Rework condition caching to support nested evaluation

[ehuelsmann]

Description

Prior to this change, only top-level condition outcomes were cached;
however, use of conditions isn't restricted to the top level, yet
with caching one would expect exactly a single condition evaluation
per block of cached conditions.

Note: this change is created for the purpose of discussion and therefor marked as Draft.

Type of change

I'm not sure if this is a bug fix or a new feature: we were supposed to have a condition cache, but nested condition evaluations weren't cached at all... (Which, given the lack of issues registered about this situation since its creation -- some 17 years ago -- might be an over-engineered function?)

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project, please see the contribution guidelines.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[todo]

We may just want to pass the error up

https://github.com/jonasbn/perl-workflow/blob/f0d893a28964a61e3e22c23eaf6fca0d31976118/lib/Workflow/Condition.pm#L107-L112

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This comment was generated by todo based on a TODO comment in f0d893a in #90. cc @ehuelsmann.

[todo]

**** We need a deprecation warning of some sort! This is

https://github.com/jonasbn/perl-workflow/blob/f0d893a28964a61e3e22c23eaf6fca0d31976118/lib/Workflow/Condition.pm#L363-L368

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This comment was generated by todo based on a TODO comment in f0d893a in #90. cc @ehuelsmann.

[coveralls]

Coverage decreased (-0.3%) to 81.955% when pulling f692b76 on ehuelsmann:cache-nested-conditions into f604055 on jonasbn:master.

[ehuelsmann]

discussed this topic on Slack with @oliwel last Friday. Although he didn't intimately review the change, he did get and endorsed the structure and direction of the change.

[ehuelsmann]

@jonasbn, based on your review feedback, I'll resolve the two "TODO" items that the bot complained about. That is, assuming you'll accept the basic idea behind this change.

[jonasbn]

Hi @ehuelsmann

Sorry about the radio silence, life/work is busy at the moment. I have skimmed the PR and I can see that this review will require some time, so I am just writing to let you know that I am on it

[jonasbn]

I am all for improvements in caching, the implementation looks promising, but is is extensive and I am not sure if I complete get all the details.

I do find the term "opposite" confusing when reading the code.

Please evaluate my comments, they are as always by no means dictation

[jonasbn]

Looks good