[aepod]

This is a fresh version of #292 on current main, and replaces it. #484 fixed #269, so RETURN now iterates every MATCH row. Thanks for that. This PR builds on it and fixes what was still missing.

I ran the tests from #292 against current main and 2 of them still fail. There are four remaining problems, each reproduced on current main with a new test before the fix:

1. A MATCH with zero matches makes RETURN n error with VariableNotFound("n") instead of returning 0 rows. RETURN falls back to the outer context when matched_rows is empty.
2. RETURN n.name gets the column name ?column?, and RETURN n.name, n.city collapses both into one ?column? column.
3. MATCH ... SET n.x = ... and MATCH ... DETACH DELETE n do nothing, because SET and DELETE read the variable from the outer context, which MATCH no longer fills.
4. MATCH (p:Person), (c:Company) unions the two pattern results instead of taking a cross product, so RETURN p.name, c.name errors with VariableNotFound("p").

The fix:

• The executor tracks whether a MATCH ran. This is a private field on Executor, so there is no public API change.
• RETURN, SET and DELETE share one row_contexts() helper.
• Property items get var.prop column names. Aliases still win.
• Comma patterns combine as a cross product, and a variable shared between patterns must bind the same element.
• DELETE removes each node or edge once, even if it appears in several rows.

Files: crates/rvlite/src/cypher/executor.rs and crates/rvlite/src/cypher/mod.rs.

Tests: with only the new tests applied to current main, 7 of the 13 tests in cypher::tests fail: test_match_no_results, test_match_return_properties, test_match_where_filter (it now checks the n.name values), test_return_multiple_property_columns, test_match_set_updates_every_row, test_match_detach_delete_every_row, test_match_comma_patterns_cross_product. With this change:

• cargo test -p rvlite --no-fail-fast: lib 72 passed, 0 failed, 2 ignored (the parser ignores that were already there). cypher_integration_test 8 passed.
• cargo fmt check is clean on the changed files.
• cargo clippy -p rvlite --all-targets: 0 warnings in rvlite, same as main.
• cargo check -p rvlite --target wasm32-unknown-unknown passes.

Not fixed here:

• A second MATCH statement still replaces the first one's rows.
• MATCH (n:A:B) still gives duplicates.
• Plain DELETE (without DETACH) still always errors for nodes, as before.

This touches crates/rvlite/src/cypher/mod.rs, like open PR #1084. I checked with git merge-tree and there is no textual conflict.

🤖 Generated with RuFlo