Apollo Federation v2.8, v2.9 and v2.10 support

[dariuszkuc]

Product

Hot Chocolate

Is your feature request related to a problem?

HotChocolate currently provides support for Apollo Federation up to version 2.7. It would be great the library could be updated with additional support for Federation v2.8 and v2.9.

Changelog

• Federation v2.8 added support for sharing contextual data between different subgraphs (with ancestor <-> descendant) relationship (docs)
• Federation v2.9 added support for demand control based on the IBM Cost spec (docs)
• Federation v2.10 is all about connectors so there is actually nothing to implement here from the subgraph perspective (its just bumping the fed spec version in the @link import)

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NOTEs:

• Apollo Federation v2.9 @cost directive definition diverges from the IBM Cost spec as instead of supporting arbitrary cost formula, it requires Int value.

The solution you'd like

Built-in support for latest Apollo Federation versions.

[michaelstaib]

I have put it on the backlog for 15.2.

Regarding cost, in Hot Chocolate we have opted for the same restriction. We however added one more thing to the listSize directive which might be a problem. The spec allows for adding additional attributes though. In essence we have added the default list size for when no slicing argument is provided as many users complained about the assumption of a maximum cost in this case.