Cannot clear an optional string (UUID)

[amorenoz]

Say I have:

type bridgeType struct {
	UUID           string            `ovsdb:"_uuid"`
	Name           string            `ovsdb:"name"`
	IPFIX          *string           `ovsdb:"ipfix"`
}

type ipfixType struct {
	UUID    string   `ovsdb:"_uuid"`
	Targets []string `ovsdb:"targets"`
}

As mentioned in #229 , in order to create an IPFIX row, I need to use Update(), so let's do it:

	ipfix := ipfixType{
		UUID:    namedUUID,
		Targets: []string{"127.0.0.1:6650"},
	}
	insertOp, err := client.Create(&ipfix)
        [...]
	bridge := bridgeType{
		UUID:  uuid,
		IPFIX: &namedUUID,
	}
	updateOps, err := client.Where(&bridge).Update(&bridge, &bridge.IPFIX)
	require.NoError(suite.T(), err)

Now, if I want to delete the IPFIX row, I have two options:

1. delete the row itself using Delete()
2. remove the reference to it and let ovsdb-server clean the row for me. I cannot make this one work:

I've tried:

	empty := ""
	bridge.IPFIX = &empty
	updateOps, err = suite.client.Where(&bridge).Update(&bridge, &bridge.IPFIX)

Apart from the code being a bit weird, I get this server-side error:

syntax error: named-uuid string is not a valid <id>

So I also tried

	bridge.IPFIX = nil
	updateOps, err = suite.client.Where(&bridge).Update(&bridge, &bridge.IPFIX)

but I get:

=== RUN   TestOVSIntegrationTestSuite/TestCreateIPFIX                                                                                                                                                                                                                             
    suite.go:63: test panicked: runtime error: invalid memory address or nil pointer dereference                                                                                                                                                                                  
        goroutine 82 [running]:                                                                                                                                                                                                                                                   
        runtime/debug.Stack(0xc000524da8, 0xbe41e0, 0x1044ea0)                                                                           
                /usr/lib/golang/src/runtime/debug/stack.go:24 +0xab                                                                                                                                                                                                               
        github.com/stretchr/testify/suite.failOnPanic(0xc0004c3500)                                                                                                                                                                                                               
                /home/amorenoz/code/go/pkg/mod/github.com/stretchr/[email protected]/suite/suite.go:63 +0x6d                                                                                                                                                                         
        panic(0xbe41e0, 0x1044ea0)                                                                                                                                                                                                                                                
                /usr/lib/golang/src/runtime/panic.go:971 +0x499                                                                                                                                                                                                                   
        github.com/ovn-org/libovsdb/ovsdb.NativeToOvs(0xc000098f00, 0xbae160, 0x0, 0xb8cd01, 0x5, 0x0, 0x0)                                                                                                                                                                       
                /home/amorenoz/code/libovsdb/ovsdb/bindings.go:269 +0x60d                                                                                                                                                                                                         
        github.com/ovn-org/libovsdb/mapper.Mapper.NewRow(0xc0004993e0, 0xc7d6a3, 0x6, 0xba64a0, 0xc00044e360, 0xc00050e4a0, 0x1, 0x1, 0x0, 0x18, ...)                                                                                                                             
                /home/amorenoz/code/libovsdb/mapper/mapper.go:155 +0x63e                                                                                                                                                                                                          
        github.com/ovn-org/libovsdb/client.api.Update(0xc0000a3ae0, 0xd4e110, 0xc0000e2510, 0xba64a0, 0xc00044e360, 0xc00050e4a0, 0x1, 0x1, 0xc00050e4a0, 0xc000508000, ...)                                                                                                      
                /home/amorenoz/code/libovsdb/client/api.go:337 +0x208                                                                                                                                                                                                             
        github.com/ovn-org/libovsdb/test/ovs.(*OVSIntegrationSuite).TestCreateIPFIX(0xc000224900)                                                                                                                                                                                 
                /home/amorenoz/code/libovsdb/test/ovs/ovs_integration_test.go:633 +0xad0                                                 
        reflect.Value.call(0xc0003be360, 0xc0000105a8, 0x13, 0xc7c950, 0x4, 0xc00011de20, 0x1, 0x1, 0xc00018c400, 0xc00018c400, ...)     
                /usr/lib/golang/src/reflect/value.go:476 +0x99c                                                                          
        reflect.Value.Call(0xc0003be360, 0xc0000105a8, 0x13, 0xc00011de20, 0x1, 0x1, 0x26, 0xc00011dc38, 0x48d8b0)                       
                /usr/lib/golang/src/reflect/value.go:337 +0xd9                                                                           
        github.com/stretchr/testify/suite.Run.func1(0xc0004c3500)                                                                        
                /home/amorenoz/code/go/pkg/mod/github.com/stretchr/[email protected]/suite/suite.go:158 +0x392                              
        testing.tRunner(0xc0004c3500, 0xc000408240)                                                                                      
                /usr/lib/golang/src/testing/testing.go:1193 +0x203                                                                       
        created by testing.(*T).Run                                                                                                      
                /usr/lib/golang/src/testing/testing.go:1238 +0x5d8