warn on nonempty image directory

tools/copy_bom/src/bom.rs

@@ -9,7 +9,7 @@ use crate::error::{FILE_NOT_EXISTS_ERROR, INVALID_BOM_FILE_ERROR};
 use crate::util::{
     check_file_hash, copy_dir, copy_file, copy_shared_object, create_link, dest_in_root,
     find_dependent_shared_objects, find_included_bom_file, infer_default_loader,
-    lazy_check_missing_libraries, mkdir, resolve_envs,
+    lazy_check_missing_libraries, mkdir, resolve_envs, warn_on_nonempty_image_dir,
 };
 use serde::{Deserialize, Serialize};
 use serde_yaml;
@@ -107,6 +107,7 @@ impl Bom {
         dry_run: bool,
         included_dirs: &Vec<String>,
     ) {
+        warn_on_nonempty_image_dir(root_dir);
         // We need to keep the order of boms and bom managements
         let mut sorted_boms = Vec::new();
         let mut bom_managements = Vec::new();

tools/copy_bom/src/util.rs

@@ -579,3 +579,22 @@ pub fn lazy_check_missing_libraries(image_dir: &str) {
         std::process::exit(MISSING_LIBRARY_ERROR);
     }
 }
+
+/// Print warn message if image directory is not empty.
+/// The image dir should be empty before running copy_bom so copy bom can track all files to copy in bom file.
+/// Users can ignore the warning now if they are sure the image directory contains correct contents.
+pub fn warn_on_nonempty_image_dir(image_dir: &str) {
+    let image_path_buf = PathBuf::from(image_dir);
+    let image_path = image_path_buf.as_path();
+    if image_path.is_dir() {
+        if let Ok(read_dir) = image_path.read_dir() {
+            let dir_entries = read_dir.collect::<Vec<_>>();
+            if dir_entries.len() > 0 {
+                println!(
+                    "WARNING: {} is not an empty directory before running copy_bom.",
+                    image_dir
+                );
+            }
+        }
+    }
+}