MarshalJson is missing fields for InterfacePropertiesFormat

[MirzaSikander]

Bug Report

• import path of package in question, e.g. .../services/compute/mgmt/2018-06-01/compute
/Azure/azure-sdk-for-go/services/network/mgmt/2020-07-01/network/
• SDK version e.g. master, latest, 18.1.0
  v50.1.0
• output of go version
go version go1.15.6 linux/amd64

• What happened?
  Breaking change.
  In the API version 2020-07-01, InterfacePropertiesFormat and its MarshalJSON looks like this:

// InterfacePropertiesFormat networkInterface properties.
type InterfacePropertiesFormat struct {
	// VirtualMachine - READ-ONLY; The reference to a virtual machine.
	VirtualMachine *SubResource `json:"virtualMachine,omitempty"`
	// NetworkSecurityGroup - The reference to the NetworkSecurityGroup resource.
	NetworkSecurityGroup *SecurityGroup `json:"networkSecurityGroup,omitempty"`
	// PrivateEndpoint - READ-ONLY; A reference to the private endpoint to which the network interface is linked.
	PrivateEndpoint *PrivateEndpoint `json:"privateEndpoint,omitempty"`
	// IPConfigurations - A list of IPConfigurations of the network interface.
	IPConfigurations *[]InterfaceIPConfiguration `json:"ipConfigurations,omitempty"`
	// TapConfigurations - READ-ONLY; A list of TapConfigurations of the network interface.
	TapConfigurations *[]InterfaceTapConfiguration `json:"tapConfigurations,omitempty"`
	// DNSSettings - The DNS settings in network interface.
	DNSSettings *InterfaceDNSSettings `json:"dnsSettings,omitempty"`
	// MacAddress - READ-ONLY; The MAC address of the network interface.
	MacAddress *string `json:"macAddress,omitempty"`
	// Primary - READ-ONLY; Whether this is a primary network interface on a virtual machine.
	Primary *bool `json:"primary,omitempty"`
	// EnableAcceleratedNetworking - If the network interface is accelerated networking enabled.
	EnableAcceleratedNetworking *bool `json:"enableAcceleratedNetworking,omitempty"`
	// EnableIPForwarding - Indicates whether IP forwarding is enabled on this network interface.
	EnableIPForwarding *bool `json:"enableIPForwarding,omitempty"`
	// HostedWorkloads - READ-ONLY; A list of references to linked BareMetal resources.
	HostedWorkloads *[]string `json:"hostedWorkloads,omitempty"`
	// DscpConfiguration - READ-ONLY; A reference to the dscp configuration to which the network interface is linked.
	DscpConfiguration *SubResource `json:"dscpConfiguration,omitempty"`
	// ResourceGUID - READ-ONLY; The resource GUID property of the network interface resource.
	ResourceGUID *string `json:"resourceGuid,omitempty"`
	// ProvisioningState - READ-ONLY; The provisioning state of the network interface resource. Possible values include: 'Succeeded', 'Updating', 'Deleting', 'Failed'
	ProvisioningState ProvisioningState `json:"provisioningState,omitempty"`
}

// MarshalJSON is the custom marshaler for InterfacePropertiesFormat.
func (ipf InterfacePropertiesFormat) MarshalJSON() ([]byte, error) {
	objectMap := make(map[string]interface{})
	if ipf.NetworkSecurityGroup != nil {
		objectMap["networkSecurityGroup"] = ipf.NetworkSecurityGroup
	}
	if ipf.IPConfigurations != nil {
		objectMap["ipConfigurations"] = ipf.IPConfigurations
	}
	if ipf.DNSSettings != nil {
		objectMap["dnsSettings"] = ipf.DNSSettings
	}
	if ipf.EnableAcceleratedNetworking != nil {
		objectMap["enableAcceleratedNetworking"] = ipf.EnableAcceleratedNetworking
	}
	if ipf.EnableIPForwarding != nil {
		objectMap["enableIPForwarding"] = ipf.EnableIPForwarding
	}
	return json.Marshal(objectMap)
}

https://raw.githubusercontent.com/Azure/azure-sdk-for-go/master/services/network/mgmt/2020-07-01/network/models.go

If you look at an older API version such as 2019-06-01, you will notice that the MarshalJSON for InterfacePropertiesFormat has a lot more fields that are being marshalled.

// MarshalJSON is the custom marshaler for InterfacePropertiesFormat.
func (ipf InterfacePropertiesFormat) MarshalJSON() ([]byte, error) {
	objectMap := make(map[string]interface{})
	if ipf.NetworkSecurityGroup != nil {
		objectMap["networkSecurityGroup"] = ipf.NetworkSecurityGroup
	}
	if ipf.IPConfigurations != nil {
		objectMap["ipConfigurations"] = ipf.IPConfigurations
	}
	if ipf.TapConfigurations != nil {
		objectMap["tapConfigurations"] = ipf.TapConfigurations
	}
	if ipf.DNSSettings != nil {
		objectMap["dnsSettings"] = ipf.DNSSettings
	}
	if ipf.MacAddress != nil {
		objectMap["macAddress"] = ipf.MacAddress
	}
	if ipf.Primary != nil {
		objectMap["primary"] = ipf.Primary
	}
	if ipf.EnableAcceleratedNetworking != nil {
		objectMap["enableAcceleratedNetworking"] = ipf.EnableAcceleratedNetworking
	}
	if ipf.EnableIPForwarding != nil {
		objectMap["enableIPForwarding"] = ipf.EnableIPForwarding
	}
	if ipf.ResourceGUID != nil {
		objectMap["resourceGuid"] = ipf.ResourceGUID
	}
	if ipf.ProvisioningState != nil {
		objectMap["provisioningState"] = ipf.ProvisioningState
	}
	return json.Marshal(objectMap)
}

https://raw.githubusercontent.com/Azure/azure-sdk-for-go/master/services/network/mgmt/2019-06-01/network/models.go

• What did you expect or want to happen?
  Looking at the swagger spec, nothing stands out so it is strange that these fields were left out.
  https://github.com/Azure/azure-rest-api-specs/blob/d70b7cc88d45ef55484c26251f4d5497f12b5dad/specification/network/resource-manager/Microsoft.Network/stable/2020-07-01/networkInterface.json#L1160

Is this by design?

[ArcturusZhang]

Hi @MirzaSikander thanks for this issue.

Unfortunately I have to say this is by design. Internally the SDK relies on the marshalling functionality to transform a go SDK struct into the JSON body in a REST API request in which we cannot have the readOnly properties. Therefore you might notice those missing parts in the marshaller all correspond to a read only property (you could find the read only note in the comment of that property).

We have received an issue discussing about this problem which is more general, and we are planning to do something to improve this, please stay tuned.
In the meantime, I will close this issue in favor of #12227