Enable Alternative Checksum format of algorithm_hash (#526)

* Enable Alternative Checksum format of algorithm-hash

* Adjust alternate delimeter from - to _.

* Update comment with algorithm_hash

Co-authored-by: Sophie Wigmore <sophiemwigmore@gmail.com>

---------

Co-authored-by: Sophie Wigmore <swigmore@vmware.com>
Co-authored-by: Sophie Wigmore <sophiemwigmore@gmail.com>

postal/internal/dependency_mappings.go

@@ -50,6 +50,13 @@ func (d DependencyMappingResolver) FindDependencyMapping(checksum, platformDir s
 				return "", err
 			}
 			return strings.TrimSpace(content), nil
+			// binding provided in the form `algorithm_hash`
+		} else if uri, ok := binding.Entries[strings.Replace(checksum, ":", "_", 1)]; ok {
+			content, err := uri.ReadString()
+			if err != nil {
+				return "", err
+			}
+			return strings.TrimSpace(content), nil
 		}
 	}
 

postal/internal/dependency_mappings_test.go

@@ -55,6 +55,14 @@ func testDependencyMappings(t *testing.T, context spec.G, it spec.S) {
 						"sha512:other-sha": servicebindings.NewEntry(filepath.Join(tmpDir, "entry-data")),
 					},
 				},
+				{
+					Name: "other-binding-with-hyphen",
+					Path: "hypen-another-",
+					Type: "dependency-mapping",
+					Entries: map[string]*servicebindings.Entry{
+						"sha-512_other-sha-underscore": servicebindings.NewEntry(filepath.Join(tmpDir, "entry-data")),
+					},
+				},
 				{
 					Name:    "another-binding",
 					Path:    "another-path",
@@ -85,6 +93,17 @@ func testDependencyMappings(t *testing.T, context spec.G, it spec.S) {
 				})
 			})
 
+			context("the binding is of format <algorithm>_<hash>", func() {
+				it("finds a matching dependency mappings in the platform bindings if there is one", func() {
+					boundDependency, err := resolver.FindDependencyMapping("sha-512:other-sha-underscore", "some-platform-dir")
+					Expect(err).ToNot(HaveOccurred())
+					Expect(bindingResolver.ResolveCall.Receives.Typ).To(Equal("dependency-mapping"))
+					Expect(bindingResolver.ResolveCall.Receives.Provider).To(BeEmpty())
+					Expect(bindingResolver.ResolveCall.Receives.PlatformDir).To(Equal("some-platform-dir"))
+					Expect(boundDependency).To(Equal("dependency-mapping-entry.tgz"))
+				})
+			})
+
 			context("the binding does not contain an algorithm", func() {
 				it("does not find matching dependency mapping when input isn't of sha256 algorithm", func() {
 					boundDependency, err := resolver.FindDependencyMapping("sha512:some-sha", "some-platform-dir")