OPA fmt in OPA 0.58+ improperly stripping assignment and term from chained rules

[grantlanglois]

Short description

OPA 0.58.0, specifically #6323 appears to have introduced what I believe to be a regression in opa fmt where the assignment operator and term in the rule heads of chain rules are removed from the re-written rule head.

Steps To Reproduce

In OPA 0.58+ the OPA fmt'ing the following:

instances_or_clusters[id] = ret {
  instances = input.resources["aws_db_instance"]
  ret = instances[id]
} {
  clusters = input.resources["aws_rds_cluster"]
  ret = clusters[id]
}

Results in the following:

instances_or_clusters[id] = ret if {
	instances = input.resources.aws_db_instance
	ret = instances[id]
}

instances_or_clusters[id] if {
	clusters = input.resources.aws_rds_cluster
	ret = clusters[id]
}

Expected behavior

instances_or_clusters[id] = ret if {
	instances = input.resources.aws_db_instance
	ret = instances[id]
}

instances_or_clusters[id] = ret if {
	clusters = input.resources.aws_rds_cluster
	ret = clusters[id]
}

Additional context

[anderseknert]

Thanks for the bug report, @grantlanglois! That does look like an oversight on my part. I'll take a look.