Add option to disable session locking (issue #112)

Please refer to issue #112 on GitHub:
  #112

README.md

@@ -135,6 +135,13 @@ The vim-session plug-in uses lock files to prevent double loading of sessions. T
 2. If the directory `/var/lock` exists and is writable that is used as a sane default.
 3. As a sane fall back for platforms where `/var/lock` is not available the directory that stores the session scripts themselves is used.
 
+### The `g:session_lock_enabled` option
+
+Depending on your workflow locking of editing sessions can get annoying at times, so if you don't care about opening a session more than once and potentially "losing a version of your session" then you can use this option to completely disable session locking as follows:
+
+    " Disable all session locking - I know what I'm doing :-).
+    let g:session_lock_enabled = 0
+
 ### The `g:session_default_name` option
 
 The name of the default session without directory or filename extension (you'll never guess what the default is).
@@ -263,8 +270,8 @@ Recently this plug-in switched from reimplementing [:mksession][mksession] to ac
 
 <!-- Start of generated documentation -->
 
-The documentation of the 37 functions below was extracted from
-2 Vim scripts on February 13, 2015 at 13:25.
+The documentation of the 38 functions below was extracted from
+2 Vim scripts on February 18, 2015 at 22:56.
 
 ### Public API for the vim-session plug-in
 
@@ -471,6 +478,14 @@ scoped session. Saves a copy of the original value to be restored later.
 
 Restore the original value of Vim's [sessionoptions] [] option.
 
+#### The `xolox#session#locking_enabled()` function
+
+Check whether session locking is enabled. Returns true (1) when locking is
+enabled, false (0) otherwise.
+
+By default session locking is enabled but users can opt-out by setting
+`g:session_lock_enabled` to false (0).
+
 ### Example function for session name suggestions
 
 #### The `xolox#session#suggestions#vcs_feature_branch()` function

autoload/xolox/session.vim

@@ -1,10 +1,10 @@
 " Public API for the vim-session plug-in.
 "
 " Author: Peter Odding
-" Last Change: February 13, 2015
+" Last Change: February 18, 2015
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '2.8'
+let g:xolox#session#version = '2.9'
 
 " Public API for session persistence. {{{1
 
@@ -499,15 +499,17 @@ function! xolox#session#auto_unlock() " {{{2
   " [VimLeavePre] [] automatic command event.
   "
   " [VimLeavePre]: http://vimdoc.sourceforge.net/htmldoc/autocmd.html#VimLeavePre
-  let i = 0
-  while i < len(s:lock_files)
-    let lock_file = s:lock_files[i]
-    if delete(lock_file) == 0
-      call remove(s:lock_files, i)
-    else
-      let i += 1
-    endif
-  endwhile
+  if xolox#session#locking_enabled()
+    let i = 0
+    while i < len(s:lock_files)
+      let lock_file = s:lock_files[i]
+      if delete(lock_file) == 0
+        call remove(s:lock_files, i)
+      else
+        let i += 1
+      endif
+    endwhile
+  endif
 endfunction
 
 " Commands that enable users to manage multiple sessions. {{{1
@@ -1007,6 +1009,15 @@ if !exists('s:lock_files')
   let s:lock_files = []
 endif
 
+function! xolox#session#locking_enabled()
+  " Check whether session locking is enabled. Returns true (1) when locking is
+  " enabled, false (0) otherwise.
+  "
+  " By default session locking is enabled but users can opt-out by setting
+  " `g:session_lock_enabled` to false (0).
+  return xolox#misc#option#get('session_lock_enabled', 1)
+endfunction
+
 function! s:vim_instance_id()
   let id = {'pid': getpid()}
   if !empty(v:servername)
@@ -1045,6 +1056,9 @@ function! s:lock_file_path(session_path)
 endfunction
 
 function! s:lock_session(session_path)
+  if !xolox#session#locking_enabled()
+    return 1
+  endif
   let lock_file = s:lock_file_path(a:session_path)
   if xolox#misc#persist#save(lock_file, s:vim_instance_id())
     if index(s:lock_files, lock_file) == -1
@@ -1055,6 +1069,9 @@ function! s:lock_session(session_path)
 endfunction
 
 function! s:unlock_session(session_path)
+  if !xolox#session#locking_enabled()
+    return 1
+  endif
   let lock_file = s:lock_file_path(a:session_path)
   if delete(lock_file) == 0
     let idx = index(s:lock_files, lock_file)
@@ -1066,6 +1083,9 @@ function! s:unlock_session(session_path)
 endfunction
 
 function! s:session_is_locked(session_name, command)
+  if !xolox#session#locking_enabled()
+    return 0
+  endif
   let session_path = xolox#session#name_to_path(a:session_name)
   let lock_file = s:lock_file_path(session_path)
   if filereadable(lock_file)

doc/session.txt

@@ -21,21 +21,22 @@ Contents ~
   1. The |sessionoptions| setting
   2. The |g:session_directory| option
   3. The |g:session_lock_directory| option
-  4. The |g:session_default_name| option
-  5. The |g:session_default_overwrite| option
-  6. The |g:session_extension| option
-  7. The |g:session_autoload| option
-  8. The |g:session_autosave| option
-  9. The |g:session_autosave_periodic| option
-  10. The |g:session_verbose_messages| option
-  11. The |g:session_default_to_last| option
-  12. The |g:session_persist_colors| option
-  13. The |g:session_persist_globals| option
-  14. The |g:session_restart_environment| option
-  15. The |g:session_command_aliases| option
-  16. The |g:session_menu| option
-  17. The |g:session_name_suggestion_function| option
-  18. The |g:loaded_session| option
+  4. The |g:session_lock_enabled| option
+  5. The |g:session_default_name| option
+  6. The |g:session_default_overwrite| option
+  7. The |g:session_extension| option
+  8. The |g:session_autoload| option
+  9. The |g:session_autosave| option
+  10. The |g:session_autosave_periodic| option
+  11. The |g:session_verbose_messages| option
+  12. The |g:session_default_to_last| option
+  13. The |g:session_persist_colors| option
+  14. The |g:session_persist_globals| option
+  15. The |g:session_restart_environment| option
+  16. The |g:session_command_aliases| option
+  17. The |g:session_menu| option
+  18. The |g:session_name_suggestion_function| option
+  19. The |g:loaded_session| option
  5. Compatibility with other plug-ins |session-compatibility-with-other-plug-ins|
  6. Known issues                                         |session-known-issues|
  7. Function reference                             |session-function-reference|
@@ -65,6 +66,7 @@ Contents ~
    23. The |xolox#session#include_tabs()| function
    24. The |xolox#session#change_tab_options()| function
    25. The |xolox#session#restore_tab_options()| function
+   26. The |xolox#session#locking_enabled()| function
   2. Example function for session name suggestions |example-function-for-session-name-suggestions|
    1. The |xolox#session#suggestions#vcs_feature_branch()| function
  8. Contact                                                   |session-contact|
@@ -322,6 +324,17 @@ factors:
 3. As a sane fall back for platforms where '/var/lock' is not available the
    directory that stores the session scripts themselves is used.
 
+-------------------------------------------------------------------------------
+The *g:session_lock_enabled* option
+
+Depending on your workflow locking of editing sessions can get annoying at
+times, so if you don't care about opening a session more than once and
+potentially "losing a version of your session" then you can use this option to
+completely disable session locking as follows:
+>
+  " Disable all session locking - I know what I'm doing :-).
+  let g:session_lock_enabled = 0
+<
 -------------------------------------------------------------------------------
 The *g:session_default_name* option
 
@@ -529,8 +542,8 @@ might take a while...)
                                                    *session-function-reference*
 Function reference ~
 
-The documentation of the 37 functions below was extracted from 2 Vim scripts on
-February 13, 2015 at 13:25.
+The documentation of the 38 functions below was extracted from 2 Vim scripts on
+February 18, 2015 at 22:56.
 
 -------------------------------------------------------------------------------
                                            *public-api-for-vim-session-plug-in*
@@ -743,6 +756,15 @@ The *xolox#session#restore_tab_options()* function
 Restore the original value of Vim's sessionoptions (see |'sessionoptions'|)
 option.
 
+-------------------------------------------------------------------------------
+The *xolox#session#locking_enabled()* function
+
+Check whether session locking is enabled. Returns true (1) when locking is
+enabled, false (0) otherwise.
+
+By default session locking is enabled but users can opt-out by setting
+|g:session_lock_enabled| to false (0).
+
 -------------------------------------------------------------------------------
                                 *example-function-for-session-name-suggestions*
 Example function for session name suggestions ~