Error calling buildSubgraphSchema: TypeError: type.getInterfaces is not a function

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1

I’m using version 0.1.4 of @apollo/subgraph.

My schema includes an interface, and I’m getting the following error when calling buildSubgraphSchema:

TypeError: type.getInterfaces is not a function 
at printImplementedInterfaces node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:174:27) 
at printInterface node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:219:5) 
at printType node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:149:12) 
at node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:78:30 
at Array.map (<anonymous>) 
at printFilteredSchema node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:78:16) 
at printSubgraphSchema node_modules\@apollo\subgraph\src\printSubgraphSchema.ts:41:10) 
at buildSubgraphSchema node_modules\@apollo\subgraph\src\buildSubgraphSchema.ts:81:34)

Looking at the apollo/subsgraph source (printSubgraph.ts), the following method looks odd - why would printing an interface include printing which interfaces that interface supports? I didn’t think GraphQL allowed interface A implements B.

function printInterface(type: GraphQLInterfaceType): string {
  // Apollo change: print `extend` keyword on type extensions.
  // See printObject for assumptions made.
  //
  // XXX revist extension checking
  const isExtension =
    type.extensionASTNodes && type.astNode && !type.astNode.fields;

  return (
    printDescription(type) +
    // Apollo change: print `extend` keyword on interface extensions
    (isExtension ? 'extend ' : '') +
    `interface ${type.name}` +
    printImplementedInterfaces(type) +   // <-- why this?
    printFederationDirectives(type) +
    printKnownDirectiveUsagesOnTypeOrField(type) +
    printFields(type)
  );
}

The error occurs then in the printImplementedInterfaces method because a GraphQLInterfaceType does not have a method getInterfaces():

function printImplementedInterfaces(
  type: GraphQLObjectType | GraphQLInterfaceType,
): string {
  const interfaces = type.getInterfaces(); // <-- This blows up
  return interfaces.length
    ? ' implements ' + interfaces.map((i) => i.name).join(' & ')
    : '';
}

I can’t believe I’m the first person to build a subgraph schema with an interface in it, so is there something I might have done wrong here?

2

Just in case anyone else hits this, the problem turned out to be the fact that I was attempting to add subgraph functionality into an Apollo v2 server, so the dependencies were way out of date. Migrating my server to Apollo v3 made the error go away.