Introduce struct with metadata to identify a dependency

buildpack.go

@@ -96,6 +96,31 @@ type BuildpackDependency struct {
 	DeprecationDate time.Time `toml:"deprecation_date"`
 }
 
+// DependencyLayerContributorMetadata returns the subset of data from BuildpackDependency that is use as expected metadata for the DependencyLayerContributor.
+type DependencyLayerContributorMetadata struct {
+	// ID is the dependency ID.
+	ID string `toml:"id"`
+
+	// Name is the dependency name.
+	Name string `toml:"name"`
+
+	// Version is the dependency version.
+	Version string `toml:"version"`
+
+	// SHA256 is the hash of the dependency.
+	SHA256 string `toml:"sha256"`
+}
+
+// GetMetadata return the relevant metadata of this dependency
+func (b BuildpackDependency) GetMetadata() DependencyLayerContributorMetadata {
+	return DependencyLayerContributorMetadata{
+		ID:      b.ID,
+		Name:    b.Name,
+		Version: b.Version,
+		SHA256:  b.SHA256,
+	}
+}
+
 // Equals compares the 2 structs if they are equal. This is very simiar to reflect.DeepEqual
 // except that properties that will not work (e.g. DeprecationDate) are ignored.
 func (b1 BuildpackDependency) Equals(b2 BuildpackDependency) bool {

layer.go

@@ -237,7 +237,7 @@ func NewDependencyLayer(dependency BuildpackDependency, cache DependencyCache, t
 func NewDependencyLayerContributor(dependency BuildpackDependency, cache DependencyCache, types libcnb.LayerTypes) DependencyLayerContributor {
 	return DependencyLayerContributor{
 		Dependency:       dependency,
-		ExpectedMetadata: dependency,
+		ExpectedMetadata: dependency.GetMetadata(),
 		DependencyCache:  cache,
 		ExpectedTypes:    types,
 	}