Builder should warn if newer buildpacks write a bom in *.toml

buildpack/bom.go

@@ -0,0 +1,96 @@
+package buildpack
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/buildpacks/lifecycle/api"
+)
+
+type BOMValidator interface {
+	ValidateBOM(GroupBuildpack, []BOMEntry) ([]BOMEntry, error)
+}
+
+func NewBOMValidator(bpAPI string, logger Logger) BOMValidator {
+	switch {
+	case api.MustParse(bpAPI).LessThan("0.5"):
+		return &legacyBOMValidator{}
+	case api.MustParse(bpAPI).LessThan("0.7"):
+		return &v05To06BOMValidator{}
+	default:
+		return &defaultBOMValidator{logger: logger}
+	}
+}
+
+type defaultBOMValidator struct {
+	logger Logger
+}
+
+func (h *defaultBOMValidator) ValidateBOM(bp GroupBuildpack, bom []BOMEntry) ([]BOMEntry, error) {
+	if err := h.validateBOM(bom); err != nil {
+		return []BOMEntry{}, err
+	}
+	return h.processBOM(bp, bom), nil
+}
+
+func (h *defaultBOMValidator) validateBOM(bom []BOMEntry) error {
+	if len(bom) > 0 {
+		h.logger.Warn("BOM table isn't supported in this buildpack api version. The BOM should be written to <layer>.bom.<ext>, launch.bom.<ext>, or build.bom.<ext>.")
+	}
+	return nil
+}
+
+func (h *defaultBOMValidator) processBOM(_ GroupBuildpack, _ []BOMEntry) []BOMEntry {
+	return []BOMEntry{}
+}
+
+type v05To06BOMValidator struct{}
+
+func (h *v05To06BOMValidator) ValidateBOM(bp GroupBuildpack, bom []BOMEntry) ([]BOMEntry, error) {
+	if err := h.validateBOM(bom); err != nil {
+		return []BOMEntry{}, err
+	}
+	return h.processBOM(bp, bom), nil
+}
+
+func (h *v05To06BOMValidator) validateBOM(bom []BOMEntry) error {
+	for _, entry := range bom {
+		if entry.Version != "" {
+			return fmt.Errorf("bom entry '%s' has a top level version which is not allowed. The buildpack should instead set metadata.version", entry.Name)
+		}
+	}
+	return nil
+}
+
+func (h *v05To06BOMValidator) processBOM(buildpack GroupBuildpack, bom []BOMEntry) []BOMEntry {
+	return WithBuildpack(buildpack, bom)
+}
+
+type legacyBOMValidator struct{}
+
+func (h *legacyBOMValidator) ValidateBOM(bp GroupBuildpack, bom []BOMEntry) ([]BOMEntry, error) {
+	if err := h.validateBOM(bom); err != nil {
+		return []BOMEntry{}, err
+	}
+	return h.processBOM(bp, bom), nil
+}
+
+func (h *legacyBOMValidator) validateBOM(bom []BOMEntry) error {
+	for _, entry := range bom {
+		if version, ok := entry.Metadata["version"]; ok {
+			metadataVersion := fmt.Sprintf("%v", version)
+			if entry.Version != "" && entry.Version != metadataVersion {
+				return errors.New("top level version does not match metadata version")
+			}
+		}
+	}
+	return nil
+}
+
+func (h *legacyBOMValidator) processBOM(buildpack GroupBuildpack, bom []BOMEntry) []BOMEntry {
+	bom = WithBuildpack(buildpack, bom)
+	for i := range bom {
+		bom[i].convertVersionToMetadata()
+	}
+	return bom
+}

buildpack/build.go

@@ -249,6 +249,9 @@ func (b *Descriptor) readOutputFiles(bpLayersDir, bpPlanPath string, bpPlanIn Pl
 	var launchTOML LaunchTOML
 	launchPath := filepath.Join(bpLayersDir, "launch.toml")
 
+	bomValidator := NewBOMValidator(b.API, logger)
+
+	var err error
 	if api.MustParse(b.API).LessThan("0.5") {
 		// read buildpack plan
 		var bpPlanOut Plan
@@ -257,13 +260,10 @@ func (b *Descriptor) readOutputFiles(bpLayersDir, bpPlanPath string, bpPlanIn Pl
 		}
 
 		// set BOM and MetRequires
-		if err := validateBOM(bpPlanOut.toBOM(), b.API); err != nil {
+		br.BOM, err = bomValidator.ValidateBOM(bpFromBpInfo, bpPlanOut.toBOM())
+		if err != nil {
 			return BuildResult{}, err
 		}
-		br.BOM = WithBuildpack(bpFromBpInfo, bpPlanOut.toBOM())
-		for i := range br.BOM {
-			br.BOM[i].convertVersionToMetadata()
-		}
 		br.MetRequires = names(bpPlanOut.Entries)
 
 		// read launch.toml, return if not exists
@@ -279,7 +279,7 @@ func (b *Descriptor) readOutputFiles(bpLayersDir, bpPlanPath string, bpPlanIn Pl
 		if _, err := toml.DecodeFile(buildPath, &bpBuild); err != nil && !os.IsNotExist(err) {
 			return BuildResult{}, err
 		}
-		if err := validateBOM(bpBuild.BOM, b.API); err != nil {
+		if _, err := bomValidator.ValidateBOM(bpFromBpInfo, bpBuild.BOM); err != nil {
 			return BuildResult{}, err
 		}
 
@@ -297,10 +297,10 @@ func (b *Descriptor) readOutputFiles(bpLayersDir, bpPlanPath string, bpPlanIn Pl
 		}
 
 		// set BOM
-		if err := validateBOM(launchTOML.BOM, b.API); err != nil {
+		br.BOM, err = bomValidator.ValidateBOM(bpFromBpInfo, launchTOML.BOM)
+		if err != nil {
 			return BuildResult{}, err
 		}
-		br.BOM = WithBuildpack(bpFromBpInfo, launchTOML.BOM)
 	}
 
 	if err := overrideDefaultForOldBuildpacks(launchTOML.Processes, b.API, logger); err != nil {
@@ -352,26 +352,6 @@ func validateNoMultipleDefaults(processes []launch.Process) error {
 	return nil
 }
 
-func validateBOM(bom []BOMEntry, bpAPI string) error {
-	if api.MustParse(bpAPI).LessThan("0.5") {
-		for _, entry := range bom {
-			if version, ok := entry.Metadata["version"]; ok {
-				metadataVersion := fmt.Sprintf("%v", version)
-				if entry.Version != "" && entry.Version != metadataVersion {
-					return errors.New("top level version does not match metadata version")
-				}
-			}
-		}
-	} else {
-		for _, entry := range bom {
-			if entry.Version != "" {
-				return fmt.Errorf("bom entry '%s' has a top level version which is not allowed. The buildpack should instead set metadata.version", entry.Name)
-			}
-		}
-	}
-	return nil
-}
-
 func validateUnmet(unmet []Unmet, bpPlan Plan) error {
 	for _, unmet := range unmet {
 		if unmet.Name == "" {