Allow updating subset of plugins

This commit extends `PlugInstall` and `PlugUpdate` command to allow
updating only a subset of plugins as follows:

    " With tab completion of plugin names
    :PlugInstall vim-easy-align seoul256
    :PlugUpdate vim-easy-align seoul256

README.md

@@ -60,14 +60,14 @@ before the call.
 
 ### Commands
 
-| Command                | Description                                                        |
-| ---------------------- | ------------------------------------------------------------------ |
-| PlugInstall [#threads] | Install plugins                                                    |
-| PlugUpdate  [#threads] | Install or update plugins                                          |
-| PlugClean[!]           | Remove unused directories (bang version will clean without prompt) |
-| PlugUpgrade            | Upgrade vim-plug itself                                            |
-| PlugStatus             | Check the status of plugins                                        |
-| PlugDiff               | See the updated changes from the previous PlugUpdate               |
+| Command                           | Description                                                        |
+| --------------------------------- | ------------------------------------------------------------------ |
+| PlugInstall [name ...] [#threads] | Install plugins                                                    |
+| PlugUpdate [name ...] [#threads]  | Install or update plugins                                          |
+| PlugClean[!]                      | Remove unused directories (bang version will clean without prompt) |
+| PlugUpgrade                       | Upgrade vim-plug itself                                            |
+| PlugStatus                        | Check the status of plugins                                        |
+| PlugDiff                          | See the updated changes from the previous PlugUpdate               |
 
 ### Options for parallel installer
 

plug.vim

@@ -24,7 +24,7 @@
 " You can change the location of the plugins with plug#begin(path) call.
 "
 "
-" Copyright (c) 2013 Junegunn Choi
+" Copyright (c) 2014 Junegunn Choi
 "
 " MIT License
 "
@@ -93,8 +93,8 @@ function! plug#begin(...)
   let g:plugs_order = []
 
   command! -nargs=+ -bar Plug   call s:add(1, <args>)
-  command! -nargs=* PlugInstall call s:install(<f-args>)
-  command! -nargs=* PlugUpdate  call s:update(<f-args>)
+  command! -nargs=* -complete=customlist,s:names PlugInstall call s:install(<f-args>)
+  command! -nargs=* -complete=customlist,s:names PlugUpdate  call s:update(<f-args>)
   command! -nargs=0 -bang PlugClean call s:clean('<bang>' == '!')
   command! -nargs=0 PlugUpgrade if s:upgrade() | execute "source ". s:me | endif
   command! -nargs=0 PlugStatus  call s:status()
@@ -372,19 +372,35 @@ function! s:finish(pull)
   endif
 endfunction
 
-function! s:update_impl(pull, args)
-  let threads = len(a:args) > 0 ? a:args[0] : get(g:, 'plug_threads', 16)
+function! s:names(...)
+  return filter(keys(g:plugs), 'stridx(v:val, a:1) == 0')
+endfunction
+
+function! s:update_impl(pull, args) abort
+  let args = copy(a:args)
+  let threads = (len(args) > 0 && args[-1] =~ '^[1-9][0-9]*$') ?
+                  \ remove(args, -1) : get(g:, 'plug_threads', 16)
+
+  let todo = empty(args) ? g:plugs :
+                \ filter(copy(g:plugs), 'index(args, v:key) >= 0')
+
+  if empty(todo)
+    echohl WarningMsg
+    echo 'No plugin to '. (a:pull ? 'update' : 'install') . '.'
+    echohl None
+    return
+  endif
 
   call s:prepare()
   call append(0, a:pull ? 'Updating plugins' : 'Installing plugins')
-  call append(1, '['. s:lpad('', len(g:plugs)) .']')
+  call append(1, '['. s:lpad('', len(todo)) .']')
   normal! 2G
   redraw
 
   if has('ruby') && threads > 1
-    call s:update_parallel(a:pull, threads)
+    call s:update_parallel(a:pull, todo, threads)
   else
-    call s:update_serial(a:pull)
+    call s:update_serial(a:pull, todo)
   endif
   call s:finish(a:pull)
 endfunction
@@ -413,10 +429,10 @@ function! s:update_progress(pull, cnt, bar, total)
   redraw
 endfunction
 
-function! s:update_serial(pull)
+function! s:update_serial(pull, todo)
   let st    = reltime()
   let base  = g:plug_home
-  let todo  = copy(g:plugs)
+  let todo  = copy(a:todo)
   let total = len(todo)
   let done  = {}
   let bar   = ''
@@ -468,7 +484,7 @@ function! s:update_serial(pull)
   call setline(1, "Updated. Elapsed time: " . split(reltimestr(reltime(st)))[0] . ' sec.')
 endfunction
 
-function! s:update_parallel(pull, threads)
+function! s:update_parallel(pull, todo, threads)
   ruby << EOF
   def esc arg
     %["#{arg.gsub('"', '\"')}"]
@@ -482,7 +498,7 @@ function! s:update_parallel(pull, threads)
   iswin = VIM::evaluate('s:is_win').to_i == 1
   pull  = VIM::evaluate('a:pull').to_i == 1
   base  = VIM::evaluate('g:plug_home')
-  all   = VIM::evaluate('copy(g:plugs)')
+  all   = VIM::evaluate('copy(a:todo)')
   limit = VIM::evaluate('get(g:, "plug_timeout", 60)')
   nthr  = VIM::evaluate('a:threads').to_i
   cd    = iswin ? 'cd /d' : 'cd'
@@ -494,7 +510,7 @@ function! s:update_parallel(pull, threads)
   take1 = proc { mtx.synchronize { running && all.shift } }
   logh  = proc {
     cnt = done.length
-    tot = VIM::evaluate('len(g:plugs)') || tot
+    tot = VIM::evaluate('len(a:todo)') || tot
     $curbuf[1] = "#{pull ? 'Updating' : 'Installing'} plugins (#{cnt}/#{tot})"
     $curbuf[2] = '[' + bar.ljust(tot) + ']'
     VIM::command('normal! 2G')

test/workflow.vader

@@ -296,6 +296,62 @@ Execute (Plug window in a new tab):
   q
   q
 
+**********************************************************************
+~ On-demand loading / Partial installation/update ~
+**********************************************************************
+
+Execute (Trying to execute on-demand commands when plugin is not installed):
+  call plug#begin()
+  Plug 'junegunn/vim-easy-align', { 'on': ['EasyAlign', 'LiveEasyAlign'] }
+  call plug#end()
+
+  Assert exists(':EasyAlign')
+  Assert exists(':LiveEasyAlign')
+  AssertThrows EasyAlign
+  AssertThrows LiveEasyAlign
+  Assert !exists(':EasyAlign')
+  Assert !exists(':LiveEasyAlign')
+
+Execute (New set of plugins):
+  call plug#begin()
+  Plug 'junegunn/vim-fnr' " Depends on vim-pseudocl
+  Plug 'junegunn/vim-easy-align', { 'on': 'EasyAlign' }
+  Plug 'junegunn/vim-redis',      { 'for': 'redis' }
+  call plug#end()
+
+Execute (Check commands):
+  Assert !exists(':FNR'),          'FNR command should not be found'
+  Assert !exists(':RedisExecute'), 'RedisExecute command should not be found'
+
+Execute (Partial PlugInstall):
+  PlugInstall vim-fnr vim-easy-align
+  PlugInstall vim-fnr vim-easy-align 1
+  q
+
+Given (Unaligned code):
+  a=1
+  aa=2
+
+Execute (Check installed plugins):
+  Assert exists(':FNR'),           'FNR command should be found'
+  Assert exists(':EasyAlign'),     'EasyAlign command should be found'
+  Assert !exists(':RedisExecute'), 'RedisExecute command still should not be found'
+  %EasyAlign=
+
+Expect (Aligned code):
+  a  = 1
+  aa = 2
+
+Given (nothing):
+Execute (Partial PlugUpdate):
+  PlugUpdate vim-redis
+  q
+
+Execute (On-demand loading based on filetypes):
+  Assert !exists(':RedisExecute'), 'RedisExecute command still should not be found'
+  set ft=redis
+  Assert exists(':RedisExecute'), 'RedisExecute command is now found'
+
 Execute (Cleanup):
   call system('rm -rf '.temp_plugged)