Return value from mutation is empty and/or undefined

Question

When running an @client mutation using apollo-link-state, then response from the resolver is merely:

{ data: {}, errors: undefined }

From the resolver i'm returning {data: { ...product }}. Where the product is an object with multiple values, among these a __typename.

I have tried setting the return value, to all sorts of values, such as return product, return { data: product }, return { data: { data: { product }}}etc. etc. i think you get the idea.

Resolver:

export const updateInventoryItem = async (product, cache) => {
  const query = gql
    query {
      inventory @client {
        ...omitted, but all the values
    }
   };

   const prevState = await cache.readQuery({ query });
   const prevInventory = prevState.inventory;

   const productIndex = prevInventory.findIndex(x => x.id === 
   product.id);
   prevInventory.splice(productIndex, 1);

   const data = {
    inventory: [
     product,
     ...prevInventory
    ]
   }

  await cache.writeQuery({ query, data });

  return {data: { ...product }}
 }

Mutation:

const UPDATE_ITEM = gql
  mutation updateInventoryItem($product: InventoryItem!) {
    updateInventoryItem(product: $product) @client {
      __typename
      id
      ...and so on
    }
  }
;

The function that calls the mutation:

updateItem = () => {
    this.props.updateItem({
      variables: {
        product: {
          __typename: this.state.item.__typename,
          id: this.state.item.id,
          addedToCart: this.state.item.addedToCart,
          ...and so on
        }
      }
    }).then((e) => {
      console.log(e);
      this.setState({ savedRecently: true })
    },
      err => console.log(err))
  }

Firstly: I'm sorry for the terribly long block of code to plow through.

The expected result of the code above, would be for the resolver to return the product just added, like { data: {...product}, errors: undefined }, but instead it returns { data: {}, errors: undefined } as stated in the beginning.

Please let me know if you need more information, or if i missed something.

Answer 1

const UPDATE_ITEM = gql
  mutation updateInventoryItem($product: InventoryItem!) {
    return updateInventoryItem(product: $product) @client {
      __typename
      id
      ...and so on
    }
  }
;

This function does of course need to return a value, but that's not the whole story here.

GraphQL (Apollo-Client in this case), expects an object formed like the response, you tell it you want.

In this case:

updateInventoryItem(product: $product) @client {
      __typename
      id
      ...and so on
    }

This asks to get an object with a __typename, and id, and whatever else you put in there.

So all in all, a stupid mistake on my part, but since no answers, if anyone falls into the same pit as i did, here's something to try.