"GraphQL" Nested Mutations
🛑 NO! ⛔​
"Nested mutations" is the practice of performing side-effects in child fields of the mutation fields. This is explicitly forbidden by the GraphQL spec:
the resolution of fields other than top-level mutation fields must always be side effect-free and idempotent
Therefore, a schema using "nested mutations" is not a GraphQL schema — it does not comply with the GraphQL specification.
There's a number of reasons for this, but the most convincing one for me is that GraphQL is client-focussed and it's important for clients to have a mental model of what the server will do. If the server might perform mutations/side-effects anywhere then the client can't safely cache anything. However, if the client knows that mutations/side-effects only happen in specific locations (currently only in root-level mutation fields) then it can use this knowledge to factor into its caching and re-rendering strategies.
There are some RFCs proposed to address some of the desires behind nested mutations:
The term "nested mutations" has also been used by some people to describe the practice where a single mutation field accepts as input a nested tree of (possibly lists of) input objects which define the mutations to occur. All mutations still happen within this single root-level Mutation field, and thus this pattern is valid GraphQL (and is not the subject of this article).
A better name for this pattern might be "mutation" or "mutation with nested input objects".