Reject non-string Info keys and values in info()

Info.info() accepted any key or value except None. A non-string such as
{'build_number': 42} was stored, and every later scrape of the registry
then failed with AttributeError ("'int' object has no attribute
'replace'"), so one bad call hid all metrics on the endpoint.

Check the types where the value is set, as was done for None in #1012,
so the caller gets a ValueError and the registry stays scrapeable. The
docs already say both keys and values must be strings.

Refs #1046

Signed-off-by: Sonica-B <shreyaa.boyane@gmail.com>

Author: Sonica-B

prometheus_client/metrics.py

@@ -749,6 +749,9 @@ def info(self, val: Dict[str, str]) -> None:
                 self._labelnames, val))
         if any(i is None for i in val.values()):
             raise ValueError('Label value cannot be None')
+        for k, v in val.items():
+            if not isinstance(k, str) or not isinstance(v, str):
+                raise ValueError(f'Info keys and values must be strings, got {k!r}: {v!r}')
         with self._lock:
             self._value = dict(val)
 

tests/test_core.py

@@ -17,6 +17,9 @@
 from prometheus_client.decorator import getargspec
 from prometheus_client.exposition import generate_latest
 from prometheus_client.metrics import _get_use_created
+from prometheus_client.openmetrics.exposition import (
+    generate_latest as openmetrics_generate_latest,
+)
 from prometheus_client.validation import (
     disable_legacy_validation, enable_legacy_validation,
 )
@@ -587,6 +590,17 @@ def test_labels(self):
         self.labels.labels('a').info({'foo': 'bar'})
         self.assertEqual(1, self.registry.get_sample_value('il_info', {'l': 'a', 'foo': 'bar'}))
 
+    def test_non_string_keys_and_values(self):
+        self.info.info({'version': '1.2.3'})
+        for val in ({'version': 1}, {'temperature': 49.0}, {1: 'x'}, {'tags': ['a', 'b']}):
+            with self.subTest(val=val):
+                self.assertRaises(ValueError, self.info.info, val)
+                self.assertRaises(ValueError, self.labels.labels('a').info, val)
+        # The rejected calls keep the previous value and the registry stays scrapeable.
+        self.assertEqual(1, self.registry.get_sample_value('i_info', {'version': '1.2.3'}))
+        self.assertIn(b'i_info{version="1.2.3"} 1.0', generate_latest(self.registry))
+        self.assertIn(b'i_info{version="1.2.3"} 1.0', openmetrics_generate_latest(self.registry))
+
 
 class TestEnum(unittest.TestCase):
     def setUp(self):