[Bug] VPC Config removed on UpdateMode = Full

[djakielski]

I deploy new code and environment variables to an existing Lambda function with an custom VPC config. After a succuessfull deployment, the vpc config is reset to default values (or it removed).

Logfile:

Lambda function existence check:
{FunctionName: myLambdaFunction,}

Lambda function exists:
{Configuration: {FunctionName: myLambdaFunction,FunctionArn: arn:aws:lambda:eu-central-1:xxxxxx:function:myLambdaFunction,Runtime: java8,Role: arn:aws:iam::xxxxx:role/myRole,Handler: myLambdaFunction,CodeSize: 16585710,Description: M2P BasicAuth,Timeout: 45,MemorySize: 512,LastModified: 2020-01-16T16:38:56.216+0000,CodeSha256: PbhzX9CxHlyD8iycLa/KrjGBXe3crg9UEFsoM1SMM7s=,Version: $LATEST,VpcConfig: {SubnetIds: [subnet-0ff9be297563665b3],SecurityGroupIds: [sg-01150928ee3d0d649],VpcId: vpc-0bed89e64fae397f5},Environment: {Variables: {....},},},Code: {RepositoryType: S3,Location: https://awslambda-eu-cent-1-tasks.s3.eu-central-1.amazonaws.com/snapshots/xxxxx/myLambdaFunction-7578507c-c176-4e79-abcd-936dc063a25d?versionId=HMLwUspPr9zVJJFkh1shu5NEiiykJxoX.....}}

Lambda update configuration request:
{FunctionName: myLambdaFunction,VpcConfig: {SubnetIds: [],SecurityGroupIds: []},Environment: {Variables: {.....}},}

Lambda update configuration response:
{FunctionName: myLambdaFunction,FunctionArn: arn:aws:lambda:eu-central-1:xxxx:function:myLambdaFunction,Runtime: java8,Role: arn:aws:iam::xxx:role/MyRole,Handler: myLambdaFunction,CodeSize: 16585710,Description: myLambdaFunction,Timeout: 45,MemorySize: 512,LastModified: 2020-01-16T16:43:48.895+0000,CodeSha256: PbhzX9CxHlyD8iycLa/KrjGBXe3crg9UEFsoM1SMM7s=,Version: $LATEST,VpcConfig: {SubnetIds: [],SecurityGroupIds: [],VpcId: },Environment: {Variables: {......},},}

Lambda update code request:
{FunctionName: myLambdaFunction,ZipFile: java.nio.HeapByteBuffer[pos=0 lim=16585710 cap=16585710],Publish: true}