:t"),'\c\%(\.epp\)\+$','',''),'\.\zs\w\+\%(\ze+\w\+\)\=$')
+  " TODO instead of listing exceptions like this, can we instead recognize
+  "  extension -> type mapping?
+  if b:epuppet_subtype == 'rhtml'
+    let b:epuppet_subtype = 'html'
+  elseif b:epuppet_subtype == 'rb'
+    let b:epuppet_subtype = 'ruby'
+  elseif b:epuppet_subtype == 'yml'
+    let b:epuppet_subtype = 'yaml'
+  elseif b:epuppet_subtype == 'js'
+    let b:epuppet_subtype = 'javascript'
+  elseif b:epuppet_subtype == 'txt'
+    " Conventional; not a real file type
+    let b:epuppet_subtype = 'text'
+  elseif b:epuppet_subtype == 'py'
+    let b:epuppet_subtype = 'python'
+  elseif b:epuppet_subtype == 'rs'
+    let b:epuppet_subtype = 'rust'
+  elseif b:epuppet_subtype == ''
+    let b:epuppet_subtype = g:epuppet_default_subtype
+  endif
+endif
+
+if exists("b:epuppet_subtype") && b:epuppet_subtype != '' && b:epuppet_subtype !=? 'epuppet'
+  exe "runtime! syntax/".b:epuppet_subtype.".vim"
+  unlet! b:current_syntax
 endif
-unlet! b:current_syntax
 
 syn include @puppetTop syntax/puppet.vim
 
@@ -31,9 +57,4 @@ syn region  ePuppetComment    matchgroup=ePuppetDelimiter start="<%-\=#"    end=
 hi def link ePuppetDelimiter              PreProc
 hi def link ePuppetComment                Comment
 
-if exists('b:original_filetype')
-    let b:current_syntax = b:original_filetype . '.epuppet'
-else
-    let b:current_syntax = 'epuppet'
-endif
-
+let b:current_syntax = 'epuppet'

test/filetype/epuppet.vader

@@ -8,20 +8,26 @@ Execute (epuppet test_with_leading_tag):
 
 Execute (epuppet perl with shebang):
   edit test/test-files/test_perl_with_shebang.epp
-  AssertEqual &filetype, 'perl.epuppet'
+  AssertEqual &filetype, 'epuppet'
+  AssertEqual b:epuppet_subtype, 'perl'
 
-Execute (epuppet shell with shebang):
+# We don't need to parse the shebang for shell since sh is the default subtype
+Execute (epuppet default to shell):
   edit test/test-files/test_shell_with_shebang.epp
-  AssertEqual &filetype, 'sh.epuppet'
+  AssertEqual &filetype, 'epuppet'
+  AssertEqual b:epuppet_subtype, 'sh'
 
 Execute (epuppet shell with extension):
   edit test/test-files/test_shell_with_extension.sh.epp
-  AssertEqual &filetype, 'sh.epuppet'
+  AssertEqual &filetype, 'epuppet'
+  AssertEqual b:epuppet_subtype, 'sh'
 
 Execute (epuppet php with extension):
   edit test/test-files/test_php_with_extension.php.epp
-  AssertEqual &filetype, 'php.epuppet'
+  AssertEqual &filetype, 'epuppet'
+  AssertEqual b:epuppet_subtype, 'php'
 
 Execute (epuppet apache conf with path and extension):
   edit test/test-files/etc/apache2/test.conf.epp
-  AssertEqual &filetype, 'apache.epuppet'
+  AssertEqual &filetype, 'epuppet'
+  AssertEqual b:epuppet_subtype, 'apache'