fix: fallback to abstract name if no __typename was sent

[ysmolski]

Testing in cosmo revealed this issue.

[claude]

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Reviewing files that changed from the base of the PR and between 9fa4c82 and 39d843d.

📒 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

recordObjectTypeStats now records type-name distribution statistics for abstract objects even when subgraphs omit __typename by falling back to the declared abstract type name; a regression test verifies cost accounting for an abstract field returned without __typename.

Changes

Type Stats Recording for Abstract Types

Layer / File(s)	Summary
Type stats fallback to declared type name v2/pkg/engine/resolve/resolvable.go	The early-return guard is narrowed to skip only when the object path is empty or the node is not abstract. When updating stats.TypeNames, the code uses obj.TypeName if the runtime typeName is nil, otherwise it uses the runtime __typename, before incrementing the distribution.
Regression test: abstract field without __typename execution/engine/execution_engine_cost_test.go	Adds a subtest to TestExecutionEngine_Cost that returns an abstract hero without __typename, configures per-type weights for implementing types, and asserts both estimated and actual cost equal 13 for Query.hero.

🎯 3 (Moderate) | ⏱️ ~20 minutes

• wundergraph/graphql-go-tools#1512: Related test updates that adjust cost assertions for abstract/interface field execution.
• wundergraph/graphql-go-tools#1521: Related changes addressing how abstract type runtime distributions are recorded/used for cost accounting.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: falling back to abstract type name when __typename is missing from subgraph responses.
Description check	✅ Passed	The description, though brief, is directly related to the changeset by referencing the issue discovered during testing that prompted the fix.
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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