encoding/json: Change of behaviour when decoding json null values into RawMessage

[gsalgado]

1a99ba5 seems to have changed how json null values are decoded into json.RawMessages. After that commit a null value is decoded into an empty byte array whereas before they were decoded into []byte("null"), as can be seen here:

https://play.golang.org/p/m4ubMyAcqL

[dspezia]

Confirmed. This CL has changed the behavior with json.RawMessages.

[dspezia]

The behavior change with json.RawMessage was not intended.

But the documentation says: "The JSON null value unmarshals into an interface, map, pointer, or slice by setting that Go value to nil." A json.RawMessage is a []byte, so setting it to nil (instead of [110 117 108 108]) seems to be in line with the documentation.

I'm not sure the original authors of this package consider a json.RawMessage should always have the same behavior than a []byte though.

[dspezia]

The CL has just been reverted anyway.

[gopherbot]

CL https://golang.org/cl/12893 mentions this issue.

[OttoAllmendinger]

Some of my code has been hit by this bug.

I'm relying on the fact that json.RawMessage decodes to the raw json literal, as explained in the Godoc

[RawMessage] implements Marshaler and Unmarshaler and can be used to delay JSON decoding or precompute a JSON encoding.

If null decodes to []byte(), that is no longer true.