feat: enable to ignore cost weights on implementing types

[ysmolski]

This PR adds a feature flag that allows to emulate behavior
of Apollo that ignored weights on implementing types when
the fields on interface does not have cost weight assigned.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between 507f612 and 89e8ecf.

📒 Files selected for processing (2)

• execution/engine/execution_engine_cost_test.go
• v2/pkg/engine/plan/cost.go

🚧 Files skipped from review as they are similar to previous changes (2)

• v2/pkg/engine/plan/cost.go
• execution/engine/execution_engine_cost_test.go

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📝 Walkthrough

Walkthrough

Adds IgnoreImplementingTypeWeights to Configuration, stores it in CostCalculator, and threads it through costInput as ignoreImplementingTypeWeights. Two guard conditions in costsAndMultiplier disable implementing-type field weight and directive argument weight resolution when the flag is set. newCostInput is refactored to accept *CostCalculator directly, and defaultListSize is floored to 1. Engine-level test harness and a full suite of cost test cases are added.

Changes

IgnoreImplementingTypeWeights feature

Layer / File(s)	Summary
Configuration field and CostCalculator storage v2/pkg/engine/plan/configuration.go, v2/pkg/engine/plan/cost.go	Adds IgnoreImplementingTypeWeights bool to Configuration and stores it in CostCalculator.ignoreImplementingTypeWeights; NewCostCalculator also floors defaultListSize to at least 1 via max.
costInput refactor and costsAndMultiplier gates v2/pkg/engine/plan/cost.go	Refactors newCostInput to accept *CostCalculator and wires ignoreImplementingTypeWeights into costInput; two conditions in costsAndMultiplier (field weight resolution and directive argument weight summation) are gated on the new flag; DebugPrint input construction is updated to the new signature.
Test harness option and engine-level tests execution/engine/execution_engine_test.go, execution/engine/execution_engine_cost_test.go	Adds ignoreImplementingTypeWeights field to _executionTestOptions, wires it into plannerConfig in runExecutionTest, adds costsIgnoreImplementingTypeWeights() helper, and introduces the skipImplementingTypesOnAbstract suite covering abstract-only, concrete fragment, assumedSize list, named fragment, and interface-field regression scenarios.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• wundergraph/graphql-go-tools#1465: Adds directive-argument weight handling across implementing fields on abstract paths in cost.go, directly in the same logic paths this PR now gates with the new flag.
• wundergraph/graphql-go-tools#1521: Modifies abstract cost aggregation in cost.go to avoid double-counting based on TypeNameStats, intersecting with the same implementing-type weight resolution code this PR conditionally skips.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat: enable to ignore cost weights on implementing types' clearly summarizes the main change, which adds a feature flag to ignore cost weights on implementing types.
Description check	✅ Passed	The description explains that the PR adds a feature flag to emulate Apollo's behavior of ignoring weights on implementing types when interface fields lack cost weights, which aligns with the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Commit unit tests in branch yury/eng-9569-interface-field-cost-uses-max-across-implementations-instead

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@v2/pkg/engine/plan/cost.go`:
- Around line 589-590: The actual-cost path for abstract-list normalization is
not respecting the skipImplementingTypesOnAbstract flag. In the section around
line 775 where implementing field weights are read (around lines 790-794), add a
check to skip reading implementing field weights when
skipImplementingTypesOnAbstract is enabled, similar to how it's checked at line
589. Additionally, add a regression test that sets
IgnoreImplementingTypeWeights=true with an abstract-list child field containing
non-zero default type or scalar weights, then verify that implementing field
weights remain zero in actual-cost mode and are not reintroduced despite the
non-zero defaults.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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📥 Commits

Reviewing files that changed from the base of the PR and between 6a5eb1a and 507f612.

📒 Files selected for processing (4)

• execution/engine/execution_engine_cost_test.go
• execution/engine/execution_engine_test.go
• v2/pkg/engine/plan/configuration.go
• v2/pkg/engine/plan/cost.go