add CNB path to detect context

Co-authored-by: Daniel Thornton <[email protected]>

build.go

@@ -18,9 +18,9 @@ type BuildContext struct {
 	// buildpack.toml included in the buildpack contents.
 	BuildpackInfo BuildpackInfo
 
-	// CNBPath is the absolute path location of the buildpack contents, eg.
-	// `/layers/io.buildpacks.example`. This path is useful for finding the
-	// buildpack.toml or any other files included in the buildpack.
+	// CNBPath is the absolute path location of the buildpack contents.
+	// This path is useful for finding the buildpack.toml or any other
+	// files included in the buildpack.
 	CNBPath string
 
 	// Layers provides access to layers managed by the buildpack. It can be used

detect.go

@@ -22,6 +22,11 @@ type DetectContext struct {
 	// the lifecycle.
 	WorkingDir string
 
+	// CNBPath is the absolute path location of the buildpack contents.
+	// This path is useful for finding the buildpack.toml or any other
+	// files included in the buildpack.
+	CNBPath string
+
 	// BuildpackInfo includes the details of the buildpack parsed from the
 	// buildpack.toml included in the buildpack contents.
 	BuildpackInfo BuildpackInfo
@@ -117,6 +122,7 @@ func Detect(f DetectFunc, options ...Option) {
 
 	result, err := f(DetectContext{
 		WorkingDir:    dir,
+		CNBPath:       cnbPath,
 		BuildpackInfo: buildpackInfo.Buildpack,
 	})
 	if err != nil {

detect_test.go

@@ -80,6 +80,7 @@ clear-env = false
 
 			Expect(context).To(Equal(packit.DetectContext{
 				WorkingDir: tmpDir,
+				CNBPath:    cnbDir,
 				BuildpackInfo: packit.BuildpackInfo{
 					ID:      "some-id",
 					Name:    "some-name",