extend source catalog to be able to define bridge kernel related things

examples/answers/bridge.yaml

@@ -0,0 +1,44 @@
+#source-catalog: examples/sources/bridge.yaml
+Source:
+  source: ubuntu-server
+  search_drivers: true
+Welcome:
+  lang: en_US
+Refresh:
+  update: no
+Keyboard:
+  layout: us
+Zdev:
+  accept-default: yes
+Network:
+  accept-default: yes
+Proxy:
+  proxy: ""
+Mirror:
+  country-code: us
+Filesystem:
+  guided: yes
+  guided-index: 0
+Identity:
+  realname: Ubuntu
+  username: ubuntu
+  hostname: ubuntu-server
+  # ubuntu
+  password: '$6$wdAcoXrU039hKYPd$508Qvbe7ObUnxoj15DRCkzC3qO7edjH0VV7BPNRDYK4QR8ofJaEEF2heacn0QgD.f8pO8SNp83XNdWG6tocBM1'
+SSH:
+  install_server: true
+  pwauth: false
+  authorized_keys:
+    - |
+      ssh-rsa AAAAAAAAAAAAAAAAAAAAAAAAA # ssh-import-id lp:subiquity
+UbuntuPro:
+  token: ""
+SnapList:
+  snaps:
+    hello:
+      channel: stable
+      classic: false
+InstallProgress:
+  reboot: yes
+Drivers:
+  install: no

examples/sources/bridge.yaml

@@ -0,0 +1,28 @@
+version: 1
+sources:
+  - description:
+      en: This version has been customized to have a small runtime footprint in environments
+        where humans are not expected to log in.
+    id: ubuntu-server-minimal
+    locale_support: none
+    name:
+      en: Ubuntu Server (minimized)
+    path: ubuntu-server-minimal.squashfs
+    size: 530485248
+    type: fsimage
+    variant: server
+  - default: true
+    description:
+      en: The default install contains a curated set of packages that provide a comfortable
+        experience for operating your server.
+    id: ubuntu-server
+    locale_support: locale-only
+    name:
+      en: Ubuntu Server
+    path: ubuntu-server-minimal.ubuntu-server.squashfs
+    size: 1066115072
+    type: fsimage-layered
+    variant: server
+bridge_kernel_name: linux-image-brg-22.04
+bridge_kernel_reasons:
+  - nvidia

subiquity/models/source.py

@@ -13,6 +13,7 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import enum
 import logging
 import os
 import typing
@@ -56,6 +57,19 @@ def __attrs_post_init__(self):
             )
 
 
+class BridgeReason(enum.Enum):
+    NVIDIA = "nvidia"
+    ZFS = "zfs"
+
+
+@attr.s(auto_attribs=True, kw_only=True)
+class SourceCatalog:
+    version: int
+    sources: typing.List[CatalogEntry]
+    bridge_kernel_name: typing.Optional[str] = None
+    bridge_kernel_reasons: typing.List[BridgeReason] = attr.Factory(list)
+
+
 legacy_server_entry = CatalogEntry(
     variant="server",
     id="synthesized",
@@ -71,32 +85,39 @@ def __attrs_post_init__(self):
     },
 )
 
+_serializer = Serializer(ignore_unknown_fields=True, serialize_enums_by="value")
+
 
 class SourceModel:
     def __init__(self):
         self._dir = "/cdrom/casper"
         self.current = legacy_server_entry
-        self.sources = [self.current]
+        self.catalog = SourceCatalog(version=1, sources=[self.current])
         self.lang = None
         self.search_drivers = False
 
     def load_from_file(self, fp):
         self._dir = os.path.dirname(fp.name)
         self.sources = []
         self.current = None
-        self.sources = Serializer(ignore_unknown_fields=True).deserialize(
-            typing.List[CatalogEntry], yaml.safe_load(fp)
-        )
-        for entry in self.sources:
+        content = yaml.safe_load(fp)
+        if isinstance(content, list):
+            self.catalog = SourceCatalog(
+                version=1,
+                sources=_serializer.deserialize(typing.List[CatalogEntry], content),
+            )
+        else:
+            self.catalog = _serializer.deserialize(SourceCatalog, content)
+        for entry in self.catalog.sources:
             if entry.default:
                 self.current = entry
-        log.debug("loaded %d sources from %r", len(self.sources), fp.name)
+        log.debug("loaded %d sources from %r", len(self.catalog.sources), fp.name)
         if self.current is None:
-            self.current = self.sources[0]
+            self.current = self.catalog.sources[0]
 
     def get_matching_source(self, id_: str) -> CatalogEntry:
         """Return a source object that has the ID requested."""
-        for source in self.sources:
+        for source in self.catalog.sources:
             if source.id == id_:
                 return source
         raise KeyError

subiquity/server/controllers/source.py

@@ -114,6 +114,8 @@ def start(self):
         self.app.hub.subscribe(
             (InstallerChannels.CONFIGURED, "locale"), self._set_locale
         )
+        if self.model.catalog.version != 1:
+            raise Exception("unknown source catalog version")
 
     def _set_locale(self):
         current = self.app.base_model.locale.selected_language
@@ -128,7 +130,7 @@ async def GET(self) -> SourceSelectionAndSetting:
             search_drivers = True
 
         return SourceSelectionAndSetting(
-            [convert_source(source, cur_lang) for source in self.model.sources],
+            [convert_source(source, cur_lang) for source in self.model.catalog.sources],
             self.model.current.id,
             search_drivers=search_drivers,
         )