fix: traverse array with streaming indices from variable binding

When streaming values (e.g. from keys[]) pipe into an array
traversal like $o[.], only the first streaming index was used.

The RHS collect expression produces a separate SequenceNode per
streaming value when EvaluateTogether is false. The existing code
at line 126 only took the first SequenceNode, discarding the rest.

When the LHS is a single bound variable and the RHS has multiple
index sets, traverse each set separately.

Fixes #2593

pkg/yqlib/operator_traverse_path.go

@@ -123,6 +123,27 @@ func traverseArrayOperator(d *dataTreeNavigator, context Context, expressionNode
 	if expressionNode.Operation.Preferences != nil {
 		prefs = expressionNode.Operation.Preferences.(traversePreferences)
 	}
+
+	// When streaming values produce per-value index sets in the RHS and the LHS
+	// is a single node (e.g. a bound variable), traverse the LHS with each
+	// index set separately. Without this, only the first set of indices is used
+	// and the rest are silently dropped.
+	if rhs.MatchingNodes.Len() > 1 && lhs.MatchingNodes.Len() < rhs.MatchingNodes.Len() {
+		var allResults = list.New()
+		for el := rhs.MatchingNodes.Front(); el != nil; el = el.Next() {
+			seqNode := el.Value.(*CandidateNode)
+			if seqNode.Kind != SequenceNode {
+				continue
+			}
+			result, err := traverseNodesWithArrayIndices(lhs, seqNode.Content, prefs)
+			if err != nil {
+				return Context{}, err
+			}
+			allResults.PushBackList(result.MatchingNodes)
+		}
+		return context.ChildContext(allResults), nil
+	}
+
 	var indicesToTraverse = rhs.MatchingNodes.Front().Value.(*CandidateNode).Content
 
 	log.Debugf("indicesToTraverse %v", len(indicesToTraverse))

pkg/yqlib/operator_traverse_path_test.go

@@ -132,6 +132,38 @@ var badTraversePathOperatorScenarios = []expressionScenario{
 }
 
 var traversePathOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:     true,
+		description: "traverse array with streaming indices from keys",
+		document:    `["a","b"]`,
+		expression:  `. as $o | keys[] | $o[.]`,
+		expected: []string{
+			"D0, P[0], (!!str)::a\n",
+			"D0, P[1], (!!str)::b\n",
+		},
+	},
+	{
+		skipDoc:     true,
+		description: "traverse map with streaming indices from keys",
+		document:    `{x: "a", y: "b"}`,
+		expression:  `. as $o | keys[] | $o[.]`,
+		expected: []string{
+			"D0, P[x], (!!str)::a\n",
+			"D0, P[y], (!!str)::b\n",
+		},
+	},
+	{
+		skipDoc:     true,
+		description: "traverse longer array with streaming indices from keys",
+		document:    `["a","b","c","d"]`,
+		expression:  `. as $o | keys[] | $o[.]`,
+		expected: []string{
+			"D0, P[0], (!!str)::a\n",
+			"D0, P[1], (!!str)::b\n",
+			"D0, P[2], (!!str)::c\n",
+			"D0, P[3], (!!str)::d\n",
+		},
+	},
 	{
 		skipDoc:     true,
 		description: "strange map with key but no value",