fix: find proper parent when sizedFields parent is a non-list wrapper

[ysmolski]

Instead of just trying the parent of the fields specifed in the sizedFields and failing on non-list wrapper, find nearest list-typed ancestor to avoid double counting of nested lists.

Closes #1492

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📥 Commits

Reviewing files that changed from the base of the PR and between 31e7111 and 8d13dea.

📒 Files selected for processing (1)

• execution/engine/execution_engine_cost_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• execution/engine/execution_engine_cost_test.go

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📝 Walkthrough

Walkthrough

This PR fixes actual cost inflation when a non-list wrapper field is annotated with @listSize and contains sizedFields. The fix changes how the cost calculation finds the parent list size: instead of trimming the JSON path string, it walks the node parent chain to find the nearest list-returning ancestor. Supporting refactoring extracts the root coordinate to a constant, and a regression test validates the fix.

Changes

Cost Calculation Fix for Non-List Wrapper Parents

Layer / File(s)	Summary
List parent lookup refactor in cost calculation v2/pkg/engine/plan/cost.go	The actual cost multiplier calculation for list-returning fields now traverses the CostTreeNode parent chain to locate the nearest ancestor with returnsListType==true, then reads actualListSizes from that ancestor's jsonPath, instead of using string-based path prefix trimming.
Root coordinate constant extraction v2/pkg/engine/plan/cost_visitor.go	Introduces a package-level costTreeRootNodeCoords variable to hold the sentinel FieldCoordinate and replaces its inline literal usage in NewCostVisitor.
Regression test for non-list wrapper sizedFields execution/engine/execution_engine_cost_test.go	Adds a test case validating that a non-list wrapper field (items_page) with @listSize over a list parent (boards) computes both estimated and actual cost as 120, confirming the fix prevents cost inflation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: fixing parent detection when sizedFields parent is a non-list wrapper.
Description check	✅ Passed	The description is related to the changeset, explaining the problem (double counting) and the solution (find nearest list-typed ancestor).
Linked Issues check	✅ Passed	The changes directly address issue #1492 by modifying cost.go to walk up parent chain to find nearest list ancestor, implemented in cost_visitor.go and tested in cost_test.go.
Out of Scope Changes check	✅ Passed	All changes are scoped to cost calculation logic and its tests; no unrelated modifications are present.

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