Fix assertion errors when querying types with no common supertypes at… #2467
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… the same path
Fetches input selections used to be based on the queried subgraph
schema. However, those selections truly applies to the in-memory data
maintained by the gateway/router, so the supergraph. This used to
not matter (all input selection did correctly applied to the subgraph
schema), but `@interfaceObject` made it so that some input selections
could be invalid for the subgraph. Typically, a fetch that queries a
subgraph with an `@interfaceObject` may look like:
```
Fetch(service: 'A') {
{
... on Book {
id
}
} => {
... on Product {
<some fields>
}
}
}
```
where `Book` is a concrete implementation of `Product` but unknown to
subgraph `A`.
However, basing the input selections on the supergraph schema means
having the parent type, in the supergraph, for those selections, and
because some fetches can query multiple different entities, this is
not trivial.
The initial code for `@interfaceObject` make the (incorrect) assumption
that, when a fetch does query multiple types, then we could always find
a common supertype for all those types, and so was using that type as
parent type.
Unfortunately, this isn't always true (see test in this PR, which uses
a union type with types having a field with the same name but different
(and unrelated) types).
So in pratice, fetch inputs cannot always have a common parent type.
This patch thus changes the fetch inputs to be a map of type to
selection sets instead of a single selection set.
Note that it does mean that the `requires` field of a `FetchGroup` is
not a true valid "single" selection for the supergraph (or any subgraph
for that matter), but it is more of a "fun fact" since the execution
never relied on this anyway.
Fixes apollographql#2466
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trevor-scheer
approved these changes
Mar 15, 2023
This was referenced Mar 15, 2023
pcmanus
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May 16, 2023
… the same path (#2467) Fetches input selections used to be based on the queried subgraph schema. However, those selections truly applies to the in-memory data maintained by the gateway/router, so the supergraph. This used to not matter (all input selection did correctly applied to the subgraph schema), but `@interfaceObject` made it so that some input selections could be invalid for the subgraph. Typically, a fetch that queries a subgraph with an `@interfaceObject` may look like: ``` Fetch(service: 'A') { { ... on Book { id } } => { ... on Product { <some fields> } } } ``` where `Book` is a concrete implementation of `Product` but unknown to subgraph `A`. However, basing the input selections on the supergraph schema means having the parent type, in the supergraph, for those selections, and because some fetches can query multiple different entities, this is not trivial. The initial code for `@interfaceObject` make the (incorrect) assumption that, when a fetch does query multiple types, then we could always find a common supertype for all those types, and so was using that type as parent type. Unfortunately, this isn't always true (see test in this PR, which uses a union type with types having a field with the same name but different (and unrelated) types). So in pratice, fetch inputs cannot always have a common parent type. This patch thus changes the fetch inputs to be a map of type to selection sets instead of a single selection set. Note that it does mean that the `requires` field of a `FetchGroup` is not a true valid "single" selection for the supergraph (or any subgraph for that matter), but it is more of a "fun fact" since the execution never relied on this anyway. Fixes #2466
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… the same path
Fetches input selections used to be based on the queried subgraph schema. However, those selections truly applies to the in-memory data maintained by the gateway/router, so the supergraph. This used to not matter (all input selection did correctly applied to the subgraph schema), but
@interfaceObjectmade it so that some input selections could be invalid for the subgraph. Typically, a fetch that queries a subgraph with an@interfaceObjectmay look like:where
Bookis a concrete implementation ofProductbut unknown to subgraphA.However, basing the input selections on the supergraph schema means having the parent type, in the supergraph, for those selections, and because some fetches can query multiple different entities, this is not trivial.
The initial code for
@interfaceObjectmake the (incorrect) assumption that, when a fetch does query multiple types, then we could always find a common supertype for all those types, and so was using that type as parent type.Unfortunately, this isn't always true (see test in this PR, which uses a union type with types having a field with the same name but different (and unrelated) types).
So in pratice, fetch inputs cannot always have a common parent type. This patch thus changes the fetch inputs to be a map of type to selection sets instead of a single selection set.
Note that it does mean that the
requiresfield of aFetchGroupis not a true valid "single" selection for the supergraph (or any subgraph for that matter), but it is more of a "fun fact" since the execution never relied on this anyway.Fixes #2466