De-duplicate entries in placeholders

Will save some env var lookups when input contains multiple
instances of same variable. Also cleaner if we later want to do
something with that list of variables.

Change-Id: If37b75abe7366dcf49426da34c10675d8ebab132

1 files changed, 1 insertions, 1 deletions

diff --git a/yaml-to-json.py b/yaml-to-json.py
index bd3e0ac..4da2eae 100755
--- a/yaml-to-json.py
+++ b/yaml-to-json.py
@@ -16,7 +16,7 @@ def main():
 
     placeholders = map(lambda match: match.group('named', 'braced'),
                        string.Template.pattern.finditer(template.template))
-    placeholders = filter(None, itertools.chain(*placeholders))
+    placeholders = set(filter(None, itertools.chain(*placeholders)))
 
     # Pretend that missing environment variables are set to empty strings.
     # It would be better to throw an error on missing environment variables,