Ensure Result.messages is always unique

2 files changed, 12 insertions, 1 deletions

diff --git a/mammoth/lists.py b/mammoth/lists.py
index cf39b99..6e39ae0 100644
--- a/mammoth/lists.py
+++ b/mammoth/lists.py
@@ -14,6 +14,15 @@ def _collect(values, result):
         elif value is not None:
             result.append(value)
 
+def unique(values):
+    output = []
+    seen = set()
+    for value in values:
+        if value not in seen:
+            seen.add(value)
+            output.append(value)
+    return output
+
 
 if sys.version_info[0] == 2:
     map = map
diff --git a/mammoth/results.py b/mammoth/results.py
index 9112296..59c3a42 100644
--- a/mammoth/results.py
+++ b/mammoth/results.py
@@ -1,10 +1,12 @@
 import collections
 
+from .lists import unique
+
 
 class Result(object):
     def __init__(self, value, messages):
         self.value = value
-        self.messages = messages
+        self.messages = unique(messages)
     
     def map(self, func):
         return Result(func(self.value), self.messages)