Anyone running into this recently, I found a work around.
I used "Entity has field" as a condition on the Computed Field Value.
I then used the "Add a variable" action to add a text value of the Computed Field as a variable.
Then added a "Convert Data Type" action to turn the value into an integer.
I could then use "Set a data value" as normal.
Here is an export of my rule (for a different use case), but still setting Computed Field values as a Variable...
{ "rules_set_default_remaining_balance" : {
"LABEL" : "Set Default Remaining Balance",
"PLUGIN" : "reaction rule",
"OWNER" : "rules",
"REQUIRES" : [ "rules", "entityform" ],
"ON" : { "entityform_insert" : [] },
"IF" : [
{ "entity_has_field" : { "entity" : [ "entityform" ], "field" : "field_total_price" } },
{ "entity_has_field" : { "entity" : [ "entityform" ], "field" : "field_remaining_balance" } },
{ "data_is_empty" : { "data" : [ "entityform:field-remaining-balance" ] } }
],
"DO" : [
{ "variable_add" : {
"USING" : { "type" : "text", "value" : [ "entityform:field-total-price" ] },
"PROVIDE" : { "variable_added" : { "variable_total_price" : "Total Price" } }
}
},
{ "data_convert" : {
"USING" : { "type" : "integer", "value" : [ "variable-total-price" ] },
"PROVIDE" : { "conversion_result" : { "conversion_result" : "Conversion result" } }
}
},
{ "data_set" : {
"data" : [ "entityform:field-remaining-balance" ],
"value" : [ "conversion-result" ]
}
}
]
}
}
In the example above, the field "Total Balance" is being Computed.