Base Configs Support - Phase 1

toolkit/tools/imagecustomizerapi/config.go

@@ -19,6 +19,7 @@ type Config struct {
 	Scripts         Scripts          `yaml:"scripts" json:"scripts,omitempty"`
 	PreviewFeatures []PreviewFeature `yaml:"previewFeatures" json:"previewFeatures,omitempty"`
 	Output          Output           `yaml:"output" json:"output,omitempty"`
+	BaseConfigs     []BaseConfig     `yaml:"baseConfigs" json:"baseConfigs,omitempty"`
 }
 
 func (c *Config) IsValid() (err error) {
@@ -123,6 +124,18 @@ func (c *Config) IsValid() (err error) {
 		return fmt.Errorf("the 'reinitialize-verity' preview feature must be enabled to use 'storage.reinitializeVerity'")
 	}
 
+	if c.BaseConfigs != nil {
+		if !sliceutils.ContainsValue(c.PreviewFeatures, PreviewFeatureBaseConfigs) {
+			return fmt.Errorf("the '%s' preview feature must be enabled to use 'baseConfigs'", PreviewFeatureBaseConfigs)
+		}
+
+		for i, base := range c.BaseConfigs {
+			if err := base.IsValid(); err != nil {
+				return fmt.Errorf("invalid baseConfig item at index %d:\n%w", i, err)
+			}
+		}
+	}
+
 	return nil
 }
 

toolkit/tools/imagecustomizerapi/previewfeaturetype.go

@@ -28,12 +28,15 @@ const (
 
 	// PreviewFeatureFedora42 enables support for Fedora 42 images.
 	PreviewFeatureFedora42 PreviewFeature = "fedora-42"
+
+	// PreviewFeatureBaseConfigs enables support for base configuration.
+	PreviewFeatureBaseConfigs PreviewFeature = "base-configs"
 )
 
 func (pf PreviewFeature) IsValid() error {
 	switch pf {
 	case PreviewFeatureUki, PreviewFeatureOutputArtifacts, PreviewFeatureInjectFiles, PreviewFeaturePackageSnapshotTime,
-		PreviewFeatureKdumpBootFiles, PreviewFeatureFedora42:
+		PreviewFeatureKdumpBootFiles, PreviewFeatureFedora42, PreviewFeatureBaseConfigs:
 		return nil
 	default:
 		return fmt.Errorf("invalid preview feature: %s", pf)

toolkit/tools/imagecustomizerapi/schema.json

@@ -45,6 +45,15 @@
       "additionalProperties": false,
       "type": "object"
     },
+    "BaseConfig": {
+      "properties": {
+        "path": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object"
+    },
     "BootLoader": {
       "properties": {
         "resetType": {
@@ -82,6 +91,12 @@
         },
         "output": {
           "$ref": "#/$defs/Output"
+        },
+        "baseConfigs": {
+          "items": {
+            "$ref": "#/$defs/BaseConfig"
+          },
+          "type": "array"
         }
       },
       "additionalProperties": false,

toolkit/tools/pkg/imagecustomizerlib/baseconfigs.go

@@ -0,0 +1,127 @@
+package imagecustomizerlib
+
+import (
+	"fmt"
+
+	"path/filepath"
+
+	"github.com/microsoft/azure-linux-image-tools/toolkit/tools/imagecustomizerapi"
+)
+
+func resolveBaseConfigs(cfg *imagecustomizerapi.Config, baseDir string) (*ResolvedConfig, error) {
+	visited := make(map[string]bool)
+	pathStack := []string{}
+
+	configChain, err := BuildInheritanceChain(cfg, baseDir, visited, pathStack)
+	if err != nil {
+		return nil, err
+	}
+
+	resolved := NewResolvedConfig(configChain)
+
+	return resolved, nil
+}
+
+func BuildInheritanceChain(cfg *imagecustomizerapi.Config, baseDir string, visited map[string]bool, pathStack []string) ([]*imagecustomizerapi.Config, error) {
+	if cfg.BaseConfigs != nil {
+		for i, base := range cfg.BaseConfigs {
+			if err := base.IsValid(); err != nil {
+				return nil, fmt.Errorf("invalid baseConfig item at index %d:\n%w", i, err)
+			}
+		}
+	}
+
+	var chain []*imagecustomizerapi.Config
+
+	for _, base := range cfg.BaseConfigs {
+		basePath := filepath.Join(baseDir, base.Path)
+		absPath, err := filepath.Abs(basePath)
+		if err != nil {
+			return nil, err
+		}
+
+		if visited[absPath] {
+			return nil, fmt.Errorf("cycle detected in baseConfigs: %v -> %s", pathStack, absPath)
+		}
+
+		visited[absPath] = true
+		pathStack = append(pathStack, absPath)
+
+		// Load base file into struct
+		var baseCfg imagecustomizerapi.Config
+		if err := imagecustomizerapi.UnmarshalYamlFile(absPath, &baseCfg); err != nil {
+			return nil, fmt.Errorf("failed to load base config %s: %w", absPath, err)
+		}
+
+		// Recurse into base config
+		subChain, err := BuildInheritanceChain(&baseCfg, filepath.Dir(absPath), visited, pathStack)
+		if err != nil {
+			return nil, err
+		}
+
+		chain = append(chain, subChain...)
+	}
+
+	// Add the current config at the end
+	chain = append(chain, cfg)
+
+	return chain, nil
+}
+
+func resolveOverrideFields(chain []*imagecustomizerapi.Config, target *ResolvedConfig) {
+	for _, config := range chain {
+		if config.Input.Image != (imagecustomizerapi.InputImage{}) && config.Input.Image.Path != "" {
+			// .input.image.path
+			target.InputImagePath = config.Input.Image.Path
+		}
+
+		if config.Output != (imagecustomizerapi.Output{}) {
+			// .output.image.path
+			if config.Output.Image != (imagecustomizerapi.OutputImage{}) && config.Output.Image.Path != "" {
+				target.OutputImagePath = config.Output.Image.Path
+			}
+			// .output.image.format
+			if config.Output.Image != (imagecustomizerapi.OutputImage{}) && config.Output.Image.Format != "" {
+				target.OutputImageFormat = config.Output.Image.Format
+			}
+			// .output.image.artifacts.path
+			if config.Output.Artifacts != nil && config.Output.Artifacts.Path != "" {
+				target.OutputArtifactsPath = config.Output.Artifacts.Path
+			}
+		}
+	}
+}
+
+func resolveMergeFields(chain []*imagecustomizerapi.Config, target *ResolvedConfig) {
+	for _, cfg := range chain {
+		// .output.artifacts.items
+		if cfg.Output != (imagecustomizerapi.Output{}) && cfg.Output.Artifacts != nil && len(cfg.Output.Artifacts.Items) > 0 {
+			target.OutputArtifactsItems = mergeOutputArtifactTypes(
+				target.OutputArtifactsItems, cfg.Output.Artifacts.Items,
+			)
+		}
+	}
+}
+
+func mergeOutputArtifactTypes(base, current []imagecustomizerapi.OutputArtifactsItemType) []imagecustomizerapi.OutputArtifactsItemType {
+	seen := make(map[imagecustomizerapi.OutputArtifactsItemType]bool)
+	var merged []imagecustomizerapi.OutputArtifactsItemType
+
+	// Add base items first
+	for _, item := range base {
+		if !seen[item] {
+			merged = append(merged, item)
+			seen[item] = true
+		}
+	}
+
+	// Add current items
+	for _, item := range current {
+		if !seen[item] {
+			merged = append(merged, item)
+			seen[item] = true
+		}
+	}
+
+	return merged
+}

toolkit/tools/pkg/imagecustomizerlib/baseconfigs_test.go

@@ -0,0 +1,98 @@
+package imagecustomizerlib_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/azure-linux-image-tools/toolkit/tools/imagecustomizerapi"
+	"github.com/microsoft/azure-linux-image-tools/toolkit/tools/pkg/imagecustomizerlib"
+)
+
+func TestBaseConfigsInput(t *testing.T) {
+	base := &imagecustomizerapi.Config{
+		Input: imagecustomizerapi.Input{
+			Image: imagecustomizerapi.InputImage{
+				Path: "base-image-1.vhdx",
+			},
+		},
+	}
+
+	current := &imagecustomizerapi.Config{
+		Input: imagecustomizerapi.Input{
+			Image: imagecustomizerapi.InputImage{
+				Path: "base-image-2.vhdx",
+			},
+		},
+	}
+
+	chain := []*imagecustomizerapi.Config{base, current}
+
+	resolved := imagecustomizerlib.NewResolvedConfig(chain)
+
+	if resolved.InputImagePath != "base-image-2.vhdx" {
+		t.Errorf("expected input image path is base-image-2.vhdx, got %s", resolved.InputImagePath)
+	}
+}
+
+func TestBaseConfigsOutput(t *testing.T) {
+	base := &imagecustomizerapi.Config{
+		Output: imagecustomizerapi.Output{
+			Image: imagecustomizerapi.OutputImage{
+				Path: "output-image-1.vhdx",
+			},
+			Artifacts: &imagecustomizerapi.Artifacts{
+				Path: "./artifacts-1",
+				Items: []imagecustomizerapi.OutputArtifactsItemType{
+					imagecustomizerapi.OutputArtifactsItemUkis,
+				},
+			},
+		},
+	}
+
+	current := &imagecustomizerapi.Config{
+		Output: imagecustomizerapi.Output{
+			Image: imagecustomizerapi.OutputImage{
+				Path: "output-image-2.vhdx",
+			},
+			Artifacts: &imagecustomizerapi.Artifacts{
+				Path: "./artifacts-2",
+				Items: []imagecustomizerapi.OutputArtifactsItemType{
+					imagecustomizerapi.OutputArtifactsItemShim,
+				},
+			},
+		},
+	}
+
+	chain := []*imagecustomizerapi.Config{base, current}
+
+	resolved := imagecustomizerlib.NewResolvedConfig(chain)
+
+	if resolved.OutputImagePath != "output-image-2.vhdx" {
+		t.Errorf("expected output path is output-image-2.vhdx, got %s", resolved.OutputImagePath)
+	}
+
+	if resolved.OutputArtifactsPath != "./artifacts-2" {
+		t.Errorf("expected artifacts path is ./artifacts-2, got %s", resolved.OutputArtifactsPath)
+	}
+
+	expectedItems := []imagecustomizerapi.OutputArtifactsItemType{
+		imagecustomizerapi.OutputArtifactsItemUkis,
+		imagecustomizerapi.OutputArtifactsItemShim,
+	}
+	got := resolved.OutputArtifactsItems
+	if len(got) != len(expectedItems) {
+		t.Errorf("expected output artifacts length is %d, got %d", len(expectedItems), len(got))
+	}
+
+	for _, item := range expectedItems {
+		found := false
+		for _, g := range got {
+			if g == item {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("expected artifact item %q not found in result: %v", item, got)
+		}
+	}
+}

toolkit/tools/pkg/imagecustomizerlib/imagecustomizer.go

@@ -144,6 +144,9 @@ type ImageCustomizerParameters struct {
 	osPackages           []OsPackage
 	cosiBootMetadata     *CosiBootloader
 	targetOS             targetos.TargetOs
+
+	// For future migration: fields to be read from resolvedConfig instead of config
+	resolvedConfig *ResolvedConfig
 }
 
 type verityDeviceMetadata struct {
@@ -165,6 +168,18 @@ func createImageCustomizerParameters(ctx context.Context, configPath string, con
 
 	ic := &ImageCustomizerParameters{}
 
+	if len(ic.config.BaseConfigs) > 0 {
+		resolvedConfig, err := resolveBaseConfigs(ic.config, ic.configPath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to load base config:\n%w", err)
+		}
+		ic.config.Input.Image.Path = resolvedConfig.InputImagePath
+		ic.config.Output.Image.Path = resolvedConfig.OutputImagePath
+		ic.config.Output.Image.Format = resolvedConfig.OutputImageFormat
+		ic.config.Output.Artifacts.Path = resolvedConfig.OutputArtifactsPath
+		ic.config.Output.Artifacts.Items = resolvedConfig.OutputArtifactsItems
+	}
+
 	// working directories
 	buildDirAbs, err := filepath.Abs(options.BuildDir)
 	if err != nil {

toolkit/tools/pkg/imagecustomizerlib/resolvedconfig.go

@@ -0,0 +1,27 @@
+package imagecustomizerlib
+
+import (
+	"github.com/microsoft/azure-linux-image-tools/toolkit/tools/imagecustomizerapi"
+)
+
+// ResolvedConfig represents resolved fields and a chain of base configs.
+type ResolvedConfig struct {
+	InputImagePath       string
+	OutputImagePath      string
+	OutputImageFormat    imagecustomizerapi.ImageFormatType
+	OutputArtifactsPath  string
+	OutputArtifactsItems []imagecustomizerapi.OutputArtifactsItemType
+
+	InheritanceChain []*imagecustomizerapi.Config
+}
+
+func NewResolvedConfig(chain []*imagecustomizerapi.Config) *ResolvedConfig {
+	resolved := &ResolvedConfig{
+		InheritanceChain: chain,
+	}
+
+	resolveOverrideFields(chain, resolved)
+	resolveMergeFields(chain, resolved)
+
+	return resolved
+}