fix(sourceanalysis): return an error instead of exiting when an rlib has no object file

internal/sourceanalysis/rust.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"log"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -193,8 +192,11 @@ func extractRlibArchive(rlibPath string) (bytes.Buffer, error) {
 	}
 	for {
 		header, err := reader.Next()
+		if errors.Is(err, io.EOF) {
+			return bytes.Buffer{}, fmt.Errorf("no object file found in rlib archive '%s'", rlibPath)
+		}
 		if err != nil {
-			log.Fatalf("%v", err)
+			return bytes.Buffer{}, fmt.Errorf("failed to read rlib archive '%s': %w", rlibPath, err)
 		}
 		if header.Name == "//" { // "//" is used in GNU ar format as a store for long file names
 			fileBuf := bytes.Buffer{}

internal/sourceanalysis/rust_test.go

@@ -2,6 +2,7 @@ package sourceanalysis
 
 import (
 	"bytes"
+	"fmt"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -103,3 +104,30 @@ func Test_rustBuildSource(t *testing.T) {
 		}
 	}
 }
+
+// An ar archive with no object file member is not an rlib we can analyse, so it should return
+// an error.
+func Test_extractRlibArchive_noObjectFile(t *testing.T) {
+	t.Parallel()
+
+	// Built by hand so the test needs no `ar` binary on the machine running it.
+	var archive bytes.Buffer
+	archive.WriteString("!<arch>\n")
+	const content = "hi"
+	// name[16] mtime[12] uid[6] gid[6] mode[8] size[10] fmag[2]
+	fmt.Fprintf(&archive, "%-16s%-12d%-6d%-6d%-8s%-10d`\n", "a.txt/", 0, 0, 0, "100644", len(content))
+	archive.WriteString(content)
+
+	path := filepath.Join(t.TempDir(), "not-an-rlib.rlib")
+	if err := os.WriteFile(path, archive.Bytes(), 0600); err != nil {
+		t.Fatalf("failed to write test archive: %v", err)
+	}
+
+	_, err := extractRlibArchive(path)
+	if err == nil {
+		t.Fatal("expected an error for an ar archive with no object file, got nil")
+	}
+	if !strings.Contains(err.Error(), "no object file found") {
+		t.Errorf("expected a 'no object file found' error, got: %v", err)
+	}
+}