The current model reference and the next model reference cannot be equal.

Did you ever figure out the problem? I just ran into it myself and don't see anything obviously wrong. If I figure it out, I'll post again here with my findings.

I just figured it out in my case.

Each of my two 2 VersionedSchemas, V1 and V2, was referring to its static models as [A.self, B.self], which is fine. But I had forgotten that I had also typealiased A and B to the current schema ("typealias A = V1.A"), which was overriding the static references.

I fixed it by referring to the static models within the VersionedSchemas as [Self.A.self, Self.B.self], avoiding confusion with the typealiases.

I came across this while googling and thought I'd also put my solution here for any others it helps:

I was bumping the schema just to use the migrations for ensuring data integrity, and I hadn't actually changed the model. Once I made a change to the model (renamed an attribute I had been meaning to get around to) everything worked fine.

Thanks Guys. The type alias stuff was getting me. I manually put the static declaration with the class in front to avoid my confusion.

Here's my latest VersionedSchema for clarity.

enum ModelSchemaV5: VersionedSchema {
    
    static var versionIdentifier = Schema.Version(5, 0, 0)
    
    static var models: [any PersistentModel.Type] {
        [
            // V1
            ModelSchemaV1.SDAccountingClass.self,
            ModelSchemaV1.SDCacheRecord.self,
            ModelSchemaV1.SDCustomer.self,
            ModelSchemaV1.SDItem.self,
            ModelSchemaV1.SDLocation.self,
            ModelSchemaV1.SDTag.self,
            ModelSchemaV1.SDUOM.self,
            
            // V2
            ModelSchemaV2.SDPurchaseOrder.self,
            ModelSchemaV2.SDPurchaseOrderItem.self,
            ModelSchemaV2.SDVendor.self,
            ModelSchemaV2.SDCarrier.self,
            ModelSchemaV2.SDInventoryLocationSummary.self,
            ModelSchemaV2.SDPurchaseOrderSettings.self,
            
            // V3
            ModelSchemaV3.SDShip.self,
            ModelSchemaV3.SDSalesOrder.self,
            
            // V4
            ModelSchemaV4.SDReceipt.self,
            ModelSchemaV4.SDDocument.self,
            
            // V5
            ModelSchemaV5.SDReceiptItem.self
        ]
    }
}