#3997 test(cypher): regression tests for collect(r)+VLP row-drop bug

[robfrank]

$(cat <<'EOF'

Summary

Closes #3997.

Adds regression tests for the scenario where collect(r) is carried via WITH and a later MATCH uses a variable-length path (VLP) - previously causing all rows to be dropped.

• collectRelThenVlpReturnsRows - basic collect(r) AS rels + VLP returns 2 rows (len=1 and len=2)
• collectDistinctRelThenVlpReturnsRows - OPTIONAL MATCH + collect(DISTINCT r) + VLP (the "stronger variant" from the issue) returns 2 rows
• collectScalarThenVlpReturnsRows - control case: collect(type(r)) continues to work

Root cause and fix

The bug was caused by ExpandPathStep.hasEdgeConflict() treating List<Edge> values (from collect(r)) as same-MATCH bound relationships, blocking all VLP paths when those edges appeared in the traversal.

The fix was already merged in commit d58bf7b1c (issue #3999), which introduced the previousStepVariables mechanism in ExpandPathStep. After WITH a, collect(r) AS rels, boundVariables = {a, rels}. When the second MATCH VLP runs, previousStepVariables = {a, rels}, so rels is correctly skipped in the conflict check.

Test plan

• collectRelThenVlpReturnsRows passes - primary bug scenario
• collectDistinctRelThenVlpReturnsRows passes - OPTIONAL MATCH + collect(DISTINCT r) variant
• collectScalarThenVlpReturnsRows passes - control case (scalar collect)
• All existing OpenCypherVariableLengthPathTest tests pass (3 pre-existing + 3 new = 6 total)
• All existing Issue3999RelVarLostAfterVarLengthMatchTest tests pass (6 total)

🤖 Generated with Claude Code
EOF
)

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Coverage ∅ diff coverage · -8.53% coverage variation

Metric	Results
Coverage variation	✅ -8.53% coverage variation
Diff coverage	✅ ∅ diff coverage

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Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (63ec984)	120069	88599	73.79%
Head commit (5f23c65)	151308 (+31239)	98747 (+10148)	65.26% (-8.53%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#4010)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[gemini-code-assist]

Code Review

This pull request introduces three new test cases to OpenCypherVariableLengthPathTest.java to address Issue #3997, specifically testing the interaction between collect() and variable-length paths in OpenCypher queries. The review feedback suggests wrapping the database.query() calls in try-with-resources blocks to ensure that the ResultSet is properly closed and database resources are released.

[gemini-code-assist]

The ResultSet should be closed to prevent potential resource leaks. This also applies to the other new test cases in this PR.

Suggested change

	database.query("opencypher",
	"""
	MATCH (a:Person {name: 'Alice'})
	OPTIONAL MATCH (a)-[r:KNOWS]->(b:Person)
	WITH a, collect(DISTINCT r) AS rels
	MATCH path = (a)-[:KNOWS*1..2]->(c:Person)
	RETURN length(path) AS len, size(rels) AS relationCount
	ORDER BY len""").forEachRemaining(rows::add);
	try (final ResultSet resultSet = database.query("opencypher",
	"""
	MATCH (a:Person {name: 'Alice'})
	OPTIONAL MATCH (a)-[r:KNOWS]->(b:Person)
	WITH a, collect(DISTINCT r) AS rels
	MATCH path = (a)-[:KNOWS*1..2]->(c:Person)
	RETURN length(path) AS len, size(rels) AS relationCount
	ORDER BY len""")) {
	resultSet.forEachRemaining(rows::add);
	}

[robfrank]

Fixed in 5f23c65 - all three new test methods now wrap the ResultSet in try-with-resources.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.22%. Comparing base (63ec984) to head (5f23c65).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4010      +/-   ##
==========================================
- Coverage   64.78%   64.22%   -0.57%     
==========================================
  Files        1597     1597              
  Lines      120069   120069              
  Branches    25557    25557              
==========================================
- Hits        77790    77115     -675     
- Misses      31500    32280     +780     
+ Partials    10779    10674     -105     

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