[Feature Request] If No Package is installed and --x-json is specified, vcpkg list should be empty

[pratikpc]

---

Is your feature request related to a problem? Please describe.
A bit of an annoyance
I was writing an app of sorts that more tightly integrates vcpkg and CMake
During that, for obvious reasons, I had to access vcpkg list
So as I was developing an app, I used vcpkg list --x-json

When packages are Installed, output is
{
...blah blah blah
Useful info
}

When nothing is installed
Output is
No packages are installed. Did you mean search?
Proposed solution
Show output as {} (an Empty Object)

Describe alternatives you've considered
On my side, I am checking for an Exception from JSON.parse currently

Additional context
Not really
It's also experimental so unstable behaviour is both fair and expected

Edit:-

Fixing This

The place to fix this would be

vcpkg/toolsrc/src/vcpkg/commands.list.cpp

Line 96 in 2a6442c

if (installed_ipv.empty())

Out here if JSON Mode is enabled, it should output {}

Should I create a PR?

I can help out here

        if (installed_ipv.empty())
        {
            if(args.output_json())
                     System::print2("{}");
            else
                     System::print2("No packages are installed. Did you mean `search`?\n");
            Checks::exit_success(VCPKG_LINE_INFO);
        }

[PhoebeHui]

The original message may be useful for users, however, show output as {} (an Empty Object) also make sense, @strega-nil, could you help confirm this issue?

[strega-nil]

This makes sense to me, although I'd do System::print2(Json::stringify(Json::Object(), {})).

[pratikpc]

Yeah that would be the better method

Sorry

[strega-nil]

Do you want to open a PR?

[pratikpc]

@strega-nil just opened a PR
Thanks for the help!!!