install/aleph: skip serializing optional fields if None

This avoids writing out fields with `null` values. See
coreos/bootupd#1166.

Signed-off-by: Rolv Apneseth <rolv.apneseth@gmail.com>

Author: Rolv-Apneseth

crates/lib/src/install/aleph.rs

@@ -31,8 +31,10 @@ pub(crate) struct InstallAleph {
     #[serde(skip_serializing_if = "BTreeMap::is_empty")]
     pub(crate) labels: BTreeMap<String, String>,
     /// The version number
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) version: Option<String>,
     /// The timestamp
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) timestamp: Option<chrono::DateTime<chrono::Utc>>,
     /// The `uname -r` of the kernel doing the installation
     pub(crate) kernel: String,

tmt/tests/booted/readonly/013-test-aleph.nu

@@ -71,6 +71,24 @@ if $is_composefs {
         let bootc_label = $labels | get "containers.bootc"
         assert ($bootc_label | is-not-empty) "containers.bootc label should be present"
     }
+
+    # The version field is optional (skip_serializing_if = Option::is_none),
+    # but if present it should match the booted image's version.
+    let version = $aleph.version? | default null
+    if $version != null {
+        assert ($version | is-not-empty) "version field, if present, should be non-empty"
+        let booted_version = $booted.image.version
+        assert equal $version $booted_version "version should match the booted image's version"
+    }
+
+    # The timestamp field may be absent if empty (skip_serializing_if), but if
+    # present it should match the booted image's timestamp.
+    let timestamp = $aleph.timestamp? | default null
+    if $timestamp != null {
+        assert ($timestamp | is-not-empty) "timestamp field, if present, should be non-empty"
+        let booted_timestamp = $booted.image.timestamp
+        assert equal $timestamp $booted_timestamp "timestamp should match the booted image's timestamp"
+    }
 }
 
 tap ok