[Data masking] Fix bug where masked field could be returned in parent query

[jerelmiller]

Because we try and retain object identities as much as possible when running the data masking algorithm, this causes an issue where would-be masked fields are returned in the query when a named fragment selects additional fields on the same child selection as the query.

For example, take this query:

query {
  user {
    profile {
      id
    }
    ...UserFields
  }
}

fragment UserFields on User {
  profile {
    id
    age
  }
}

Here the parent asks only for the id on the profile field while the UserFields fragment selects age on profile as well. Prior to this fix, both id and age were returned as part of the parent query even though age should have been masked. This fix ensures age would be masked here as expected.

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[github-actions]

size-limit report 📦

Path	Size
dist/apollo-client.min.cjs	39.89 KB (+1.44% 🔺)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/main.cjs"	49.05 KB (+2.2% 🔺)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/main.cjs" (production)	46.18 KB (+1.34% 🔺)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/index.js"	35.45 KB (+3.05% 🔺)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/index.js" (production)	32.88 KB (+1.87% 🔺)
import { ApolloProvider } from "dist/react/index.js"	1.26 KB (0%)
import { ApolloProvider } from "dist/react/index.js" (production)	1.24 KB (+0.16% 🔺)
import { useQuery } from "dist/react/index.js"	5.21 KB (-0.02% 🔽)
import { useQuery } from "dist/react/index.js" (production)	4.3 KB (+0.03% 🔺)
import { useLazyQuery } from "dist/react/index.js"	5.7 KB (+0.07% 🔺)
import { useLazyQuery } from "dist/react/index.js" (production)	4.77 KB (+0.03% 🔺)
import { useMutation } from "dist/react/index.js"	3.62 KB (+0.03% 🔺)
import { useMutation } from "dist/react/index.js" (production)	2.84 KB (+0.04% 🔺)
import { useSubscription } from "dist/react/index.js"	4.41 KB (+0.05% 🔺)
import { useSubscription } from "dist/react/index.js" (production)	3.46 KB (0%)
import { useSuspenseQuery } from "dist/react/index.js"	5.49 KB (+0.02% 🔺)
import { useSuspenseQuery } from "dist/react/index.js" (production)	4.15 KB (+0.03% 🔺)
import { useBackgroundQuery } from "dist/react/index.js"	4.99 KB (0%)
import { useBackgroundQuery } from "dist/react/index.js" (production)	3.64 KB (0%)
import { useLoadableQuery } from "dist/react/index.js"	5.07 KB (+0.04% 🔺)
import { useLoadableQuery } from "dist/react/index.js" (production)	3.72 KB (+0.08% 🔺)
import { useReadQuery } from "dist/react/index.js"	3.39 KB (+0.06% 🔺)
import { useReadQuery } from "dist/react/index.js" (production)	3.33 KB (0%)
import { useFragment } from "dist/react/index.js"	2.32 KB (0%)
import { useFragment } from "dist/react/index.js" (production)	2.27 KB (+0.05% 🔺)

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[phryneas]

Suggested change

	if (
	!childChanged &&
	Object.keys(masked).length !== Object.keys(data[keyName]).length
	) {
	childChanged = true;
	}
	childChanged ||= Object.keys(masked).length !== Object.keys(data[keyName]).length;

Just a suggestion, though - whatever you like better :)

[jerelmiller]

I went with your other suggestion. Thanks a bunch!

[phryneas]

Suggested change

	if (childChanged) {
	if (childChanged || Object.keys(masked).length !== Object.keys(data[keyName]).length) {

or maybe this. Both of these should save a bunch of bytes.

[jerelmiller]

Oh ya I like this one a lot. Don't know why I didn't think of this initially 🤦. Great suggestion!

[jerelmiller]

f5b021a