Use JSON formatting for all values except strings (#2644)

Author: ocelotl

exporter/opentelemetry-exporter-prometheus/src/opentelemetry/exporter/prometheus/__init__.py

@@ -211,6 +211,6 @@ def _sanitize(self, key: str) -> str:
     # pylint: disable=no-self-use
     def _check_value(self, value: Union[int, float, str, Sequence]) -> str:
         """Check the label value and return is appropriate representation"""
-        if not isinstance(value, str) and isinstance(value, Sequence):
+        if not isinstance(value, str):
             return dumps(value, default=str)
         return str(value)

exporter/opentelemetry-exporter-prometheus/tests/test_prometheus_exporter.py

@@ -205,3 +205,6 @@ def test_check_value(self):
         self.assertEqual(collector._check_value([1, 2]), "[1, 2]")
         self.assertEqual(collector._check_value((1, 2)), "[1, 2]")
         self.assertEqual(collector._check_value(["a", 2]), '["a", 2]')
+        self.assertEqual(collector._check_value(True), "true")
+        self.assertEqual(collector._check_value(False), "false")
+        self.assertEqual(collector._check_value(None), "null")