fix(grouping): Stop parameterizing message variable in custom titles

src/sentry/grouping/fingerprinting/utils.py

@@ -220,6 +220,7 @@ def resolve_fingerprint_variable(
     variable_key: str,
     event: Event,
     use_legacy_unknown_variable_handling: bool,
+    parameterize_message: bool = True,
 ) -> str | None:
     if variable_key == "transaction":
         return event.data.get("transaction") or "<no-transaction>"
@@ -230,6 +231,11 @@ def resolve_fingerprint_variable(
             or get_path(event.data, "logentry", "message")
             or get_path(event.data, "exception", "values", -1, "value")
         )
+
+        # Fingerprint variables can be used in custom titles, and there we want the original message
+        if not parameterize_message:
+            return message or "<no-message>"
+
         normalized_message = (
             normalize_message_for_grouping(message, event, source="fingerprint", trim_message=False)
             if message
@@ -332,7 +338,12 @@ def _handle_match(match: re.Match[str]) -> str:
         # can remove `use_legacy_unknown_variable_handling` and just return the value given by
         # `resolve_fingerprint_variable`
         resolved_value = resolve_fingerprint_variable(
-            variable_key, event, use_legacy_unknown_variable_handling
+            variable_key,
+            event,
+            use_legacy_unknown_variable_handling,
+            # Parameterization is useful for grouping, but we want to show the real error message in
+            # the event/issue title
+            parameterize_message=False,
         )
 
         # TODO: Once we have fully transitioned off of the `newstyle:2023-01-11` grouping config, we

tests/sentry/grouping/snapshots/test_fingerprinting/test_event_hash_variant/fingerprint_title_no_message_parameterization.pysnap

@@ -16,7 +16,7 @@ config:
 fingerprint:
 - dogs are great
 - '{{ message }}'
-title: 'Number <int> dog, dog #<int>'
+title: 'Number 1 dog, dog #1'
 variants:
   custom_server_fingerprint:
     contributes: true