How can I provide a default value if a field is ONLY null?

[bitwizeshift]

This seems like a basic question, but I can't seem to find a working solution. A search through the existing Q&A didn't yield the same question, so please excuse me if it's been asked before.

I have a document that looks like:

some-node:
  enabled: false

I want to select the .some-node.enabled and, if it's not specified (i.e. null) it will default to true.

The problem is that the expression .some-node.enabled // true yields true 100% of the time because, for some reason, // coalesces to false or null to the second value. What I'm wanting is something that does true coalescing of only null values.

Some sources are suggesting instead using an if statement, but any time I attempt something like:

.some-node | if has("enabled") then .enabled else true end

It fails with an error like:

$ yq '.some-node | if has("enabled") then .enabled else true end' document.yaml
Error: 1:14: invalid input text "if has(\"enabled\"..."

I'm sure I'm overlooking something simple; this must be supported, right?