rover supergraph compose outputs schema in non-deterministic order

[prasek]

Description

Running rover supergraph compose --config ./supergraph.yaml > supergraph.graphql twice against the same inputs results in different outputs, which isn't friendly to version controlling a composed supergraph with git.

For example, when the above command was run on the same inputs, it generated this diff.

Steps to reproduce

Run rover supergraph compose twice against the same inputs and observe different outputs.

Or clone https://github.com/apollographql/supergraph-demo and run make local and see the diff on supergraph.graphql.

Expected result

Running rover supergraph compose twice against the same inputs and should result in the same output.

Actual result

It generated different outputs.

Environment

Run rover info and paste the results here

Rover Info:
Version: 0.0.7
Install Location: /Users/prasek/.rover/bin/rover
OS: Mac OS 11.2.3 [64-bit]
Shell: /bin/zsh

[abernix]

This seems like it could be an upstream bug. It's probably worth tracking here to ensure it's resolved regardless of where the deficiency lie, but the fix will — I suspect — need to land within composeAndValidate (or more likely, usage of implementation details within composeAndValidate).