In this example, no Data Sources already exist (clean config).
If I enter the following into the CLI and hit <tab>:

/subsystem=datasources/data-source=:<tab>

I get no operation hints. If I use a bogus resource name that doesn't exist and hit <tab>:

[standalone@localhost:9999 /] /subsystem=datasources/data-source=DoesNotExistDS:<tab>

add disable enable flush-all-connection-in-pool
flush-idle-connection-in-pool read-attribute read-children-names read-children-resources
read-children-types read-operation-description read-operation-names read-resource
read-resource-description remove test-connection-in-pool validate-address
write-attribute

I get all the operations available. This should be made more consistent. The preference, IMO, would be to not have to specify a bogus name and still get the operations list:

[standalone@localhost:9999 /] /subsystem=datasources/data-source=:<tab>

or simpler yet:

[standalone@localhost:9999 /] /subsystem=datasources/data-source:<tab>

(no empty equal sign).