bug: spdx checksum empty array; allow syft to generate SHA1 for spdx-tag-value documents (#1404)

syft/file/digest_cataloger.go

@@ -92,15 +92,11 @@ func DigestsFromFile(closer io.ReadCloser, hashes []crypto.Hash) ([]Digest, erro
 		writers[idx] = hashers[idx]
 	}
 
-	size, err := io.Copy(io.MultiWriter(writers...), closer)
+	_, err := io.Copy(io.MultiWriter(writers...), closer)
 	if err != nil {
 		return nil, err
 	}
 
-	if size == 0 {
-		return make([]Digest, 0), nil
-	}
-
 	result := make([]Digest, len(hashes))
 	// only capture digests when there is content. It is important to do this based on SIZE and not
 	// FILE TYPE. The reasoning is that it is possible for a tar to be crafted with a header-only

syft/file/digest_cataloger_test.go

@@ -29,12 +29,6 @@ func testDigests(t testing.TB, root string, files []string, hashes ...crypto.Has
 			t.Fatalf("could not read %q : %+v", f, err)
 		}
 
-		if len(b) == 0 {
-			// we don't keep digests for empty files
-			digests[source.NewLocation(f).Coordinates] = []Digest{}
-			continue
-		}
-
 		for _, hash := range hashes {
 			h := hash.New()
 			h.Write(b)