Ensure the generated flathub:: values is compliant

[aleixpol]

According to the spec, is not a thing. is the correct one.

https://freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-custom

Fixes flathub/flathub#4917

[aleixpol]

@barthalion ping

[ximion]

Indeed, metadata was a "proprietary" GNOME extension in ancient times, has never been supported anywhere but in GNOME and isn't even supported there anymore.

Looks like we accidentally resurrected something from the past here.
So +1 from me for this patch :-)

[razzeee]

Emitting both and patching/backporting this in gnome software asap is the only way out. Fortunately it seems quiet simple.

Just should have a followup cleanup issue for some when in the future.

[ximion]

Emitting both and patching/backporting this in gnome software asap is the only way out. Fortunately it seems quiet simple.

That isn't even needed to be fixed in GNOME Software! I just noticed it upgrades "metadata" to "custom" in all versions!
So we could likely even do without that fallback! See https://gitlab.gnome.org/GNOME/gnome-software/-/blob/main/plugins/flatpak/gs-flatpak.c?ref_type=heads#L766

Honestly I think I should do some refactoring in GS so this is less confusing. I think we may actually be able to completely ditch some of that deprecated stuff to make the code more readable.

[barthalion]

Hmm, yeah, I guess I must have implemented it first with <custom>, then realized it's not what appstream-glib does. @razzeee we're going to have to switch backend and frontend to use the new field too at some point.

[ximion]

The good thing is that you don't need to keep the duplicated value, as GNOME Software and appstream-glib will read custom just fine in pretty much any version :-)
So once the website is fixed, this can be greatly simplified.

[razzeee]

Website is likely also fine https://github.com/flathub-infra/website/blob/main/backend/app/utils.py#L216

[ximion]

Website is likely also fine https://github.com/flathub-infra/website/blob/main/backend/app/utils.py#L216

Hmm... A bit OT, but did you know that you could get appstream2dict relatively efficiently via AppStream directly?

import gi
import yaml

gi.require_version('AppStream', '1.0')
from gi.repository import AppStream

def appstream2dict(xml_fname) -> dict[str, dict]:
    mdata = AppStream.Metadata()
    mdata.set_locale('ALL')
    mdata.set_format_style(AppStream.FormatStyle.CATALOG)
    mdata.set_parse_flags(AppStream.ParseFlags.IGNORE_MEDIABASEURL)

    with lzma.open(xml_fname, 'r') as f:
        xml_catalog_data = str(f.read(), 'utf-8')

    mdata.clear_components()
    mdata.parse_data(xml_catalog_data, AppStream.FormatKind.YAML)

    return yaml.safe_load(mdata.components_to_catalog(AppStream.FormatKind.YAML))

You might not want that for various reasons, but it would be dramatically less code ^^