fix for correct error reporting

pythonx/UltiSnips/snippet/source/file/_base.py

@@ -69,8 +69,12 @@ class SnippetFileSource(SnippetSource):
         if ft in self._snippets:
             del self._snippets[ft]
             del self._extends[ft]
-        for fn in self._files_for_ft[ft]:
-            self._parse_snippets(ft, fn)
+        try:
+            for fn in self._files_for_ft[ft]:
+                self._parse_snippets(ft, fn)
+        except:
+            del self._files_for_ft[ft]
+            raise
         # Now load for the parents
         for parent_ft in self.get_deep_extends([ft]):
             if parent_ft != ft and self._needs_update(parent_ft):

test/test_ContextSnippets.py

@@ -101,3 +101,15 @@ class ContextSnippets_PriorityKeyword(_VimTest):
 
     keys = "i" + EX
     wanted = "b"
+
+
+class ContextSnippets_ReportError(_VimTest):
+    files = { 'us/all.snippets': r"""
+        snippet e "desc" "Tru" e
+        error
+        endsnippet
+        """}
+
+    keys = "e" + EX
+    wanted = "e" + EX
+    expected_error = r"NameError: name 'Tru' is not defined"