[PATCH] qemu: capabilities: Detect support for JSON args for -netdev

[Peter Krempa]

On Wed, Nov 09, 2022 at 18:18:16 +0100, Peter Krempa wrote:
> JSON args for -netdev were added as precursor for adding the 'dgram'
> network backend type. Enable the detection and update test cases using
> DO_TEST_CAPS_LATEST.
> 
> Enabling the capability also ensures that the -netdev argument is
> validated against the QAPI schema of 'netdev_add' which was already
> implemented but not enabled.
> 
> The parser supporting JSON was added by qemu commit f3eedcddba3 and

https://gitlab.com/qemu-project/qemu/-/commit/f3eedcddba3#28a48d37e50f9c5a429dcaef8c866d9e6b4ad469_1586_1636

You can see that it uses the visitor for 'Netdev' which is the type also
used as argument for 'netdev_add'. Our internals generate a JSON object
for both cases and just convert it to commandline if JSON is not used.

> enabled when adding stream/dgram netdevs in commit 5166fe0ae46.

https://gitlab.com/qemu-project/qemu/-/commit/5166fe0ae46#28a48d37e50f9c5a429dcaef8c866d9e6b4ad469_1628_1642

Here it explicitly detects opening { as modern syntax.