Fixes Bug #427676.

- Adds the idea of anonymous snippets with new method on SnippetManager to expand a snippet without adding it.
- Adds two new functions for adding new snippets, and expanding anonymous snippets.
- Adds tests for the above functionality.

plugin/UltiSnips.vim

@@ -135,6 +135,32 @@ function! UltiSnips_JumpForwards()
  return ""
 endfunction
 
+function! UltiSnips_AddSnippet(trigger, value, descr, options, ...)
+ " Takes the same arguments as SnippetManager.add_snippet:
+ " (trigger, value, descr, options, ft = "all", globals = None)
+py << EOB
+args = vim.eval("a:000")
+trigger = vim.eval("a:trigger")
+value = vim.eval("a:value")
+descr = vim.eval("a:descr")
+options = vim.eval("a:options")
+
+UltiSnips_Manager.add_snippet(trigger, value, descr, options, *args)
+EOB
+ return ""
+endfunction
+
+function! UltiSnips_Anon(value, ...)
+ " Takes the same arguments as SnippetManager.expand_anon:
+ " (value, trigger="", descr="", options="", globals = None)
+py << EOB
+args = vim.eval("a:000")
+value = vim.eval("a:value")
+UltiSnips_Manager.expand_anon(value, *args)
+EOB
+ return ""
+endfunction
+
 function! UltiSnips_MapKeys()
    " Map the keys correctly
    if g:UltiSnipsExpandTrigger == g:UltiSnipsJumpForwardTrigger

plugin/UltiSnips/__init__.py

@@ -656,6 +656,16 @@ class SnippetManager(object):
             Snippet(trigger, value, descr, options, globals or {})
         )
 
+    def expand_anon(self, value, trigger="", descr="", options="", globals=None):
+        if globals is None:
+            globals = {}
+
+        before, after = self._get_before_after()
+        snip = Snippet(trigger, value, descr, options, globals)
+
+        if snip.matches(before):
+            self._do_snippet(snip, before, after)
+
     def clear_snippets(self, triggers = [], ft = "all"):
         if ft in self._snippets:
             self._snippets[ft].clear_snippets(triggers)
@@ -907,7 +917,10 @@ class SnippetManager(object):
         """
         lineno,col = vim.current.window.cursor
         # Adjust before, maybe the trigger is not the complete word
-        text_before = before[:-len(snippet.matched)]
+
+        text_before = before
+        if snippet.matched:
+            text_before = before[:-len(snippet.matched)]
 
         self._expect_move_wo_change = True
         if self._cs:

test.py

@@ -43,6 +43,7 @@ JF = "?" # Jump forwards
 JB = "+" # Jump backwards
 LS = "@" # List snippets
 EX = "\t" # EXPAND
+EA = "#" # Expand anonymous
 
 # Some VIM functions
 COMPL_KW = chr(24)+chr(14)
@@ -1718,6 +1719,67 @@ class ListAllAvailable_NonDefined_NoExceptionShouldBeRaised(_ListAllSnippets):
     keys = "hallo qualle" + LS + "Hi"
     wanted = "hallo qualleHi"
 
+
+#######################
+# ANONYMOUS EXPANSION #
+#######################
+
+class _AnonBase(_VimTest):
+    args = ""
+    def _options_on(self):
+        self.send(":inoremap <silent> " + EA + ' <C-R>=UltiSnips_Anon('
+                + self.args + ')<cr>\n')
+    def _options_off(self):
+        self.send(":iunmap <silent> " + EA + ' <C-R>=UltiSnips_Anon('
+                + self.args + ')<cr>\n')
+
+class Anon_NoTrigger_Simple(_AnonBase):
+    args = '"simple expand"'
+    keys = "abc" + EA
+    wanted = "abcsimple expand"
+
+class Anon_NoTrigger_Multi(_AnonBase):
+    args = '"simple $1 expand $1 $0"'
+    keys = "abc" + EA + "123" + JF + "456"
+    wanted = "abcsimple 123 expand 123 456"
+
+class Anon_Trigger_Multi(_AnonBase):
+    args = '"simple $1 expand $1 $0", "abc"'
+    keys = "123 abc" + EA + "123" + JF + "456"
+    wanted = "123 simple 123 expand 123 456"
+
+class Anon_Trigger_Simple(_AnonBase):
+    args = '"simple expand", "abc"'
+    keys = "abc" + EA
+    wanted = "simple expand"
+
+class Anon_Trigger_Opts(_AnonBase):
+    args = '"simple expand", ".*abc", "desc", "r"'
+    keys = "blah blah abc" + EA
+    wanted = "simple expand"
+
+
+########################
+# ADD SNIPPET FUNCTION #
+########################
+
+class _AddFuncBase(_VimTest):
+    args = ""
+    def _options_on(self):
+        self.send(":call UltiSnips_AddSnippet("
+                + self.args + ')\n')
+
+class AddFunc_Simple(_AddFuncBase):
+    args = '"test", "simple expand", "desc", ""'
+    keys = "abc test" + EX
+    wanted = "abc simple expand"
+
+class AddFunc_Opt(_AddFuncBase):
+    args = '".*test", "simple expand", "desc", "r"'
+    keys = "abc test" + EX
+    wanted = "simple expand"
+
+
 #########################
 # SNIPPETS FILE PARSING #
 #########################