Merge pull request #13471 from k8s-infra-cherrypick-robot/cherry-pick-13463-to-release-1.12

[release-1.12] 🐛 Fix upgradePlan computation in GetUpgradePlanFromClusterClassVersions

Author: k8s-ci-robot

exp/topology/desiredstate/upgrade_plan.go

@@ -393,9 +393,19 @@ func GetUpgradePlanFromClusterClassVersions(clusterClassVersions []string) func(
 			}
 		}
 
+		if len(upgradePlan) == 0 {
+			return upgradePlan, nil, nil
+		}
+
 		// In case there is more than one version for one minor, drop all the versions for one minor except the last.
 		simplifiedUpgradePlan := []string{}
 		currentMinor := currentControlPlaneSemVer.Minor
+
+		// Note: Add the current minor version if the upgradePlan only upgrades patch versions.
+		// In this case the `semV.Minor > currentMinor` check below would not add the minor.
+		if currentMinor == desiredSemVer.Minor {
+			simplifiedUpgradePlan = append(simplifiedUpgradePlan, upgradePlan[0])
+		}
 		for _, v := range upgradePlan {
 			semV, err := semver.ParseTolerant(v)
 			if err != nil {

exp/topology/desiredstate/upgrade_plan_test.go

@@ -1054,6 +1054,33 @@ func TestGetUpgradePlanFromClusterClassVersions(t *testing.T) {
 			wantWorkersUpgradePlan:      nil,
 			wantErr:                     false,
 		},
+		{
+			name:                        "upgrade between patch version",
+			clusterClassVersions:        []string{"v1.35.1", "v1.35.2"},
+			desiredVersion:              "v1.35.2",
+			currentControlPlaneVersion:  "v1.35.1",
+			wantControlPlaneUpgradePlan: []string{"v1.35.2"},
+			wantWorkersUpgradePlan:      nil,
+			wantErr:                     false,
+		},
+		{
+			name:                        "upgrade between patch version",
+			clusterClassVersions:        []string{"v1.35.1", "v1.35.2", "v1.35.3"},
+			desiredVersion:              "v1.35.3",
+			currentControlPlaneVersion:  "v1.35.1",
+			wantControlPlaneUpgradePlan: []string{"v1.35.3"},
+			wantWorkersUpgradePlan:      nil,
+			wantErr:                     false,
+		},
+		{
+			name:                        "upgrade between patch version",
+			clusterClassVersions:        []string{"v1.35.1", "v1.35.2", "v1.35.3"},
+			desiredVersion:              "v1.35.2",
+			currentControlPlaneVersion:  "v1.35.1",
+			wantControlPlaneUpgradePlan: []string{"v1.35.2"},
+			wantWorkersUpgradePlan:      nil,
+			wantErr:                     false,
+		},
 		{
 			name:                        "return control plane upgrade plan for more than one minor",
 			clusterClassVersions:        []string{"v1.31.0", "v1.32.0", "v1.33.0"},