Automatically detect indentation, closes #529

plugin/sleuth.vim

@@ -0,0 +1,164 @@
+" Heuristically set buffer options
+"
+" Modified version of vim-sleuth:
+"   - softtab and tabstop reduced from 8 to 2
+"   - number of considered lines reduced from 1024 to 64
+"   - maximum 6 other files are checked instead of 20
+"   - check maximum of files 2 per directory level instead of 8
+"   - maximum of 3 directory levels are checked
+"   - globs are concatenated for performance
+
+if exists("g:loaded_sleuth") || v:version < 700 || &cp
+  finish
+endif
+let g:loaded_sleuth = 1
+
+function! s:guess(lines) abort
+  let options = {}
+  let heuristics = {'spaces': 0, 'hard': 0, 'soft': 0}
+  let ccomment = 0
+  let podcomment = 0
+  let triplequote = 0
+  let backtick = 0
+  let xmlcomment = 0
+  let softtab = repeat(' ', 2)
+
+  for line in a:lines
+    if !len(line) || line =~# '^\s*$'
+      continue
+    endif
+
+    if line =~# '^\s*/\*'
+      let ccomment = 1
+    endif
+    if ccomment
+      if line =~# '\*/'
+        let ccomment = 0
+      endif
+      continue
+    endif
+
+    if line =~# '^=\w'
+      let podcomment = 1
+    endif
+    if podcomment
+      if line =~# '^=\%(end\|cut\)\>'
+        let podcomment = 0
+      endif
+      continue
+    endif
+
+    if triplequote
+      if line =~# '^[^"]*"""[^"]*$'
+        let triplequote = 0
+      endif
+      continue
+    elseif line =~# '^[^"]*"""[^"]*$'
+      let triplequote = 1
+    endif
+
+    if backtick
+      if line =~# '^[^`]*`[^`]*$'
+        let backtick = 0
+      endif
+      continue
+    elseif &filetype ==# 'go' && line =~# '^[^`]*`[^`]*$'
+      let backtick = 1
+    endif
+
+    if line =~# '^\s*<\!--'
+      let xmlcomment = 1
+    endif
+    if xmlcomment
+      if line =~# '-->'
+        let xmlcomment = 0
+      endif
+      continue
+    endif
+
+    if line =~# '^\t'
+      let heuristics.hard += 1
+    elseif line =~# '^' . softtab
+      let heuristics.soft += 1
+    endif
+    if line =~# '^  '
+      let heuristics.spaces += 1
+    endif
+    let indent = len(matchstr(substitute(line, '\t', softtab, 'g'), '^ *'))
+    if indent > 1 && (indent < 4 || indent % 2 == 0) &&
+          \ get(options, 'shiftwidth', 99) > indent
+      let options.shiftwidth = indent
+    endif
+  endfor
+
+  if heuristics.hard && !heuristics.spaces
+    return {'expandtab': 0, 'shiftwidth': &tabstop}
+  elseif heuristics.soft != heuristics.hard
+    let options.expandtab = heuristics.soft > heuristics.hard
+    if heuristics.hard
+      let options.tabstop = 2
+    endif
+  endif
+
+  return options
+endfunction
+
+function! s:apply_if_ready(options) abort
+  if !has_key(a:options, 'expandtab') || !has_key(a:options, 'shiftwidth')
+    return 0
+  else
+    for [option, value] in items(a:options)
+      call setbufvar('', '&'.option, value)
+    endfor
+    return 1
+  endif
+endfunction
+
+function! s:detect() abort
+  if &buftype ==# 'help'
+    return
+  endif
+
+  let options = s:guess(getline(1, 64))
+  if s:apply_if_ready(options)
+    return
+  endif
+  let c = 6
+  let pattern = c > 0 ? sleuth#GlobForFiletype(&filetype) : ''
+  let dir = expand('%:p:h')
+  let level = 3
+  while isdirectory(dir) && dir !=# fnamemodify(dir, ':h') && c > 0 && level > 0
+    let level -= 1
+    for neighbor in glob(dir.'/'.pattern,0,1)[0:1]
+      if neighbor !=# expand('%:p') && filereadable(neighbor)
+        call extend(options, s:guess(readfile(neighbor, '', 32)), 'keep')
+        let c -= 1
+      endif
+      if s:apply_if_ready(options)
+        let b:sleuth_culprit = neighbor
+        return
+      endif
+      if c <= 0
+        break
+      endif
+    endfor
+    if c <= 0
+      break
+    endif
+    let dir = fnamemodify(dir, ':h')
+  endwhile
+  if has_key(options, 'shiftwidth')
+    return s:apply_if_ready(extend({'expandtab': 1}, options))
+  endif
+endfunction
+
+setglobal smarttab
+
+if !exists('g:did_indent_on')
+  filetype indent on
+endif
+
+augroup polyglot
+  autocmd!
+  autocmd FileType * call s:detect()
+augroup END