[RUST] Add Eq and Hash Trait to Rust client struct to allow Hashset usage

[Snazzie]

Resolves #20412
Hashset insert requires Eq and Hash traits.. This change will allow inserting generated struct into Hashsets.

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[Snazzie]

@frol @farcaller @richardwhiuk @paladinzh @jacob-pro

[wing328]

@Snazzie thanks for the PR

can you please review the CI failures when you've time?

[Snazzie]

Hmm, my rust and mustache knowledge is a bit low. Im not sure the best way to support for number types (i16, f32 etc) with Eq and Hash.
would need support from someone more experienced.

it looks like i have to do separate implements like so. where need conditional hash implementation on all properties.

@wing328

impl Eq for PizzaSpeziale {}

if type is f64

impl Hash for PizzaSpeziale {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.pizza_size.map(|v| v.to_bits()).hash(state);
    }
}

if type is i32

impl Hash for PizzaSpeziale {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.pizza_size.map(|v| v.to_be()).hash(state);
    }
}

perhapse in mustache something like this

impl Eq for {{{classname}}} {}
impl Hash for {{{classname}}} {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        // Combine hashes of all fields
        {{#vars}}
            {{#isInteger}}
                self.{{name}}.map(|v| v.to_bits()).hash(state);
        {{/vars}}
    }
}

or keep existing trait and use wrappers for number types.

struct F64Wrapper(f64);

[wing328]

Im not sure the best way to support for number types (i16, f32 etc) with Eq and Hash.

what about using isLong and isShort in the template?

e.g.

openapi-generator/modules/openapi-generator/src/main/resources/Java/libraries/jersey3/oneof_model.mustache

Lines 96 to 101 in 3d65786

	{{#isLong}}
	attemptParsing |= (token == JsonToken.VALUE_NUMBER_INT);
	{{/isLong}}
	{{#isShort}}
	attemptParsing |= (token == JsonToken.VALUE_NUMBER_INT);
	{{/isShort}}

[devhl-labs]

Am i alone in thinking that eq and hash should not be implemented by default? Im assuming your including all properties in the hash calculation, but what if the entity has an id property? I would expect only the id to be considered in the hash. Since we cant tell which properties are the id imho we should not implement hash or equals.

[Snazzie]

Am i alone in thinking that eq and hash should not be implemented by default? Im assuming your including all properties in the hash calculation, but what if the entity has an id property? I would expect only the id to be considered in the hash. Since we cant tell which properties are the id imho we should not implement hash or equals.

I see your point, there can be different needs. However i think the most common expected behavior when you're doing equality comparison between two objects, every property is considered, especially in a hashset. And if you need a different equality behavior you would override or separately code it in consumer function.