[draft] Add formatting support

autoload/lsc/format.vim

@@ -0,0 +1,83 @@
+" https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#textDocument_formatting
+" for the whole document
+" and
+" https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#textDocument_rangeFormatting
+" for ranges
+"
+"
+"
+
+function! s:FormattingOptions()
+  " TODO Not sure what things like clangd do with this stuff when they read
+  " their own configuration files, but it's a non-optional field in the
+  " formatting request params. Work out what it does, and make it configurable
+  " to users (probably per language, but maybe also globally; or both)
+  return {
+      \ 'tabSize': 8,
+      \ 'insertSpaces': v:false,
+      \ 'trimTrailingWhitespace': v:true,
+      \ 'insertFinalNewline': v:true,
+      \ 'trimFinalNewlines': v:true,
+      \}
+endfunction
+
+function! s:ApplyEdit(textedit)
+  " FIXME This is a hack. We probably don't want to use hack around workspace
+  " edits here
+  let l:workspace_edit = {'changes': {lsc#uri#documentUri(): a:textedit}}
+  return lsc#edit#apply(l:workspace_edit)
+endfunction
+
+function! s:OnResult(textedit) abort
+  "Response:
+
+  "  result: TextEdit[] | null describing the modification to the document to be formatted.
+  "  error: code and message set in case an exception happens during the range formatting request.
+  "
+  "  Since version 3.18.0
+
+ "call lsc#message#error('onresult')
+  if a:textedit == v:null | return | endif
+  call lsc#message#log('got edits' . json_encode(a:textedit), 'Info')
+  return s:ApplyEdit(a:textedit)
+endfunction
+
+function! s:OnSkip(bufnr, textedit) abort
+  call lsc#message#error('formatting skipped for ')
+endfunction
+
+function! s:startDocFormattingRequest() abort
+  let l:params = lsc#params#textDocument()
+  let l:params['options'] = s:FormattingOptions()
+  let l:server = lsc#server#forFileType(&filetype)[0]
+  call lsc#message#log('sending message' . json_encode(l:params), 'Info')
+  call l:server.request('textDocument/formatting', l:params,
+      \ lsc#util#gateResult('FormatDoc',
+      \     function('<SID>OnResult', []),
+      \     function('<SID>OnSkip', [bufnr('%')])))
+endfunction
+
+function! s:startRangeFormattingRequest(range) abort
+  let l:params = lsc#params#textDocument()
+  let l:params['range'] = a:range
+  let l:params['options'] = s:FormattingOptions()
+  let l:server = lsc#server#forFileType(&filetype)[0]
+  call l:server.request('textDocument/rangeFormatting', l:params,
+      \ lsc#util#gateResult('FormatRange',
+      \     function('<SID>OnResult', []),
+      \     function('<SID>OnSkip', [bufnr('%')])))
+endfunction
+
+function! lsc#format#formatFile() abort
+  return s:startDocFormattingRequest()
+endfunction
+
+function! lsc#format#formatRange() range abort
+  let l:range = {
+      \   'start': {'line': a:firstline - 1, 'character': 0},
+      \   'end': {'line': a:lastline - 1, 'character': strlen(getline("."))}
+      \}
+  call lsc#message#log('formatting range' . json_encode(l:range), 'Info')
+
+  return s:startRangeFormattingRequest(l:range)
+endfunction

plugin/lsc.vim

@@ -44,6 +44,8 @@ command! LSClientDisable call lsc#server#disable()
 command! LSClientEnable call lsc#server#enable()
 command! LSClientDisableDiagnosticHighlights call <SID>DisableHighlights()
 command! LSClientEnableDiagnosticHighlights call <SID>EnableHighlights()
+command! LSClientFormat call lsc#format#formatFile()
+command! -range LSClientFormat '<,'> call lsc#format#formatRange()
 
 if !exists('g:lsc_enable_apply_edit') || g:lsc_enable_apply_edit
   command! -nargs=? LSClientRename call lsc#edit#rename(<args>)