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fix(composition): Handle output type covariance properly in satisfiability #3277

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sachindshinde merged 2 commits into from
Jun 24, 2025
Merged

fix(composition): Handle output type covariance properly in satisfiability #3277

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790844d
Fix satisfiability bugs around output type covariance
sachindshinde Jun 16, 2025
fdecbd1
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sachindshinde Jun 24, 2025
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3 changes: 2 additions & 1 deletion composition-js/src/validate.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -641,6 +641,7 @@ export class ValidationState {
for (const pathInfo of this.subgraphPathInfos) {
const tailSubgraphName = pathInfo.path.path.tail.source;
const tailSubgraphEnumValue = subgraphNameToGraphEnumValue.get(tailSubgraphName);
const tailTypeName = pathInfo.path.path.tail.type.name;
const entryKeys = [];
const contexts = Array.from(pathInfo.contexts.entries());
contexts.sort((a, b) => a[0].localeCompare(b[0]));
Expand All @@ -649,7 +650,7 @@ export class ValidationState {
entryKeys.push(`${context}=${subgraphEnumValue}.${typeName}`);
}
subgraphContextKeys.add(
`${tailSubgraphEnumValue}[${entryKeys.join(',')}]`
`${tailSubgraphEnumValue}.${tailTypeName}[${entryKeys.join(',')}]`
);
}
return subgraphContextKeys;
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9 changes: 9 additions & 0 deletions query-graphs-js/src/graphPath.ts
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Expand Up @@ -1735,6 +1735,15 @@
// We can now continue on dealing with the actual field.
}

if (
transition.kind === 'DownCast'
&& transition.castedType.name === path.tail.type.name

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) {
// Due to output type covariance, a downcast supergraph transition may be a no-op on the
// subgraph path. In these cases, we effectively ignore the type condition.
return [path];

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}

const options: GraphPath<Transition, V>[] = [];
const deadEndClosures: UnadvanceableClosure[] = [];

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