InMemoryCache is deep freezing results

Intended outcome:

Data can be mutated (not ideal, but some 3rd party libs rely on being able to mutate objects).

It would nice if there was a flag to disable object freezing.

Actual outcome:

TypeError: Cannot add property X, object is not extensible

How to reproduce the issue:

new ApolloClient({
  cache: new InMemoryCache(),
  link: new HttpLink({ uri: process.env.REACT_APP_GRAPHQL_URL }),
})

const { loading, data, error } = useQuery<Query>(QUERY);
data.result.X = '';

Versions

  System:
    OS: macOS 10.15.3
  Binaries:
    Node: 12.14.0
    Yarn: 1.22.0
    npm: 6.13.4
  Browsers:
    Chrome: 80.0.3987.116
    Safari: 13.0.5
  npmPackages:
    @apollo/client: ^3.0.0-beta.37 => 3.0.0-beta.37 
    @apollo/link-context: ^2.0.0-beta.3 => 2.0.0-beta.3 
    apollo: ^2.23.0 => 2.23.0

[benjamn]

See https://github.com/apollographql/apollo-client/pull/5153.

If you have to provide mutable data to external libs, you should deep-clone it first. Even just JSON.parse(JSON.stringify(data)) will work here, since GraphQL response data is inherently JSON-serializable.

The freezing is necessary because cache results can be shared between multiple consumers, so letting one of them modify the result is unacceptable.

Also, the freezing happens only in development, so it has no production performance penalty, in case you were concerned about that.

[narciero]

@dylanwulf Yea but it seems the freezeResults flag was removed from the InMemoryCache ctor?

From the article:

In Apollo Client 3.0, we intend to make both freezeResults and assumeImmutableResults true by default

const client = new ApolloClient({
  link: ...,
  cache: new InMemoryCache({
    freezeResults: true,
  }),
  assumeImmutableResults: true,
});