source: add support for autoinstall data

Since we added a search_drivers checkbox that is uncheckd by default,
there is no longer a way for users to install third-party drivers in an
autoinstall context.

We now implement the autoinstall support for source so that users can
specify what value they want for search_drivers.

Futhermore, to be backward compatible with existing autoinstall
configurations, we now make search_drivers default to true in
autoinstall contexts.

Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>

autoinstall-schema.json

@@ -118,6 +118,17 @@
             ],
             "additionalProperties": false
         },
+        "source": {
+            "type": "object",
+            "properties": {
+                "search_drivers": {
+                    "type": "boolean"
+                }
+            },
+            "required": [
+                "search_drivers"
+            ]
+        },
         "network": {
             "oneOf": [
                 {

subiquity/server/controllers/source.py

@@ -13,7 +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/>.
 
-from typing import Optional
+from typing import Any, Optional
 import os
 
 from curtin.commands.extract import get_handler_for_source
@@ -52,11 +52,41 @@ class SourceController(SubiquityController):
 
     endpoint = API.source
 
+    autoinstall_key = "source"
+    autoinstall_schema = {
+         "type": "object",
+         "properties": {
+             "search_drivers": {
+                 "type": "boolean",
+             },
+         },
+         "required": ["search_drivers"],
+    }
+    # Defaults to true for backward compatibility with existing autoinstall
+    # configurations. Back then, then users were able to install third-party
+    # drivers without this field.
+    autoinstall_default = {"search_drivers": True}
+
     def __init__(self, app):
         super().__init__(app)
         self._handler = None
         self.source_path: Optional[str] = None
 
+    def make_autoinstall(self):
+        return {"search_drivers": self.model.search_drivers}
+
+    def load_autoinstall_data(self, data: Any) -> None:
+        if data is None:
+            # For some reason, the schema validator does not reject
+            # "source: null" despite "type" being "object"
+            data = self.autoinstall_default
+
+        # search_drivers is marked required so the schema validator should
+        # reject any missing data.
+        assert "search_drivers" in data
+
+        self.model.search_drivers = data["search_drivers"]
+
     def start(self):
         path = '/cdrom/casper/install-sources.yaml'
         if self.app.opts.source_catalog is not None: