repository: Ignore licenses without a name

The Linux kernel has a note about user programs that use the kernel
services by normal system calls. This is part of the COPYING file, but
doesn't provide any value on the actual software license.
go-license-detector recognizes this note, but it doesn't have further
details on it, because it's not a real license.

This change modifies the code so these notes are ignored.

Changelog: fixed
Issue: https://gitlab.com/gitlab-org/gitaly/-/issues/4745

2 files changed, 18 insertions, 12 deletions

diff --git a/internal/gitaly/service/repository/license.go b/internal/gitaly/service/repository/license.go
index 9140af665..c0b12833a 100644
--- a/internal/gitaly/service/repository/license.go
+++ b/internal/gitaly/service/repository/license.go
@@ -104,19 +104,26 @@ func findLicense(ctx context.Context, repo *localrepo.Repo, commitID git.ObjectI
 		return nil, structerr.NewInternal("detect licenses: %w", err)
 	}
 
-	// This should not happen as the error must be returned, but let's keep it safe to avoid panics.
-	if len(detectedLicenses) == 0 {
-		return &gitalypb.FindLicenseResponse{}, nil
-	}
-
 	type bestMatch struct {
 		shortName string
 		api.Match
 	}
 	bestMatches := make([]bestMatch, 0, len(detectedLicenses))
 	for candidate, match := range detectedLicenses {
+		_, err := licensedb.LicenseName(trimDeprecatedPrefix(candidate))
+		if err != nil {
+			if errors.Is(err, licensedb.ErrUnknownLicenseID) {
+				continue
+			}
+			return nil, structerr.NewInternal("license name by id %q: %w", candidate, err)
+		}
 		bestMatches = append(bestMatches, bestMatch{Match: match, shortName: candidate})
 	}
+
+	if len(bestMatches) == 0 {
+		return &gitalypb.FindLicenseResponse{}, nil
+	}
+
 	sort.Slice(bestMatches, func(i, j int) bool {
 		// Because there could be multiple matches with the same confidence, we need
 		// to make sure the function is consistent and returns the same license on
diff --git a/internal/gitaly/service/repository/license_test.go b/internal/gitaly/service/repository/license_test.go
index f7c7b8535..3384d0cad 100644
--- a/internal/gitaly/service/repository/license_test.go
+++ b/internal/gitaly/service/repository/license_test.go
@@ -62,7 +62,6 @@ func testSuccessfulFindLicenseRequest(t *testing.T, cfg config.Cfg, client gital
 			expectedLicenseRuby *gitalypb.FindLicenseResponse
 			expectedLicenseGo   *gitalypb.FindLicenseResponse
 			errorContains       string
-			errorContainsGo     string
 		}{
 			{
 				desc: "repository does not exist",
@@ -128,7 +127,12 @@ func testSuccessfulFindLicenseRequest(t *testing.T, cfg config.Cfg, client gital
 					LicenseNickname:  "LICENSE",
 					LicensePath:      "COPYING",
 				},
-				errorContainsGo: `license name by id "Linux-syscall-note": license id is not known`,
+				expectedLicenseGo: &gitalypb.FindLicenseResponse{
+					LicenseShortName: "gpl-2.0+",
+					LicenseName:      "GNU General Public License v2.0 or later",
+					LicenseUrl:       "https://www.gnu.org/licenses/old-licenses/gpl-2.0-standalone.html",
+					LicensePath:      "COPYING",
+				},
 			},
 			{
 				desc: "unknown license",
@@ -275,11 +279,6 @@ func testSuccessfulFindLicenseRequest(t *testing.T, cfg config.Cfg, client gital
 					require.Contains(t, err.Error(), tc.errorContains)
 					return
 				}
-				if featureflag.GoFindLicense.IsEnabled(ctx) && tc.errorContainsGo != "" {
-					require.Error(t, err)
-					require.Contains(t, err.Error(), tc.errorContainsGo)
-					return
-				}
 
 				require.NoError(t, err)
 				if featureflag.GoFindLicense.IsEnabled(ctx) && tc.expectedLicenseGo != nil {