[PATCH pve-manager] fix #7942: pvesh: treat schema without properties as empty object

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

merge_properties() dispatches on the shape of the target schema by
merging into `properties` if present, appending to an `allOf` list, or
wrapping a `oneOf` into a new `allOf`. A schema with none of those
entries died on the assumption that it is not an object.

A lot of endpoints (e.g., /cluster/firewall/options,
/cluster/notifications/matcher-field-values) across our api define the
parameters schema as follows:

    { additionalProperties => 0 }

Before 874d160f317a, pvesh treated this as a valid schema allowing no
parameters. Since that commit, it fails while loading with the
following error:

    unknown schema type (not an object?)

Split the fallback branch into the three cases that can reach it: die
with the offending type if the schema is explicitly not an object, die
with the offending keys if it contains unexpected keys, otherwise treat
`$to` as a valid, empty object and populate `properties` directly.

Fixes: 874d160f317a ("pvesh: support for allOf/oneOf parameter schemas")
Fixes: https://bugzilla.proxmox.com/show_bug.cgi?id=7942
Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
 PVE/CLI/pvesh.pm | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/PVE/CLI/pvesh.pm b/PVE/CLI/pvesh.pm
index 0ff481d4..9568e22b 100755
--- a/PVE/CLI/pvesh.pm
+++ b/PVE/CLI/pvesh.pm
@@ -304,6 +304,12 @@ my $our_properties = {
     },
 };
 
+my sub unknown_schema_keys {
+    my ($schema) = @_;
+
+    return [grep { $_ ne 'additionalProperties' && $_ ne 'type' } keys $schema->%*];
+}
+
 my sub merge_properties {
     my ($from, $to) = @_;
 
@@ -323,7 +329,14 @@ my sub merge_properties {
         my $old = { $to->%* };
         $to->%* = (allOf => [$old, $from]);
     } else {
-        die "unknown schema type (not an object?)\n";
+        die "unknown schema type '$to->{type}' (not an object)\n"
+            if defined($to->{type}) && $to->{type} ne 'object';
+
+        my $unknown = unknown_schema_keys($to);
+        die "unknown schema type, found unexpected keys: " . join(', ', sort($unknown->@*)) . "\n"
+            if $unknown->@*;
+
+        $to->{properties} = { $from->{properties}->%* };
     }
 }
 
-- 
2.47.3