net/url: add Values.Has(key)

[iann0036]

There is currently no inbuilt method within Values of detecting whether a query parameter without a value is set (e.g. http://example.com/?queryname).

I propose adding the following method to determine whether a specific key is set:

// Checks whether a given key is set.
func (v Values) IsSet(key string) bool {
	if _, ok := v[key]; ok {
		return true
	}
	return false
}

This would also work for query parameters with values.

[martisch]

Can this be reduced to?

func (v Values) IsSet(key string) bool {
	_, ok := v[key]
	return ok
}

So instead of writing _, ok := v[key] with the proposal v.IsSet(key) would be able to be used instead?

[iann0036]

Yep, that is more concise, I agree.

[rsc]

It seems like the usual Go word is Has for this (HasPrefix, HasSuffix, types.TypeAndValue.HasOk, etc).
Otherwise it seems fine - we typically don't bother and just use the map directly, but we've added all the other operations as methods on Values already.

[rsc]

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

[rsc]

There are 5 thumbs down on the original, but it does seem like this is the one operation that we haven't put into the Values API, and we might as well.

Does anyone object to adding Values.Has? If so, why?

[cristaloleg]

@rsc I suppose it's due to naming, Has (as you've mentioned above) is more natural for Go.

[rsc]

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

[rsc]

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

[gopherbot]

Change https://golang.org/cl/314850 mentions this issue: net/url: add Values.Has