Simple diff for shaded proto messages in Java/Grpc

ProtoDiff.groovy

    // Usage:         diff(Message, OtherMessage).empty 

    def diff(x, y) {
        deepEquals(x.newBuilder().build().getDescriptorForType().fields,
                y.newBuilder().build().getDescriptorForType().fields)
    }

    def deepEquals(List<FieldDescriptor> fields1, List<FieldDescriptor> fields2) {
        if (fields1.size() != fields2.size()) {
            return ["Missing field between ${fields1*.name} and ${fields2*.name}"]
        }

        def errors = []

        fields1.eachWithIndex { field, count ->
            def otherField = fields2.get(count)

            if (field.type != otherField.type) {
                errors.add "Field Type mismatch between ${field.name} and ${otherField.name}"
            }

            if (field.jsonName != otherField.jsonName) {
                errors.add "JsonName mismatch between ${field.name} and ${otherField.name}"
            }

            if (field.type.equals(FieldDescriptor.Type.MESSAGE)) {
                def childError = deepEquals(field.messageType.fields, otherField.messageType.fields)
                if (!childError.empty) {
                    errors.add "Errors found in child message for ${field.name}"
                    errors.addAll(childError)
                }
            }
        }
        return errors
    }