Re: [PATCH proxmox 01/29] add new proxmox-match-expression crate

["Lukas Wagner" <l.wagner@proxmox.com>]

On Fri Sep 4, 2026 at 2:25 PM CEST, Robert Obkircher wrote:
>
> On 04.09.26 11:48, Lukas Wagner wrote:
>>>> [..]
>>>> +    pub fn evaluate(&self, data: &D) -> Result<EvaluatedExpressionWithResult<M>, E> {
>>>> +        let evaluated_expression = match self {
>>>> +            Expression::AllOf(expressions) => {
>>>> +                if expressions.is_empty() {
>>>> +                    // 'all-of' without any sub-expressions is *not* a match
>>>> +                    EvaluatedExpressionWithResult {
>>>> +                        expression: EvaluatedExpression::AllOf(Vec::new()),
>>>> +                        matches: false,
>>>> +                    }
>>> this probaly does not matter too much as long as it's documented, but
>>> intuitively (and based on implementations for all-expressions in 
>>> other languages like rust and python) i would expect all([]) to evaluate to
>>> true.
>> Yeah, I see where you are coming from, but after some consideration I've
>> decided that I'd like to keep it this way.
>>
>> For non-coders, all([]) being true is not very intuitive, and I'd prefer
>> to just say "hey, all combinators eval to false if they have no
>> children" in the docs.
>
> Even non-coders understand why all of my Ferraris are red :)
>
> Would it be possible to forbid the empty lists entirely? e.g. by
> rewriting all([]) to true when someone saves an empty list.
>

I'm not sure if I'm a fan of automatically rewriting rules, I think this
is counter-intuitive for users.

But, giving this another thought:

  - since proxmox-match-expression is supposed to be generic, keep it 'mathmatically' correct,
    so let all([]) eval to true
  - disallow creating empty all-of/any-of/one-of rules in the UI and API

What do you think?