Use iter.Seq to iterate over ScanIterator

[khasanovbi]

Support for native iterators has been added in go 1.23.
New Vals method added that return keys iterator directly instead of keys through Next, Val pair.
Minimum go version changed to 1.23.

[khasanovbi]

#3347

[khasanovbi]

Hmm, interesting why json tests failed...

[ndyakov]

@khasanovbi thank you for the suggestion, we were looking into updating the go versions but observed that some tests were failing. We didn't have the time to look more into it back then. Since you decided to try, let's directly update to 1.24 and figure out the tests.
I also have some reservation about marking the Next and Val as deprecated. You can see them in my comment. I am curious about what you think.

[ndyakov]

The Vals itself will be using Next. In general I would vote agains marking those as deprecated since they will continue to be used inside the library and if a developer would prefer to use them instead of the Vals I don't think we should discourage that by marking Next and Val as deprecated.
Let me know what you think.

[khasanovbi]

I think iterator via Vals is easier and more convenient than the combination Next, Val.

When you use Val, you need to know that Next must be called before it.
When you use Vals, you just iterate through the values.

Also the code of Vals could be much simpler without calls of Next, Val, without pos var handling, without extra cmd.Err check at each Val call.

// Vals returns iterator over key/field at the current cursor position.
func (it *ScanIterator) Vals(ctx context.Context) iter.Seq[string] {
	return func(yield func(string) bool) {
		if it.cmd.Err() != nil {
			return
		}

		for {
			for _, val := range it.cmd.page {
				if !yield(val) {
					return
				}
			}

			// Return if there is no more data to fetch.
			if it.cmd.cursor == 0 {
				return
			}

			// Fetch next page.
			var cursorIndex int
			switch it.cmd.args[0] {
			case "scan", "qscan":
				cursorIndex = 1
			default:
				cursorIndex = 2
			}

			it.cmd.args[cursorIndex] = it.cmd.cursor

			err := it.cmd.process(ctx, it.cmd)
			if err != nil {
				return
			}
		}
	}
}

they will continue to be used inside the library

In PR Next, Val is used only at this place, I left them in for backward compatibility only.

[ndyakov]

I don't disagree that an Iterator is more ergonomic. What I wanted to make sure is that we do not deprecate the current way of iterating over the values before version 10 of go-redis. If you feel strongly about deprecating, we can postpone this PR for when go-redis/v10 will be released.