feat: report unknowns in sbom (#2998)

Signed-off-by: Keith Zantow <kzantow@gmail.com>
Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>
Co-authored-by: Alex Goodman <wagoodman@users.noreply.github.com>

syft/pkg/cataloger/elixir/parse_mix_lock.go

@@ -9,6 +9,7 @@ import (
 	"regexp"
 
 	"github.com/anchore/syft/internal/log"
+	"github.com/anchore/syft/internal/unknown"
 	"github.com/anchore/syft/syft/artifact"
 	"github.com/anchore/syft/syft/file"
 	"github.com/anchore/syft/syft/pkg"
@@ -22,25 +23,33 @@ var mixLockDelimiter = regexp.MustCompile(`[%{}\n" ,:]+`)
 
 // parseMixLock parses a mix.lock and returns the discovered Elixir packages.
 func parseMixLock(_ context.Context, _ file.Resolver, _ *generic.Environment, reader file.LocationReadCloser) ([]pkg.Package, []artifact.Relationship, error) {
+	var errs error
 	r := bufio.NewReader(reader)
 
 	var packages []pkg.Package
+	lineNum := 0
 	for {
+		lineNum++
 		line, err := r.ReadString('\n')
 		switch {
 		case errors.Is(err, io.EOF):
-			return packages, nil, nil
+			if errs == nil {
+				errs = unknown.IfEmptyf(packages, "unable to determine packages")
+			}
+			return packages, nil, errs
 		case err != nil:
 			return nil, nil, fmt.Errorf("failed to parse mix.lock file: %w", err)
 		}
 		tokens := mixLockDelimiter.Split(line, -1)
 		if len(tokens) < 6 {
+			errs = unknown.Appendf(errs, reader, "unable to read mix lock line %d: %s", lineNum, line)
 			continue
 		}
 		name, version, hash, hashExt := tokens[1], tokens[4], tokens[5], tokens[len(tokens)-2]
 
 		if name == "" {
 			log.WithFields("path", reader.RealPath).Debug("skipping empty package name from mix.lock file")
+			errs = unknown.Appendf(errs, reader, "skipping empty package name from mix.lock file, for line: %d: %s", lineNum, line)
 			continue
 		}