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Collections and proto builders which are created and mutated but never used may
be a sign of a bug, for example:
```java
MyProto.Builder builder = MyProto.newBuilder();
if (field != null) {
MyProto.NestedField.Builder nestedBuilder = MyProto.NestedField.newBuilder();
nestedBuilder.setValue(field);
// Oops--forgot to do anything with nestedBuilder.
}
return builder.build();
```
Likewise, converting a proto to a builder and modifying it is a no-op unless
something is done with the return value:
```java
void setFoo(MyProto proto, String foo) {
proto.toBuilder().setFoo(foo).build();
}
```
As protos are immutable, either the return value must be used:
```java
@CheckReturnValue
MyProto withFoo(MyProto proto, String foo) {
return proto.toBuilder().setFoo(foo).build();
}
```
or the Builder modified in place:
```java
void setFoo(MyProto.Builder protoBuilder, String foo) {
protoBuilder.setFoo(foo);
}
```
|
