Hide fields from public federated gateway

[movio]

Hide fields from public federated gateway

[nmaquet]

This could be easily achieved by writing a Bramble plugin. The 'Init()' method on each plugin receives the schema so you can apply filtering rules and modify the schema in place that way. Happy to guide you through this if you want to contribute a PR.

[hsblhsn]

Can you give me an hit about how to hide a field in with the Init method by putting a directive (ex: @internal) in my service's schema?

I tried few times, but couldn't get it to work yet. A little workable hint may help me get it.

Thank you @nmaquet!

[nmaquet]

I've had a closer look and unfortunately modifying the schema in the Init() function isn't sufficient since the schema is rebuilt regularly. I think the only way to achieve this would be to add a new plugin method, something like AfterSchemaUpdate(schema *ast.Schema) where the BasePlugin implementation just does a no-op. To make this new plugin method work, you'll need to modify UpdateSchema on ExecutableSchema to call each plugin's AfterSchemaUpdate method after the schema is updated (before the mutex Unlock()).

Here's what the AfterSchemaUpdate method could look like:

func (p *HidingPlugin) AfterSchemaUpate(schema *ast.Schema) {
	if schema.Query != nil {
		schema.Query.Fields = p.filterFieldList(schema.Query.Fields)
	}
	if schema.Mutation != nil {
		schema.Mutation.Fields = p.filterFieldList(schema.Mutation.Fields)
	}
	if schema.Subscription != nil {
		schema.Subscription.Fields = p.filterFieldList(schema.Subscription.Fields)
	}
	for _, t := range schema.Types {
		t.Fields = p.filterFieldList(t.Fields)
	}
	for _, ts := range schema.PossibleTypes {
		for _, t := range ts {
			t.Fields = p.filterFieldList(t.Fields)
		}
	}
	for _, ts := range schema.Implements {
		for _, t := range ts {
			t.Fields = p.filterFieldList(t.Fields)
		}
	}
}

func (p *HidingPlugin) filterFieldList(fields ast.FieldList) ast.FieldList {
	result := ast.FieldList{}
	for _, field := range fields {
		if field.Directives.ForName("hidden") == nil {
			result = append(result, field)
		}
	}
	return result
}

[nmaquet]

An additional difficulty that I've forgotten to mention is that Bramble discards directives it doesn't know about. See https://github.com/movio/bramble/blob/main/merge.go#L226
If you want to keep your hidden directive in the merged schema (required to do filtering) you'll have to either add the hidden directive to the allowable directives in an hardcoded fashion (wouldn't be suitable for a PR unfortunately) or extend the plugin API to allow overriding the allowable directives list.

[hsblhsn]

Can we add a new feature called scoped endpoint?

extend type Mutation {
    blockUser(id: ID!) @boundary("/internal")
    banUser(id: ID!) @boundary("/internal")
    anotherMutation(id: ID!)
}

When, running the gateway, http://example.com/internal will resolve all the queries,type,mutations loaded with @boundary("/internal") directive?
Any other fields, queries, mutations will be available on http://example.com/query.

What do you think? If it seems good, I can open another issue for this and close this one.

[nmaquet]

Hey @hsblhsn the change you're proposing is too big and not something we're interested in at this time. We're trying to keep Bramble simple and small and do one thing well. We're happy to consider extending Bramble's plugin API to accommodate more use cases, but we won't change the federation spec unless absolutely necessary. Closing this for now, let us know if you want to revisit a plugin-based approach as described above.