Merge warnings reported for JSONObject custom scalar

[vigie]

Intended outcome:
My understanding is that all scalar values (custom or otherwise) should be treated opaquely and replaced when updating. Such updates should not trigger a data loss merge warning.

Actual outcome:
When merging objects containing fields of custom scalar type JSONObject, merge warning are generated in the console for these fields.

How to reproduce the issue:
Include JSONObject custom scalar into your schema and resolver map and use it in a type definition

scalar JSONObject

type Deployment {
   id: ID!
   state: JSONObject
}

execute a query to fetch an object that uses JSONObject, then update the data in the cache so the merge algorithm runs.

query DeploymentQuery($id: ID) {
    deployment(id: $id)  {
        id
        state
    }
}

Notice that when a deployment object that has a different value for state is being merged, you see warnings in the console about potential data loss for state field.

Versions

  System:
    OS: macOS 10.15.6
  Binaries:
    Node: 12.18.2 - ~/.nvm/versions/node/v12.18.2/bin/node
    npm: 6.14.5 - ~/.nvm/versions/node/v12.18.2/bin/npm
  Browsers:
    Chrome: 85.0.4183.121
    Firefox: 79.0
    Safari: 14.0
  npmPackages:
    @apollo/client: ^3.2.0 => 3.2.0
    apollo-angular: ^2.0.3 => 2.0.4

[benjamn]

@vigie This should be fixed in @apollo/client@3.3.0-beta.5 (which includes #7075).

To be clear, this means you shouldn't need to configure JSONObject scalar fields with merge: false to prevent warnings, because there shouldn't be any warnings when updating scalar fields.

[vigie]

Thanks for the quick response @benjamn, I can confirm the issue appears to be fixed in 3.3.0-beta.5 👍