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tpl/collections: Fix union when the first slice is empty
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Fixes #3686
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bep committed Jul 8, 2017
1 parent 7bcc1ce commit dbbc5c4
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Showing 2 changed files with 16 additions and 0 deletions.
9 changes: 9 additions & 0 deletions tpl/collections/collections.go
Original file line number Diff line number Diff line change
Expand Up @@ -494,6 +494,7 @@ type intersector struct {
}

func (i *intersector) appendIfNotSeen(v reflect.Value) {

vi := v.Interface()
if !i.seen[vi] {
i.r = reflect.Append(i.r, v)
Expand Down Expand Up @@ -565,6 +566,14 @@ func (ns *Namespace) Union(l1, l2 interface{}) (interface{}, error) {
}
}

if !l1vv.IsValid() {
// The first slice may be empty. Pick the first value of the second
// to use as a prototype.
if l2v.Len() > 0 {
l1vv = l2v.Index(0)
}
}

for j := 0; j < l2v.Len(); j++ {
l2vv := l2v.Index(j)

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7 changes: 7 additions & 0 deletions tpl/collections/collections_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -666,6 +666,13 @@ func TestUnion(t *testing.T) {
{pagesVals{p1v}, pagesVals{p3v, p3v}, pagesVals{p1v, p3v}, false},
{[]interface{}{p1, p4}, []interface{}{p4, p2, p2}, []interface{}{p1, p4, p2}, false},
{[]interface{}{p1v}, []interface{}{p3v, p3v}, []interface{}{p1v, p3v}, false},
// #3686
{[]interface{}{p1v}, []interface{}{}, []interface{}{p1v}, false},
{[]interface{}{}, []interface{}{p1v}, []interface{}{p1v}, false},
{pagesPtr{p1}, pagesPtr{}, pagesPtr{p1}, false},
{pagesVals{p1v}, pagesVals{}, pagesVals{p1v}, false},
{pagesPtr{}, pagesPtr{p1}, pagesPtr{p1}, false},
{pagesVals{}, pagesVals{p1v}, pagesVals{p1v}, false},

// errors
{"not array or slice", []string{"a"}, false, true},
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