bug in WhereIndexed

[quexer]

I believe WhereIndexed doesn't work as design:

https://play.golang.org/p/HD5-rxIkpx0

package main

import (
	"fmt"

	"github.com/ahmetb/go-linq/v3"
)

func main() {

	r := linq.Range(1, 10).
		WhereIndexed(func(i int, _ interface{}) bool {
			return i%3 == 0
		}).
		Results()
	fmt.Println(r)
}

output of the code above is
[1 2 3 4 5 6 7 8 9 10]
instead of
[3 6 9]

maybe the bug is here

https://github.com/ahmetb/go-linq/blob/master/where.go#L61

thanks!

[ahmetb]

Hmm this looks legitimate. So you're saying this is a variable reused unintentionally?

Do you mind adding a test case for it so we can clearly see this fail. I'm also surprised we don't have such a case unit tested already.

[quexer]

hi, here's the test case:

I think index behavior should be the same no matter what predicate is provided. otherwise, we could not do index-based filtering with WhereIndexed

thanks

package main

import (
	"testing"

	"github.com/ahmetb/go-linq/v3"
)

var l = []string{"a", "b", "c", "d"}

// this will fail
func TestWhereIndexedWithTruePredicate(t *testing.T) {
	var idx int
	linq.From(l).WhereIndexed(func(i int, _ interface{}) bool {
		if i != idx {
			t.Errorf("i should be increased like idx in WhereIndexed with true predicate. expected(%v), got(%v)", idx, i)
		}
		idx++
		return true
	}).Results()
}

// this will pass
func TestWhereIndexedWithFalsePredicate(t *testing.T) {
	var idx int
	linq.From(l).WhereIndexed(func(i int, _ interface{}) bool {
		if i != idx {
			t.Errorf("i should be increased like idx in WhereIndexed with false predicate. expected(%v), got(%v)", idx, i)
		}
		idx++
		return false
	}).Results()
}

// suppose there's no different between ForEachIndexed and WhereIndexed as for index behavior
// this will pass
func TestForEachIndexed(t *testing.T) {
	var idx int
	linq.From(l).ForEachIndexed(func(i int, _ interface{}) {
		if i != idx {
			t.Errorf("i should be increased like idx in ForEachIndexed. expected(%v), got(%v)", idx, i)
		}
		idx++
	})
}

[ahmetb]

hi, here's the test case:

sorry I meant to say, can you send a PR with this test case?

[ahmetb]

go-linq/where_test.go

Line 32 in b1b02a1

func TestWhereIndexed(t *testing.T) {

for example we have this test case, you can add it next to that.
also do you have any idea why this test case passes? sorry I'm rusty a bit on this codebase.

[quexer]

hi @ahmetb , here's the PR:

#87

what I'm confused is all about the picture below

[ahmetb]

Yeah I'm surprised the [9]int{1, 1, 1, 2, 1, 2, 3, 4, 2} test is passing but yours in #87 isn't.

The part you highlighted seems accurate. First param passed to predicate is the index of element (starting from 0) in the collection, second param is its value.

[quexer]

If the highlighted part is accurate, then I'm sure there's bug in WhereIndexed