rostopic publish constant value

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ROS messages allow the definition of constants (e.g. for emulating enum types). Is there a way to publish these named values in "rostopic pub"?

For example, I have a defined message type Emotion.msg:

uint32 emotion
float64 intensity
uint32 NEUTRAL=0
uint32 HAPPY=1
uint32 SAD=2

The idea is that the emotion value is set to one of the constants, and I don't really want to remember what the constants are as values.

The following works as expected, but is not ideal:

rostopic pub  --once /set_emotion my_msgs/Emotion  1 0.5

Rather, I want to publish something like

rostopic pub  --once /set_emotion my_msgs/Emotion  HAPPY 0.5

or at least

rostopic pub  --once /set_emotion my_msgs/Emotion my_msgs/Emotion/HAPPY 0.5

Neither of these seem to work, since the constants get interpreted as strings. Is there a way to specify named constants in the rostopic utility? Neither of these seems to work.