Apollo GraphQL client doesn't return cached nested types in a query - apollo

Question

I'm performing a query to get PowerMeter details in which contains another type inside called Project. I write the query this way:
query getPowerMeter($powerMeterId: ID!) {
powerMeter: powerMeter(powerMeterId: $powerMeterId) {
id
name
registry
project {
id
name
}
}
}
When I perform the query for the first time, project is successfully returned. The problem is that when I perform subsequent queries with the same parameters and default fetchPolicy (cache-first), project isn't returned anymore.
How may I solve this problem?
Also, I call readFragment to check how powerMeter is saved in the cache and the response shows that powerMeter has project saved.
const frag = client.readFragment({
fragment: gql`
fragment P on PowerMeter {
id
name
registry
project {
id
name
}
}
`,
id: 'PowerMeter:' + powerMeterId,
});
Power Meter returned first time
{
"powerMeter":{
"id":"7168adb4-4198-443e-ab76-db0725be2b18",
"name":"asd123123",
"registry":"as23",
"project":{
"id":"41d8e71b-d1e9-41af-af96-5b4ae9e492c1",
"name":"ProjectName",
"__typename":"Project"
},
"__typename":"PowerMeter"
}
}
Fragment after calling power meter first time
{
"id":"7168adb4-4198-443e-ab76-db0725be2b18",
"name":"asd123123",
"registry":"as23",
"project":{
"id":"41d8e71b-d1e9-41af-af96-5b4ae9e492c1",
"name":"ProjectName",
"__typename":"Project"
},
"__typename":"PowerMeter"
}
Power Meter returned second time
{
"powerMeter":{
"id":"7168adb4-4198-443e-ab76-db0725be2b18",
"name":"asd123123",
"registry":"as23",
"__typename":"PowerMeter"
}
}
Fragment after calling power meter second time
{
"id":"7168adb4-4198-443e-ab76-db0725be2b18",
"name":"asd123123",
"registry":"as23",
"project":{
"id":"41d8e71b-d1e9-41af-af96-5b4ae9e492c1",
"name":"ProjectName",
"__typename":"Project"
},
"__typename":"PowerMeter"
}
Edit 1: Fetching Query
The code below is how I'm fetching data. I'm using useApolloClient and not a query hook because I'm using AWS AppSync and it doesn't support query hook yet.
import { useApolloClient } from '#apollo/react-hooks';
import gql from 'graphql-tag';
import { useEffect, useState } from 'react';
export const getPowerMeterQuery = gql`
query getPowerMeter($powerMeterId: ID!) {
powerMeter: powerMeter(powerMeterId: $powerMeterId) {
id
name
registry
project {
id
name
}
}
}
`;
export const useGetPowerMeter = (powerMeterId?: string) => {
const client = useApolloClient();
const [state, setState] = useState<{
loading: boolean;
powerMeter?: PowerMeter;
error?: string;
}>({
loading: true,
});
useEffect(() => {
if (!powerMeterId) {
return setState({ loading: false });
}
client
.query<GetPowerMeterQueryResponse, GetPowerMeterQueryVariables>({
query: getPowerMeterQuery,
variables: {
powerMeterId,
},
})
.then(({ data, errors }) => {
if (errors) {
setState({ loading: false, error: errors[0].message });
}
console.log(JSON.stringify(data));
const frag = client.readFragment({
fragment: gql`
fragment P on PowerMeter {
id
name
registry
project {
id
name
}
}
`,
id: 'PowerMeter:' + powerMeterId,
});
console.log(JSON.stringify(frag));
setState({
loading: false,
powerMeter: data.powerMeter,
});
})
.catch(err => setState({ loading: false, error: err.message }));
}, [powerMeterId]);
return state;
};
Edit 2: Fetching Policy Details
When I use fetchPolice equals cache-first or network-only, the error persists. When I use no-cache, I don't get the error.

Answer 1

I think this might have been the solution:
https://github.com/apollographql/apollo-client/issues/7050
Probably way too late, but it could help people coming to this issue in the future.
When using apollo client's InMemoryCache it seems you need to provide a list of possible types so the fragment matching can be done correctly when using the InMemoryCache.
You can do that manually when having few union types and a pretty stable API which doesn't change very often.
Or you automatically generate these types into a json file, which you can use directly in the InMemoryCache's possibleTypes config directly.
Visit this link to the official docs to find out how to do it.
Cheers.