Added support for snippet option "w" for word-boundary triggers.

doc/UltiSnips.txt

@@ -180,9 +180,15 @@ snippet on. The options currently supported are >
        of the cursor). Default is to expand snippets at every position, even
        mitten in the line. Most of my snippets have this option set, it keeps
        UltiSnips out of the way. 
-   i   Inword expansion - normally, triggers need whitespace before them to be
+   i   Inword expansion - Normally, triggers need whitespace before them to be
        expanded. With this option, triggers are also expanded in the middle of
        a word.
+   w   Word boundary - Normally, triggers need whitespace before them to be
+       expanded. With this option, the trigger will be expanded at a "word"
+       boundary as well, where word characters are letters, digits, and the
+       underscore character ('_').  This enables expansion of a trigger that
+       adjoins punctuation (for example) without expanding suffixes of larger
+       words.
 
 4.2 Plaintext snippets                         *UltiSnips-plaintext-snippets*
 ----------------------

plugin/UltiSnips/__init__.py

@@ -96,14 +96,42 @@ class Snippet(object):
         return "Snippet(%s,%s,%s)" % (self._t,self._d,self._opts)
 
     def matches(self, trigger):
-        if "i" not in self._opts:
+        # If user supplies both "w" and "i", it should perhaps be an
-            return trigger == self._t
+        # error, but if permitted it seems that "w" should take precedence
-        return trigger.endswith(self._t)
+        # (since matching at word boundary and within a word == matching at word
+        # boundary).
+        if "w" in self._opts:
+            trigger_len = len(self._t)
+            trigger_prefix = trigger[:-trigger_len]
+            trigger_suffix = trigger[-trigger_len:]
+            match = (trigger_suffix == self._t)
+            if match and trigger_prefix:
+                # Require a word boundary between prefix and suffix.
+                boundaryChars = trigger_prefix[-1:] + trigger_suffix[:1]
+                match = re.match(r'.\b.', boundaryChars)
+        elif "i" in self._opts:
+            match = trigger.endswith(self._t)
+        else:
+            match = (trigger == self._t)
+        return match
 
     def could_match(self, trigger):
-        # it i hard to define when a inword snippet could match
+        if "w" in self._opts:
-        # therefore we do not specially look for it
+            # Trim non-empty prefix up to word boundary, if present.
-        return self._t.startswith(trigger)
+            trigger_suffix = re.sub(r'^.+\b(.+)$', r'\1', trigger)
+            match = self._t.startswith(trigger_suffix)
+
+            # TODO: list_snippets() function cannot handle partial-trigger
+            # matches yet, so for now fail if we trimmed the prefix.
+            if trigger_suffix != trigger:
+                match = False
+        elif "i" in self._opts:
+            # TODO: It is hard to define when a inword snippet could match,
+            # therefore we check only for full-word trigger.
+            match = self._t.startswith(trigger)
+        else:
+            match = self._t.startswith(trigger)
+        return match
 
     def overwrites_previous(self):
         return "!" in self._opts

test.py

@@ -1099,6 +1099,28 @@ class SnippetOptions_ExpandInwordSnippetsWithOtherChars_Expand3(_VimTest):
     keys = "ätest" + EX
     wanted = "äExpand me!"
 
+class _SnippetOptions_ExpandWordSnippets(_VimTest):
+    snippets = (("test", "Expand me!", "", "w"), )
+class SnippetOptions_ExpandWordSnippets_NormalExpand(
+        _SnippetOptions_ExpandWordSnippets):
+    keys = "test" + EX
+    wanted = "Expand me!"
+class SnippetOptions_ExpandWordSnippets_NoExpand(
+    _SnippetOptions_ExpandWordSnippets):
+    keys = "atest" + EX
+    wanted = "atest"
+class SnippetOptions_ExpandWordSnippets_ExpandSuffix(
+    _SnippetOptions_ExpandWordSnippets):
+    keys = "a-test" + EX
+    wanted = "a-Expand me!"
+class SnippetOptions_ExpandWordSnippets_ExpandSuffix2(
+    _SnippetOptions_ExpandWordSnippets):
+    keys = "a(test" + EX
+    wanted = "a(Expand me!"
+class SnippetOptions_ExpandWordSnippets_ExpandSuffix3(
+    _SnippetOptions_ExpandWordSnippets):
+    keys = "[[test" + EX
+    wanted = "[[Expand me!"
 
 
 ######################