Having the data's schema be optional at the level of the 'Schema' did not allow to represent cases where there would be an opaque data at an arbitrary nesting. So I introduced a new variant 'Opaque' on 'Data' to fill that gap.
This has been removed from the CIP-0057 specification since validators
are often re-used for multiple purposes (especially validators with
arity 2). It's misleading to assign a validator a purpose since the
purpose distinction actually happens _within_ the validator itself.
Tracing is now turn OFF by default when:
- building project
- building documentation
- building dependencies
It can be turned ON only when building project using `--keep-traces`.
That means it's not possible to build dependencies with traces. The
address `--rebuild` flag will also rebuild without traces.
Tracing is however turn ON by default when:
- checking the project (and running tests).
In this scenario, tracing can be disabled using `--no-traces` (if for
example, one want to analyze the execution units of specific functions
without having to manually remove traces from code).
This caused me some trouble. In my first approach, I ended up having
multiple traces because nested values would be evaluated twice; once
as condition, and once as part of the continuation.
To prevent this, we can simply evaluate the condition once, and return
plain True / False boolean as outcome. So this effectively transforms any
expression:
```
expr
```
as
```
if expr { True } else { trace("...", False) }
```
We want the lookup to yield a result when there's only a single
validator; and no title is provided. So that users can simply do
'aiken address' in their project if it's unambiguous. The validator's
name is only required to disambiguate between multiple validators.
I also noticed that the order of arguments in with_validator was
wrong. Somehow.
This is still a bit clunky as the interface is expecting parameters in UPLC form and we don't do any kind of verification. So it is easy to shoot oneself in the foot at the moment (for example, to apply an integer into something that should have received a data). To be improved later.
