Always set CNB_TARGET_* variables during detect, build, and generate

buildpack/build.go

@@ -35,6 +35,7 @@ type BuildInputs struct {
 	LayersDir      string
 	PlatformDir    string
 	Env            BuildEnv
+	TargetEnv      []string
 	Out, Err       io.Writer
 	Plan           Plan
 }
@@ -151,6 +152,9 @@ func runBuildCmd(d BpDescriptor, bpLayersDir, planPath string, inputs BuildInput
 			EnvLayersDir+"="+bpLayersDir,
 		)
 	}
+	if api.MustParse(d.API()).AtLeast("0.10") {
+		cmd.Env = append(cmd.Env, inputs.TargetEnv...)
+	}
 
 	if err = cmd.Run(); err != nil {
 		return NewError(err, ErrTypeBuildpack)

buildpack/detect.go

@@ -30,6 +30,7 @@ type DetectInputs struct {
 	BuildConfigDir string
 	PlatformDir    string
 	Env            BuildEnv
+	TargetEnv      []string
 }
 
 type DetectOutputs struct {
@@ -178,6 +179,9 @@ func runDetect(d detectable, inputs DetectInputs, planPath string, envRootDirKey
 			EnvBuildPlanPath+"="+planPath,
 		)
 	}
+	if api.MustParse(d.API()).AtLeast("0.10") {
+		cmd.Env = append(cmd.Env, inputs.TargetEnv...)
+	}
 
 	if err := cmd.Run(); err != nil {
 		if err, ok := err.(*exec.ExitError); ok {

buildpack/generate.go

@@ -7,6 +7,7 @@ import (
 	"os/exec"
 	"path/filepath"
 
+	"github.com/buildpacks/lifecycle/api"
 	"github.com/buildpacks/lifecycle/internal/extend"
 	"github.com/buildpacks/lifecycle/launch"
 	"github.com/buildpacks/lifecycle/log"
@@ -25,6 +26,7 @@ type GenerateInputs struct {
 	OutputDir      string // a temp directory provided by the lifecycle to capture extensions output
 	PlatformDir    string
 	Env            BuildEnv
+	TargetEnv      []string
 	Out, Err       io.Writer
 	Plan           Plan
 }
@@ -103,6 +105,9 @@ func runGenerateCmd(d ExtDescriptor, extOutputDir, planPath string, inputs Gener
 		EnvOutputDir+"="+extOutputDir,
 		EnvPlatformDir+"="+inputs.PlatformDir,
 	)
+	if api.MustParse(d.API()).AtLeast("0.10") {
+		cmd.Env = append(cmd.Env, inputs.TargetEnv...)
+	}
 
 	if err := cmd.Run(); err != nil {
 		return NewError(err, ErrTypeBuildpack)

env/build.go

@@ -8,11 +8,6 @@ import (
 // BuildEnvIncludelist are env vars that, if set in the lifecycle's execution environment - either in a builder or by the platform, are passed-through to buildpack executables
 var BuildEnvIncludelist = []string{
 	"CNB_STACK_ID", // deprecated as of api 0.12.0
-	"CNB_TARGET_OS",
-	"CNB_TARGET_ARCH",
-	"CNB_TARGET_ARCH_VARIANT",
-	"CNB_TARGET_DISTRO_NAME",
-	"CNB_TARGET_DISTRO_VERSION",
 	"HOSTNAME",
 	"HOME",
 	"HTTPS_PROXY",

env/build_test.go

@@ -35,11 +35,6 @@ func testBuildEnv(t *testing.T, when spec.G, it spec.S) {
 		it("includes expected vars", func() {
 			benv := env.NewBuildEnv([]string{
 				"CNB_STACK_ID=some-stack-id",
-				"CNB_TARGET_ARCH=st-louis",
-				"CNB_TARGET_ARCH_VARIANT=suburban",
-				"CNB_TARGET_OS=BeOS",
-				"CNB_TARGET_DISTRO_NAME=web",
-				"CNB_TARGET_DISTRO_VERSION=3.0",
 				"HOSTNAME=some-hostname",
 				"HOME=some-home",
 				"HTTPS_PROXY=some-https-proxy",
@@ -59,11 +54,6 @@ func testBuildEnv(t *testing.T, when spec.G, it spec.S) {
 			sort.Strings(out)
 			expectedVars := []string{
 				"CNB_STACK_ID=some-stack-id",
-				"CNB_TARGET_ARCH=st-louis",
-				"CNB_TARGET_ARCH_VARIANT=suburban",
-				"CNB_TARGET_DISTRO_NAME=web",
-				"CNB_TARGET_DISTRO_VERSION=3.0",
-				"CNB_TARGET_OS=BeOS",
 				"CPATH=some-cpath",
 				"HOME=some-home",
 				"HOSTNAME=some-hostname",

phase/builder.go

@@ -67,11 +67,6 @@ func (b *Builder) Build() (*files.BuildMetadata, error) {
 	)
 	processMap := newProcessMap()
 	inputs := b.getBuildInputs()
-	if b.AnalyzeMD.RunImage != nil && b.AnalyzeMD.RunImage.TargetMetadata != nil && b.PlatformAPI.AtLeast("0.12") {
-		inputs.Env = env.NewBuildEnv(append(os.Environ(), platform.EnvVarsFor(*b.AnalyzeMD.RunImage.TargetMetadata)...))
-	} else {
-		inputs.Env = env.NewBuildEnv(os.Environ())
-	}
 
 	filteredPlan := b.Plan
 
@@ -153,6 +148,8 @@ func (b *Builder) getBuildInputs() buildpack.BuildInputs {
 		BuildConfigDir: b.BuildConfigDir,
 		LayersDir:      b.LayersDir,
 		PlatformDir:    b.PlatformDir,
+		Env:            env.NewBuildEnv(os.Environ()),
+		TargetEnv:      platform.EnvVarsFor(b.AnalyzeMD.RunImageTarget(), b.Logger),
 		Out:            b.Out,
 		Err:            b.Err,
 	}

phase/detector.go

@@ -238,11 +238,8 @@ func (d *Detector) detectGroup(group buildpack.Group, done []buildpack.GroupElem
 					AppDir:         d.AppDir,
 					BuildConfigDir: d.BuildConfigDir,
 					PlatformDir:    d.PlatformDir,
-				}
-				if d.AnalyzeMD.RunImage != nil && d.AnalyzeMD.RunImage.TargetMetadata != nil && d.PlatformAPI.AtLeast("0.12") {
-					inputs.Env = env.NewBuildEnv(append(os.Environ(), platform.EnvVarsFor(*d.AnalyzeMD.RunImage.TargetMetadata)...))
-				} else {
-					inputs.Env = env.NewBuildEnv(os.Environ())
+					Env:            env.NewBuildEnv(os.Environ()),
+					TargetEnv:      platform.EnvVarsFor(d.AnalyzeMD.RunImageTarget(), d.Logger),
 				}
 				d.Runs.Store(key, d.Executor.Detect(descriptor, inputs, d.Logger)) // this is where we finally invoke bin/detect
 			}

phase/generator.go

@@ -100,9 +100,6 @@ func (g *Generator) Generate() (GenerateResult, error) {
 		g.Logger.Debug("Finding plan")
 		inputs.Plan = filteredPlan.Find(buildpack.KindExtension, ext.ID)
 
-		if g.AnalyzedMD.RunImage != nil && g.AnalyzedMD.RunImage.TargetMetadata != nil && g.PlatformAPI.AtLeast("0.12") {
-			inputs.Env = env.NewBuildEnv(append(inputs.Env.List(), platform.EnvVarsFor(*g.AnalyzedMD.RunImage.TargetMetadata)...))
-		}
 		g.Logger.Debug("Invoking command")
 		result, err := g.Executor.Generate(*descriptor, inputs, g.Logger)
 		if err != nil {
@@ -154,6 +151,7 @@ func (g *Generator) getGenerateInputs() buildpack.GenerateInputs {
 		BuildConfigDir: g.BuildConfigDir,
 		PlatformDir:    g.PlatformDir,
 		Env:            env.NewBuildEnv(os.Environ()),
+		TargetEnv:      platform.EnvVarsFor(g.AnalyzedMD.RunImageTarget(), g.Logger),
 		Out:            g.Out,
 		Err:            g.Err,
 	}

platform/run_image_test.go

@@ -204,7 +204,7 @@ func testRunImage(t *testing.T, when spec.G, it spec.S) {
 	when(".EnvVarsFor", func() {
 		it("returns the right thing", func() {
 			tm := files.TargetMetadata{Arch: "pentium", ArchVariant: "mmx", ID: "my-id", OS: "linux", Distro: &files.OSDistro{Name: "nix", Version: "22.11"}}
-			observed := platform.EnvVarsFor(tm)
+			observed := platform.EnvVarsFor(tm, nil)
 			h.AssertContains(t, observed, "CNB_TARGET_ARCH="+tm.Arch)
 			h.AssertContains(t, observed, "CNB_TARGET_ARCH_VARIANT="+tm.ArchVariant)
 			h.AssertContains(t, observed, "CNB_TARGET_DISTRO_NAME="+tm.Distro.Name)
@@ -215,7 +215,7 @@ func testRunImage(t *testing.T, when spec.G, it spec.S) {
 
 		it("does not return the wrong thing", func() {
 			tm := files.TargetMetadata{Arch: "pentium", OS: "linux"}
-			observed := platform.EnvVarsFor(tm)
+			observed := platform.EnvVarsFor(tm, nil)
 			h.AssertContains(t, observed, "CNB_TARGET_ARCH="+tm.Arch)
 			h.AssertContains(t, observed, "CNB_TARGET_OS="+tm.OS)
 			// note: per the spec only the ID field is optional, so I guess the others should always be set: https://github.com/buildpacks/rfcs/blob/main/text/0096-remove-stacks-mixins.md#runtime-metadata

platform/target_data.go

@@ -9,11 +9,19 @@ import (
 	"github.com/buildpacks/lifecycle/platform/files"
 )
 
-// Fulfills the prophecy set forth in https://github.com/buildpacks/rfcs/blob/b8abe33f2bdc58792acf0bd094dc4ce3c8a54dbb/text/0096-remove-stacks-mixins.md?plain=1#L97
+// EnvVarsFor fulfills the prophecy set forth in https://github.com/buildpacks/rfcs/blob/b8abe33f2bdc58792acf0bd094dc4ce3c8a54dbb/text/0096-remove-stacks-mixins.md?plain=1#L97
 // by returning an array of "VARIABLE=value" strings suitable for inclusion in your environment or complete breakfast.
-func EnvVarsFor(tm files.TargetMetadata) []string {
-	ret := []string{"CNB_TARGET_OS=" + tm.OS, "CNB_TARGET_ARCH=" + tm.Arch}
-	ret = append(ret, "CNB_TARGET_ARCH_VARIANT="+tm.ArchVariant)
+func EnvVarsFor(tm files.TargetMetadata, logger log.Logger) []string {
+	// we should always have os & arch,
+	// if they are not populated try to get target information from the build-time base image
+	if tm.OS == "" {
+		GetTargetOSFromFileSystem(&fsutil.Detect{}, &tm, logger)
+	}
+	ret := []string{
+		"CNB_TARGET_OS=" + tm.OS,
+		"CNB_TARGET_ARCH=" + tm.Arch,
+		"CNB_TARGET_ARCH_VARIANT=" + tm.ArchVariant,
+	}
 	var distName, distVersion string
 	if tm.Distro != nil {
 		distName = tm.Distro.Name