fix(cli): Handle empty ignore files more gracefully

Fixes: aquasecurity#7934

pkg/flag/report_flags_test.go

@@ -221,4 +221,6 @@ func TestReportFlagGroup_ToOptions(t *testing.T) {
 		_, err := f.ToOptions()
 		assert.ErrorContains(t, err, "ignore file not found: doesntexist")
 	})
+
+	t.Run("")
 }

pkg/result/ignore.go

@@ -183,8 +183,9 @@ func (c *IgnoreConfig) MatchLicense(licenseID, filePath string) *IgnoreFinding {
 
 func ParseIgnoreFile(ctx context.Context, ignoreFile string) (IgnoreConfig, error) {
 	var conf IgnoreConfig
-	if _, err := os.Stat(ignoreFile); errors.Is(err, fs.ErrNotExist) {
-		// .trivyignore doesn't necessarily exist
+	if fi, err := os.Stat(ignoreFile); errors.Is(err, fs.ErrNotExist) || fi.Size() == 0 {
+		// .trivyignore doesn't necessarily exist or maybe empty
+		log.Debug("Specified ignore file does not exist or is empty", log.String("file", ignoreFile), log.Int64("size", fi.Size()))
 		return IgnoreConfig{}, nil
 	} else if filepath.Ext(ignoreFile) == ".yml" || filepath.Ext(ignoreFile) == ".yaml" {
 		conf, err = parseIgnoreYAML(ignoreFile)

pkg/result/ignore_test.go

@@ -0,0 +1,77 @@
+package result
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseIgnoreFile(t *testing.T) {
+	t.Run("happy path valid config file", func(t *testing.T) {
+		got, err := ParseIgnoreFile(context.TODO(), "testdata/.trivyignore")
+		require.NoError(t, err)
+		assert.Equal(t, "testdata/.trivyignore", got.FilePath)
+
+		// IDs in .trivyignore are treated as IDs for all scanners
+		// as it is unclear which type of security issue they are
+		assert.Len(t, got.Vulnerabilities, 6)
+		assert.Len(t, got.Misconfigurations, 6)
+		assert.Len(t, got.Secrets, 6)
+		assert.Len(t, got.Licenses, 6)
+	})
+
+	t.Run("happy path valid YAML config file", func(t *testing.T) {
+		got, err := ParseIgnoreFile(context.TODO(), "testdata/.trivyignore.yaml")
+		require.NoError(t, err)
+		assert.Equal(t, "testdata/.trivyignore.yaml", got.FilePath)
+		assert.Len(t, got.Vulnerabilities, 5)
+		assert.Len(t, got.Misconfigurations, 3)
+		assert.Len(t, got.Secrets, 3)
+		assert.Len(t, got.Licenses, 1)
+	})
+
+	t.Run("empty YAML file passed", func(t *testing.T) {
+		f, err := os.CreateTemp("", "TestParseIgnoreFile-*.yaml")
+		require.NoError(t, err)
+		defer os.Remove(f.Name())
+
+		got, err := ParseIgnoreFile(context.TODO(), f.Name())
+		require.NoError(t, err)
+		assert.Empty(t, got)
+	})
+
+	t.Run("invalid YAML file passed", func(t *testing.T) {
+		f, err := os.CreateTemp("", "TestParseIgnoreFile-*.yaml")
+		require.NoError(t, err)
+		defer os.Remove(f.Name())
+		_, _ = f.WriteString("this file is not a yaml file")
+
+		got, err := ParseIgnoreFile(context.TODO(), f.Name())
+		assert.Contains(t, err.Error(), "yaml decode error")
+		assert.Empty(t, got)
+	})
+
+	// TODO(simar7): This test currently fails as we don't validate
+	// the correctness of ignore file when not in YAML format
+	/*
+		t.Run("invalid file passed", func(t *testing.T) {
+			f, err := os.CreateTemp("", "TestParseIgnoreFile-*")
+			require.NoError(t, err)
+			defer os.Remove(f.Name())
+			_, _ = f.WriteString("this file is not a valid trivyignore file")
+
+			_, err = ParseIgnoreFile(context.TODO(), f.Name())
+			require.Error(t, err)
+		})
+	*/
+
+	t.Run("non existing file passed", func(t *testing.T) {
+		got, err := ParseIgnoreFile(context.TODO(), "does-not-exist.yaml")
+		require.NoError(t, err)
+		assert.Empty(t, got)
+	})
+
+}