fix(dir): report an error instead of panicking when the path is missing

pkg/dir/dir.go

@@ -42,10 +42,15 @@ func CheckFileExist(path string) bool {
 func DirSize(path string) (int64, error) {
 	var size int64
 	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
+		// filepath.Walk passes a nil info when it cannot stat the root, so the
+		// error has to be handled before info is dereferenced.
+		if err != nil {
+			return err
+		}
 		if !info.IsDir() {
 			size += info.Size()
 		}
-		return err
+		return nil
 	})
 	return size, err
 }

pkg/dir/dir_test.go

@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package dir
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDirSize(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "a.txt"), []byte("12345"), 0o600))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "b.txt"), []byte("1234567890"), 0o600))
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "sub"), 0o700))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "sub", "c.txt"), []byte("1234567"), 0o600))
+
+	size, err := DirSize(dir)
+	require.NoError(t, err)
+	assert.Equal(t, int64(22), size)
+}
+
+// A path that does not exist must be reported as an error. Before the fix
+// filepath.Walk hands the callback a nil FileInfo for the root, and
+// `info.IsDir()` panicked with a nil pointer dereference instead.
+func TestDirSizeMissingPath(t *testing.T) {
+	missing := filepath.Join(t.TempDir(), "no-such-dir")
+
+	size, err := DirSize(missing)
+	require.Error(t, err)
+	assert.Equal(t, int64(0), size)
+}
+
+// Same for a path whose parent is missing, and for a relative path that
+// cannot be resolved from the working directory.
+func TestDirSizeMissingPathsDoNotPanic(t *testing.T) {
+	for _, missing := range []string{"no/such/relative/dir", "/no/such/absolute/dir"} {
+		t.Run(missing, func(t *testing.T) {
+			size, err := DirSize(missing)
+			require.Error(t, err)
+			assert.Equal(t, int64(0), size)
+		})
+	}
+}