blueprint: fix DiskCustomization.MinSize with existing pattern

pkg/blueprint/disk_customizations.go

@@ -18,6 +18,27 @@ type DiskCustomization struct {
 	Partitions []PartitionCustomization `json:"partitions,omitempty" toml:"partitions,omitempty"`
 }
 
+func (dc *DiskCustomization) UnmarshalJSON(data []byte) error {
+	var dcAnySize struct {
+		MinSize    any                      `json:"minsize,omitempty" toml:"minsize,omitempty"`
+		Partitions []PartitionCustomization `json:"partitions,omitempty" toml:"partitions,omitempty"`
+	}
+	if err := json.Unmarshal(data, &dcAnySize); err != nil {
+		return err
+	}
+
+	dc.Partitions = dcAnySize.Partitions
+
+	if dcAnySize.MinSize != nil {
+		size, err := decodeSize(dcAnySize.MinSize)
+		if err != nil {
+			return err
+		}
+		dc.MinSize = size
+	}
+	return nil
+}
+
 // PartitionCustomization defines a single partition on a disk. The Type
 // defines the kind of "payload" for the partition: plain, lvm, or btrfs.
 //   - plain: the payload will be a filesystem on a partition (e.g. xfs, ext4).

pkg/blueprint/disk_customizations_test.go

@@ -5,10 +5,12 @@ import (
 	"testing"
 
 	"github.com/BurntSushi/toml"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"github.com/osbuild/images/pkg/blueprint"
 	"github.com/osbuild/images/pkg/datasizes"
 	"github.com/osbuild/images/pkg/pathpolicy"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestPartitioningValidation(t *testing.T) {
@@ -1648,3 +1650,51 @@ func TestPartitionCustomizationUnmarshalTOML(t *testing.T) {
 		})
 	}
 }
+
+func TestDiskCustomizationUnmarshalJSON(t *testing.T) {
+	type testCase struct {
+		input    string
+		expected *blueprint.DiskCustomization
+		errorMsg string
+	}
+
+	testCases := map[string]testCase{
+		"nothing": {
+			input: "{}",
+			expected: &blueprint.DiskCustomization{
+				MinSize: 0,
+			},
+		},
+		"minsize/str": {
+			input: `{
+				"minsize": "1234"
+			}`,
+			expected: &blueprint.DiskCustomization{
+				MinSize: 1234,
+			},
+		},
+		"minsize/str-with-unit": {
+			input: `{
+				"minsize": "1 GiB"
+			}`,
+			expected: &blueprint.DiskCustomization{
+				MinSize: 1 * datasizes.GiB,
+			},
+		},
+	}
+
+	for name := range testCases {
+		tc := testCases[name]
+		t.Run(name, func(t *testing.T) {
+			var dc blueprint.DiskCustomization
+
+			err := json.Unmarshal([]byte(tc.input), &dc)
+			if tc.errorMsg == "" {
+				require.NoError(t, err)
+				assert.Equal(t, tc.expected, &dc)
+			} else {
+				assert.EqualError(t, err, tc.errorMsg)
+			}
+		})
+	}
+}