fix: array traversal drops streaming indices from variable binding

[lawrence3699]

Fixes #2593

Problem

When streaming values pipe into an array traversal with a bound variable, only the first index is used. For example:

$ echo '["a","b"]' | yq '. as $o | keys[] | $o[.]'
a
# expected: a, b

The workaround of adding an intermediate variable binding (. as $k |) works, but shouldn't be necessary:

$ echo '["a","b"]' | yq '. as $o | keys[] | . as $k | $o[.]'
a
b

Root cause

In traverseArrayOperator, the RHS collect expression is evaluated with the full streaming context. When EvaluateTogether is false (the default for streaming values), the collect operator creates a separate SequenceNode per streaming value. Line 126 then only takes the first SequenceNode's content, discarding the indices from all other streaming values.

Fix

When the RHS produces more SequenceNodes than the LHS has matching nodes (i.e., the LHS is a single bound variable but the index varies per streaming value), traverse each set of indices separately against the full LHS.

Before/After

# Before
$ echo '["a","b"]' | yq '. as $o | keys[] | $o[.]'
a

# After
$ echo '["a","b"]' | yq '. as $o | keys[] | $o[.]'
a
b

Works for both arrays and maps:

$ echo '{"x":"a","y":"b"}' | yq '. as $o | keys[] | $o[.]'
a
b

Testing

Added three regression tests covering arrays, maps, and longer sequences. Full test suite passes:

ok  github.com/mikefarah/yq/v4          0.353s
ok  github.com/mikefarah/yq/v4/cmd      0.447s
ok  github.com/mikefarah/yq/v4/pkg/yqlib 0.491s
ok  github.com/mikefarah/yq/v4/test     0.468s

[Copilot]

Pull request overview

Fixes a streaming/traversal mismatch in traverseArrayOperator where array/map indexing via a bound variable (e.g. $o[.]) would only use the first streamed index set, dropping subsequent indices from the stream.

Changes:

• Update traverseArrayOperator to traverse the LHS against each per-stream RHS index set when the RHS yields multiple collected sequences.
• Add regression tests covering arrays, maps, and longer sequences for the $o[.] streaming-keys case.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/yqlib/operator_traverse_path.go	Adjusts traversal logic to handle multiple RHS “collected index” sequences without dropping streamed indices.
pkg/yqlib/operator_traverse_path_test.go	Adds regression scenarios ensuring streaming keys[] indices correctly traverse bound variables for arrays/maps.

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[Copilot]

The new branch is intended to handle the case where the LHS is a single node (e.g. a bound variable), but the condition lhs.MatchingNodes.Len() < rhs.MatchingNodes.Len() can also be true when the LHS has multiple matches (e.g. 2 LHS nodes, 3 RHS sequences). In that case this code traverses each RHS index set against all LHS nodes, which can introduce an unintended cross-product of results. Consider tightening the condition to explicitly guard on lhs.MatchingNodes.Len() == 1 (or <= 1) so the multi-RHS traversal only applies to the intended bound-variable scenario.