No empty object

aip/cloud/25001.md

@@ -0,0 +1,66 @@
+---
+id: 25001
+state: draft
+created: TBD
+placement:
+  category: gcp
+---
+
+# Empty Objects
+
+Fields of type Message **must not** be empty. Empty messages do not have uniform
+
+## Alternatives
+
+The presence of empty Messages are sometimes used to indicate that a flag is enabled. Alternatives to empty Messages could include a single boolean field within the Message to signify enablement or an Enum rather than an empty Message.
+
+### Add Field to Message
+For example:
+```proto
+message EnableMyFeature {
+}
+```
+Could be modeled instead as:
+
+```proto
+message MyFeature {
+  bool enabled = 1;
+}
+```
+
+### Move Option to Top-Level Enum
+
+For a situation where the presence of an empty Message indicates a certain option is being chosen, an alternative is to choose the option via an enum rather than the presence of a particular object.
+
+For example:
+```proto
+oneof access_model {
+  AccessModelFree free = 1
+  AccessModelQuota quota = 2
+}
+
+message AccessModelFree {
+}
+
+message AccessModelQuota {
+  int32 requests_per_day = 1;
+}
+```
+
+Could be modeled instead as:
+```proto
+enum AccessModel {
+  UNSPECIFIED = 0;
+  FREE = 1;
+  QUOTA = 1;
+}
+
+message AccessModelQuota {
+  int32 requests_per_day = 1;
+}
+```
+
+
+## Changelog
+
+- **TBD**: Created