Issue with OPA repl on iterating

[psibi]

Expected Behavior

> test = [true,true]
Rule 'test' defined in package repl. Type 'show' to see rules.
> test[_]
+ True
+ True

Actual Behavior

> test = [true,true]
Rule 'test' defined in package repl. Type 'show' to see rules.
> test[_]
+
+

Steps to Reproduce the Problem

~ $ opa run
OPA 0.19.0-dev (commit 0aff6264-dirty, built at 2020-03-29T14:04:08Z)

Run 'help' to see a list of commands.

> test = [true,true]
Rule 'test' defined in package repl. Type 'show' to see rules.
> test[_]
+
+

Additional Info

@tsandall added some additional info in Slack:

Yeah looks like a bug in the way output is pretty printed. If you turn off pretty printing, e.g., enter json in the REPL to switch to json mode, you'll see the answer is correct.

[tsandall]

For expected behaviour here I'd want to see the same thing we get if you substitute true for any other value except false:

> x[_]
+------+
| x[_] |
+------+
| 1    |
| 1    |
+------+

[tsandall]

If anyone wants to work on this, feel free to ping me and I can provide some pointers.