Adjust behavior of noarch PURLs

If a PURL does not have an arch= key, then we will assume it applies to any arch. This would be for JAR files or other non-architecture dependent packages. This behavior is slightly different than when there is no PURL at all. If there is no PURL at all, then we assume x86. This is for backwards compatibility, for buildpacks that do not include PURLs.

Signed-off-by: Daniel Mikusa <[email protected]>

buildpack.go

@@ -560,7 +560,7 @@ func archFromPURL(rawPURL string) (string, error) {
 		return arch[0], nil
 	}
 
-	return "amd64", nil
+	return archFromSystem(), nil
 }
 
 func archFromSystem() string {

buildpack_test.go

@@ -355,6 +355,33 @@ func testBuildpack(t *testing.T, context spec.G, it spec.S) {
 				}))
 			})
 
+			it("filters by arch where arch should match any", func() {
+				resolver.Dependencies = []libpak.BuildpackDependency{
+					{
+						ID:      "test-id-1",
+						Name:    "test-name",
+						Version: "1.0",
+						URI:     "test-uri",
+						SHA256:  "test-sha256",
+						Stacks:  []string{"test-stack-1", "test-stack-2"},
+						PURL:    "pkg:generic/[email protected]",
+					},
+				}
+				resolver.StackID = "test-stack-1"
+
+				t.Setenv("BP_ARCH", "arm64")
+
+				Expect(resolver.Resolve("test-id-1", "1.0")).To(Equal(libpak.BuildpackDependency{
+					ID:      "test-id-1",
+					Name:    "test-name",
+					Version: "1.0",
+					URI:     "test-uri",
+					SHA256:  "test-sha256",
+					Stacks:  []string{"test-stack-1", "test-stack-2"},
+					PURL:    "pkg:generic/[email protected]",
+				}))
+			})
+
 			it("filters by version constraint", func() {
 				resolver.Dependencies = []libpak.BuildpackDependency{
 					{