Use MultiMap instead of HashMap for the parsed query params

[havarnov]

Use multimap for the parsed query params instead of HashMap<String, Vec<String>>.

Mulitmap is basically a thin wrapper around HashMap<T, Vec<T>>, but with (imo) a bit better api for using the values. Especially for the common use case of only having one value per key. E.g.:

let params: HashMap<String, Vec<String>> = HashMap::new();
let val = params["key"][0];
for (key, vec_of_val) in params {...}

let params: MultiMap<String, String> = MultiMap::new();
let val = params["key"];
for (key, val) in params.iter() {...}
for (key, vec_of_val) in params.iter_all() {...}

[reem]

If multimap can provide the flexibility of the full HashMap API (I am mostly concerned about iterators and the entry API in particular) then I am open to this.

[untitaker]

I think the additional methods provided by multimap could be provided by a trait that is impl'd for HashMap<K, Vec<V>>, not a wrapper. This would provide full backwards compat, urlencoded wouldn't have to depend on multimap, and no typesig would have to be changed.

[havarnov]

I don't see how you could implement for example .get(key) which returns Some(val)|None and not the whole vector, but maybe I'm missing something. And that is IMO the biggest win because the most common case is only having one value per key.

The "custom" iterators could probably be implemented as a trait though.

[untitaker]

You'd have to rename it to get_only or use it directly from the trait to avoid nameclashes. That's part of backwards compat.

[untitaker]

@havarnov any update on this? Would you consider changing your multimap crate in such a way, or should I write my own version?

[untitaker]

Also missing voice of @reem

[reem]

My thoughts haven't really changed, if the API is as good as HashMap I am leaning towards it.

[havarnov]

Havn't had time to look at think about this. I don't want to make MultiMap less convinent because that's the whole point. Hmm, let med look at it through the weekend.

[havarnov]

Sorry for the radio silence, haven't had time to look into this before now. I've made a version which uses MultiMap instead of HashMap: https://github.com/havarnov/urlencoded/tree/feat/multimap. Maybe it's easier to compare the options now..