Similar issue, using graphql-tag/loader with with a literal importing a fragment like this results in a required-fields error if requiredFields: ['id']:

#import "./MessageFragment.graphql"

mutation createMessage($input: MessageInput!) {
  createMessage(input: $input) {
    ...MessageFragment
  }
} 

fragment MessageFragment on Message {
  id
  snippedOtherFields
}

Seems like it is the intended behaviour if I understand this comment properly:

I don't completely understand the comment, though. What does it mean for a fragment to cover all of the possible type options?

I guess when you have something like this in your fragment:

... on FirstType {
  id
}

But the parent supports:

... on FirstType {
  id
}

... on SecondType {
  id
}

or

parent {
  id
  ... on FirstType {
	...
  }

  ... on SecondType {
    ...
  }
}

At least this is how I understand it.

I suppose a decision was taken not to implement checking fragments exhaustively to see if they include a required field.

Yeah I guess so, not sure how hard it would be to implement that though

It seems like field selection merging is part of the GraphQL specification: https://graphql.github.io/graphql-spec/draft/#sec-Field-Selection-Merging

So this is not really a bug per se but more a feature request to be more exhaustive in checking for the inclusion of required fiels in fragments.