Wrap selecting boot config function

Author: zliang-akamai

builder/linode/step_create_disk_config.go

@@ -225,6 +225,32 @@ func flattenInstanceConfig(cfg InstanceConfig, diskLabelToID map[string]int) (li
 	return opts, nil
 }
 
+// selectBootConfig determines which configuration profile should be booted.
+// Returns the index of the config to boot, or an error if multiple configs have booted=true.
+// If no configs have booted=true, returns 0 (first config).
+// If one config has booted=true, returns its index.
+func selectBootConfig(configs []InstanceConfig) (int, error) {
+	bootedCount := 0
+	bootedIndex := -1
+
+	for i, cfg := range configs {
+		if cfg.Booted {
+			bootedCount++
+			bootedIndex = i
+		}
+	}
+
+	if bootedCount > 1 {
+		return 0, errors.New("only one configuration profile can have 'booted' set to true")
+	}
+
+	if bootedIndex >= 0 {
+		return bootedIndex, nil
+	}
+
+	return 0, nil
+}
+
 func (s *stepCreateDiskConfig) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {
 	c := state.Get("config").(*Config)
 	ui := state.Get("ui").(packersdk.Ui)
@@ -288,25 +314,10 @@ func (s *stepCreateDiskConfig) Run(ctx context.Context, state multistep.StateBag
 	// Store disk map in state for other steps
 	state.Put("disk_label_to_id", diskLabelToID)
 
-	// Validate that only one config has booted=true
-	bootedCount := 0
-	bootedIndex := -1
-	for i, cfgProfile := range c.InstanceConfigs {
-		if cfgProfile.Booted {
-			bootedCount++
-			bootedIndex = i
-		}
-	}
-
-	if bootedCount > 1 {
-		return handleError("Multiple configuration profiles marked as booted",
-			errors.New("only one configuration profile can have 'booted' set to true"))
-	}
-
-	// Determine which config to boot: the one marked as booted, or the first one
-	bootConfigIndex := 0
-	if bootedIndex >= 0 {
-		bootConfigIndex = bootedIndex
+	// Determine which config to boot
+	bootConfigIndex, err := selectBootConfig(c.InstanceConfigs)
+	if err != nil {
+		return handleError("Multiple configuration profiles marked as booted", err)
 	}
 
 	// Create configuration profiles and track the boot config ID

builder/linode/step_create_disk_config_test.go

@@ -440,3 +440,106 @@ func TestFlattenInstanceConfig(t *testing.T) {
 		})
 	}
 }
+
+// TestSelectBootConfig tests the boot configuration selection logic
+func TestSelectBootConfig(t *testing.T) {
+	tests := []struct {
+		name              string
+		configs           []InstanceConfig
+		wantIndex         int
+		wantError         bool
+		wantErrorContains string
+	}{
+		{
+			name: "Multiple configs with booted=true should error",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: true},
+				{Label: "config2", Booted: true},
+			},
+			wantError:         true,
+			wantErrorContains: "only one configuration profile can have 'booted' set to true",
+		},
+		{
+			name: "Single config with booted=true should use that config",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: false},
+				{Label: "config2", Booted: true},
+				{Label: "config3", Booted: false},
+			},
+			wantIndex: 1,
+			wantError: false,
+		},
+		{
+			name: "No configs with booted=true should default to first config",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: false},
+				{Label: "config2", Booted: false},
+			},
+			wantIndex: 0,
+			wantError: false,
+		},
+		{
+			name: "Single config not marked as booted should use that config",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: false},
+			},
+			wantIndex: 0,
+			wantError: false,
+		},
+		{
+			name: "First config marked as booted should return index 0",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: true},
+				{Label: "config2", Booted: false},
+			},
+			wantIndex: 0,
+			wantError: false,
+		},
+		{
+			name: "Last config marked as booted should return its index",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: false},
+				{Label: "config2", Booted: false},
+				{Label: "config3", Booted: true},
+			},
+			wantIndex: 2,
+			wantError: false,
+		},
+		{
+			name: "Three configs with first one booted",
+			configs: []InstanceConfig{
+				{Label: "config1", Booted: true},
+				{Label: "config2", Booted: false},
+				{Label: "config3", Booted: false},
+			},
+			wantIndex: 0,
+			wantError: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotIndex, err := selectBootConfig(tt.configs)
+
+			if tt.wantError {
+				if err == nil {
+					t.Errorf("selectBootConfig() expected error but got none")
+					return
+				}
+				if tt.wantErrorContains != "" && !strings.Contains(err.Error(), tt.wantErrorContains) {
+					t.Errorf("selectBootConfig() error = %v, want error containing %q", err, tt.wantErrorContains)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("selectBootConfig() unexpected error: %v", err)
+				return
+			}
+
+			if gotIndex != tt.wantIndex {
+				t.Errorf("selectBootConfig() = %d, want %d (config: %q)", gotIndex, tt.wantIndex, tt.configs[tt.wantIndex].Label)
+			}
+		})
+	}
+}