Try hard to retain the unnamed register. Patch by Gernot Höflechner - LFDM.

doc/UltiSnips.txt

@@ -1397,6 +1397,7 @@ Contributors listed in chronological order:
    Romain Giot - rgiot
    Sergey Alexandrov - taketwo
    Brian Mock - saikobee
+   Gernot Höflechner - LFDM
 
 
 8.2 Snippets                                       *UltiSnips-contrisnippets*

plugin/UltiSnips.vim

@@ -227,6 +227,11 @@ endf
 function! UltiSnips_LeavingBuffer()
     exec g:_uspy "UltiSnips_Manager.leaving_buffer()"
 endf
+
+function! UltiSnips_LeavingInsertMode()
+    exec g:_uspy "UltiSnips_Manager.restore_unnamed_register()"
+endfunction
+
 " }}}
 " COMPLETE FUNCTIONS {{{
 function! UltiSnipsFiletypeComplete(arglead, cmdline, cursorpos)
@@ -262,6 +267,7 @@ exec g:_uspy "UltiSnips_Manager.backward_trigger = vim.eval('g:UltiSnipsJumpBack
 au CursorMovedI * call UltiSnips_CursorMoved()
 au CursorMoved * call UltiSnips_CursorMoved()
 au BufLeave * call UltiSnips_LeavingBuffer()
+au InsertLeave * call UltiSnips_LeavingInsertMode()
 
 call UltiSnips_MapKeys()
 

plugin/UltiSnips/__init__.py

@@ -553,8 +553,13 @@ class SnippetManager(object):
         self._supertab_keys = None
         self._csnippets = []
 
+        # needed to retain the unnamed register at all times
+        self._unnamed_reg_cached = False
+        self._last_placeholder = None
+
         self.reset()
 
+
     @err_to_scratch_buffer
     def reset(self, test_error=False):
         self._vstate = VimState()
@@ -832,10 +837,24 @@ class SnippetManager(object):
                 self._current_snippet_is_done()
                 jumped = self._jump(backwards)
         if jumped:
+            self._cache_unnamed_register()
             self._vstate.remember_position()
             self._ignore_movements = True
         return jumped
 
+    def _cache_unnamed_register(self):
+        self._unnamed_reg_cached = True
+        unnamed_reg = _vim.eval('@"')
+        if self._last_placeholder != unnamed_reg:
+          self._unnamed_reg_cache = unnamed_reg
+        self._last_placeholder = self._ctab._initial_text
+
+    def restore_unnamed_register(self):
+        if self._unnamed_reg_cached:
+            escaped_cache = self._unnamed_reg_cache.replace("'", "''")
+            _vim.command("let @\"='%s'" % escaped_cache)
+            self._unnamed_register_cached = False
+
     def _handle_failure(self, trigger):
         """
         Mainly make sure that we play well with SuperTab

test.py

@@ -3041,6 +3041,13 @@ class Bug1251994(_VimTest):
     wanted = "  world hello;blub"
 # End: 1251994  #}}}
 
+# Test for Github Pull Request #134 {{{#
+class RetainsTheUnnamedRegister(_VimTest):
+    snippets = ("test", "${1:hello} ${2:world} ${0}")
+    keys = "yank" + ESC + "by4lea test" + EX + "HELLO" + JF + JF + ESC + "p"
+    wanted = "yank HELLO world yank"
+# End: Github Pull Request # 134 #}}}
+
 class VerifyVimDict1(_VimTest):
     """check:
     correct type (4 means vim dictionary)