Add style guide note that if you prefix enum values, that the names with the prefix stripped should be legal and style-conformant names.

PiperOrigin-RevId: 839806167

Author: protobuf-github-bot

content/programming-guides/style.md

@@ -187,6 +187,28 @@ some languages don't support an enum being defined inside a "struct" type,
 preferring prefixed values ensures a consistent approach across binding
 languages.
 
+When prefixing enum values, the remainder of the name with the prefix stripped
+should still be a legal and style-conformant enum name. For example, avoid the
+following:
+
+```
+enum DeviceTier {
+  DEVICE_TIER_UNKNOWN = 0;
+  DEVICE_TIER_1 = 1;
+  DEVICE_TIER_2 = 2;
+}
+```
+
+Instead, use a value name like `DEVICE_TIER_TIER1`, where the `DEVICE_TIER_`
+portion is viewed as scoping the enum value rather than as part of the
+individual enum value name. Some Protobuf implementations automatically strip
+the prefix that matches the containing enum name where it is safe to do so, but
+could not in this example since a bare `1` is not a legal enum value name.
+
+A future Edition will add support for scoped enums, which will eliminate the
+need to manually prefix each enum value and enable this to be written succinctly
+as `TIER1 = 1`.
+
 ## Services {#services}
 
 Use TitleCase for service names and method names.