openmetrics: Throw error on blank line (#576)

As per current spec draft blank lines are not allowed

Signed-off-by: Manuel Rüger <[email protected]>

Author: mrueg

prometheus_client/openmetrics/parser.py

@@ -482,6 +482,9 @@ def build_metric(name, documentation, typ, unit, samples):
         if eof:
             raise ValueError("Received line after # EOF: " + line)
 
+        if not line:
+            raise ValueError("Received blank line")
+
         if line == '# EOF':
             eof = True
         elif line.startswith('#'):

tests/openmetrics/test_parser.py

@@ -598,6 +598,8 @@ def test_invalid_input(self):
         for case in [
             # No EOF.
             (''),
+            # Blank line
+            ('a 1\n\n# EOF\n'),
             # Text after EOF.
             ('a 1\n# EOF\nblah'),
             ('a 1\n# EOFblah'),