Addreses Issue 11 - PREFIRE download fails on missing hash type check

internal/fetch.go

@@ -34,12 +34,12 @@ func newHash(alg string) (hash.Hash, error) {
 	switch strings.ToLower(alg) {
 	case "md5":
 		hash = md5.New()
-	case "sha256":
+	case "sha256", "sha-256":
 		hash = sha256.New()
-	case "sha512":
+	case "sha512", "sha-512":
 		hash = sha512.New()
 	default:
-		return nil, fmt.Errorf("expected one of md5, sha256, sha512, got %s", alg)
+		return nil, fmt.Errorf("WARNING: expected one of md5, sha256, sha512, got %q", alg)
 	}
 	return hash, nil
 }

internal/fetch_pool.go

@@ -98,10 +98,12 @@ func downloader(
 			defer os.Remove(dest.Name())
 
 			w := &writerHasher{Writer: dest}
+			skipchecksum := false
 			if req.ChecksumAlg != "" {
 				w.hash, err = newHash(req.ChecksumAlg)
 				if err != nil {
-					return err
+					fmt.Println(err)
+					skipchecksum = true
 				}
 			}
 			_, err = fetch(ctx, zult.URL, w)
@@ -114,13 +116,16 @@ func downloader(
 				return fmt.Errorf("probable HTML download content, possibly indicating a bad auth redirect")
 			}
 
-			zult.Checksum = w.Checksum()
+			if !skipchecksum {
+				zult.Checksum = w.Checksum()
+				if zult.Checksum != req.Checksum {
+					return fmt.Errorf("got checksum %s, expected %s", zult.Checksum, req.Checksum)
+				}
+			}
+
 			zult.Size = w.size
 			zult.Duration = time.Since(start)
 
-			if zult.Checksum != req.Checksum {
-				return fmt.Errorf("got checksum %s, expected %s", zult.Checksum, req.Checksum)
-			}
 			if err := os.Rename(dest.Name(), zult.Path); err != nil {
 				return fmt.Errorf("failed to rename %s to %s: %w", dest.Name(), zult.Path, err)
 			}

internal/fetch_test.go

@@ -21,7 +21,7 @@ func TestSplitChecksum(t *testing.T) {
 }
 
 func Test_newHash(t *testing.T) {
-	goodCases := []string{"md5", "MD5", "sha256", "sha512"}
+	goodCases := []string{"md5", "MD5", "sha256", "SHA-256", "sha512", "SHA-512"}
 	for _, test := range goodCases {
 		t.Run(test, func(t *testing.T) {
 			hash, err := newHash(test)