New 'session_persist_globals' option (requested by Roman Byshko)

README.md

@@ -30,7 +30,7 @@ This command saves your current editing session just like Vim's built-in [:mkses
 
 If the session you're trying to save is already active in another Vim instance you'll get a warning and nothing happens. You can use a bang (!) as in `:SaveSession! ...` to ignore the warning and save the session anyway.
 
-As mentioned earlier your session script will be saved in the directory pointed to by `g:session_directory`.
+Your session script will be saved in the directory pointed to by the `g:session_directory` option.
 
 ### The `:OpenSession` command
 
@@ -74,14 +74,22 @@ Execute this command to view the Vim script generated for a session. This comman
 
 ### The `sessionoptions` setting
 
-Because the `session.vim` plug-in uses Vim's [:mksession][mksession] command you can change how it works by setting ['sessionoptions'](http://vimdoc.sourceforge.net/htmldoc/options.html#%27sessionoptions%27) in your [vimrc script] [vimrc], for example:
+Because the `session.vim` plug-in uses Vim's [:mksession][mksession] command you can change how it works by setting ['sessionoptions'][sessionoptions] in your [vimrc script] [vimrc], for example:
 
     " If you only want to save the current tab page:
     set sessionoptions-=tabpages
 
     " If you don't want help windows to be restored:
     set sessionoptions-=help
 
+Note that the session.vim plug-in automatically and unconditionally executes the following changes just before saving a session:
+
+    " Don't persist options and mappings because it can corrupt sessions.
+    set sessionoptions-=options
+
+    " Always persist Vim's window size.
+    set sessionoptions+=resize
+
 ### The `g:session_directory` option
 
 This option controls the location of your session scripts. Its default value is `~/.vim/sessions` (on UNIX) or `~\vimfiles\sessions` (on Windows). If you don't mind the default you don't have to do anything; the directory will be created for you. Note that a leading `~` is expanded to your current home directory (`$HOME` on UNIX, `%USERPROFILE%` on Windows).
@@ -98,6 +106,15 @@ By default this option is set to `'prompt'`. When you've opened a session and yo
 
 By default this option is set to false (0). When you set this option to true (1) and you start Vim, the session plug-in will open your last used session instead of the default session. Note that the session plug-in will still show you the dialog asking whether you want to restore the last used session. To get rid of the dialog you have to set `g:session_autoload` to `'yes'`.
 
+### The `g:session_persist_globals` option
+
+The session.vim plug-in uses Vim's [:mksession] [mksession] command but it changes ['sessionoptions'][sessionoptions] so that Vim options and mappings are not persisted. The plug-in does this because persistence of options and mappings can break loading of sessions, in other words it's fragile (in my opinion).
+
+If you want the plug-in to persist specific global variables or options you can add their names to the list `g:session_persist_globals` in your [vimrc script] [vimrc]:
+
+    " Persist the value of the global option 'makeprg'.
+    call add(g:session_persist_globals, '&makeprg')
+
 ### The `g:session_restart_environment` option
 
 This option is a list of environment variable names (without the dollar signs) that the `:RestartVim` command will pass on to the new instance of Vim. This option is only useful on UNIX. By default the three environment variables `$TERM`, `$VIM` and `$VIMRUNTIME` are included in this list.
@@ -231,3 +248,4 @@ Here's an example session script generated by the `session.vim` plug-in while I
 [mksession]: http://vimdoc.sourceforge.net/htmldoc/starting.html#:mksession
 [source]: http://vimdoc.sourceforge.net/htmldoc/repeat.html#:source
 [vimrc]: http://vimdoc.sourceforge.net/htmldoc/starting.html#vimrc
+[sessionoptions]: http://vimdoc.sourceforge.net/htmldoc/options.html#%27sessionoptions%27

autoload/xolox/session.vim

@@ -1,9 +1,9 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: October 1, 2011
+" Last Change: November 11, 2011
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '1.4.20'
+let g:xolox#session#version = '1.4.21'
 
 " Public API for session persistence. {{{1
 
@@ -20,6 +20,7 @@ function! xolox#session#save_session(commands, filename) " {{{2
   call add(a:commands, '')
   call add(a:commands, 'set guioptions=' . escape(&go, ' "\'))
   call add(a:commands, 'silent! set guifont=' . escape(&gfn, ' "\'))
+  call xolox#session#save_globals(a:commands)
   call xolox#session#save_features(a:commands)
   call xolox#session#save_colors(a:commands)
   call xolox#session#save_qflist(a:commands)
@@ -29,6 +30,12 @@ function! xolox#session#save_session(commands, filename) " {{{2
   call add(a:commands, '" vim: ft=vim ro nowrap smc=128')
 endfunction
 
+function! xolox#session#save_globals(commands) " {{{2
+  for global in g:session_persist_globals
+    call add(a:commands, printf("let %s = %s", global, string(eval(global))))
+  endfor
+endfunction
+
 function! xolox#session#save_features(commands) " {{{2
   let template = "if exists('%s') != %i | %s %s | endif"
   for [global, command] in [

doc/session.txt

@@ -64,8 +64,8 @@ If the session you're trying to save is already active in another Vim instance
 you'll get a warning and nothing happens. You can use a bang (!) as in
 ':SaveSession! ...' to ignore the warning and save the session anyway.
 
-As mentioned earlier your session script will be saved in the directory
-pointed to by |g:session_directory|.
+Your session script will be saved in the directory pointed to by the
+|g:session_directory| option.
 
 -------------------------------------------------------------------------------
 The *:OpenSession* command
@@ -151,6 +151,15 @@ how it works by setting |'sessionoptions'| in your |vimrc| script, for example:
     " If you don't want help windows to be restored:
     set sessionoptions-=help
 
+Note that the session.vim plug-in automatically and unconditionally executes
+the following changes just before saving a session:
+>
+    " Don't persist options and mappings because it can corrupt sessions.
+    set sessionoptions-=options
+    
+    " Always persist Vim's window size.
+    set sessionoptions+=resize
+
 -------------------------------------------------------------------------------
 The *g:session_directory* option
 
@@ -188,6 +197,21 @@ instead of the default session. Note that the session plug-in will still show
 you the dialog asking whether you want to restore the last used session. To
 get rid of the dialog you have to set |g:session_autoload| to 'yes'.
 
+-------------------------------------------------------------------------------
+The *g:session_persist_globals* option
+
+The session.vim plug-in uses Vim's |:mksession| command but it changes
+|'sessionoptions'| so that Vim options and mappings are not persisted. The
+plug-in does this because persistence of options and mappings can break
+loading of sessions, in other words it's fragile (in my opinion).
+
+If you want the plug-in to persist specific global variables or options you
+can add their names to the list |g:session_persist_globals| in your |vimrc|
+script:
+>
+    " Persist the value of the global option 'makeprg'.
+    call add(g:session_persist_globals, '&makeprg')
+
 -------------------------------------------------------------------------------
 The *g:session_restart_environment* option
 

plugin/session.vim

@@ -1,6 +1,6 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: October 1, 2011
+" Last Change: November 11, 2011
 " URL: http://peterodding.com/code/vim/session/
 
 " Support for automatic update using the GLVS plug-in.
@@ -34,6 +34,11 @@ if !exists('g:session_default_to_last')
   let g:session_default_to_last = 0
 endif
 
+" List with global variables and &options to persist between sessions.
+if !exists('g:session_persist_globals')
+  let g:session_persist_globals = []
+endif
+
 " On UNIX the :RestartVim command will pass the following environment
 " variables on to the new instance of Vim.
 if !exists('g:session_restart_environment')