Re: A brief look at deprecating our JSON extensions over RFC 8259

[Peter Krempa]

On Mon, Feb 22, 2021 at 18:42:00 +0100, Paolo Bonzini wrote:
> On 22/02/21 15:57, Markus Armbruster wrote:
> > * The block layer's pseudo-protocol "json:" (which can get embedded in
> >    image headers)
> 
> If it gets embedded in image headers, I don't think we'll be able to
> deprecate it ever.  We'd need to keep a converter for old images, at which
> point it's simpler to keep the extensions.

The converter or better 'fixer' actually doesn't need to be able to
interpret the old string, just accept a new. IOW it's more of a
documentation problem, because qemu-img can already do that since it's
able to write invalid JSON without interpreting it:

$ qemu-img rebase -f qcow2 -F qcow2 -b 'json:{' -u /tmp/ble.qcow2
$ qemu-img info /tmp/ble.qcow2
image: /tmp/ble.qcow2
file format: qcow2
virtual size: 10 MiB (10485760 bytes)
disk size: 196 KiB
cluster_size: 65536
backing file: json:{
backing file format: qcow2
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: false
    refcount bits: 16
    corrupt: false