watcher: ensure we create target mount point for storage

We would only create the target when updating files. We need to make
sure that we create the target if the source is a directory. Without
this, we'll fail to start a container that utilizes an empty configmap,
for example.

Add unit tests for this.

Fixes: #2638

Signed-off-by: Eric Ernst <eric_ernst@apple.com>

src/agent/src/watcher.rs

@@ -269,6 +269,19 @@ impl SandboxStorages {
             let entry = Storage::new(storage)
                 .await
                 .with_context(|| "Failed to add storage")?;
+
+            // If the storage source is a directory, let's create the target mount point:
+            if entry.source_mount_point.as_path().is_dir() {
+                fs::create_dir_all(&entry.target_mount_point)
+                    .await
+                    .with_context(|| {
+                        format!(
+                            "Unable to mkdir all for {}",
+                            entry.target_mount_point.display()
+                        )
+                    })?;
+            }
+
             self.0.push(entry);
         }
 
@@ -472,6 +485,85 @@ mod tests {
         Ok((storage, src_path))
     }
 
+    #[tokio::test]
+    async fn test_empty_sourcedir_check() {
+        //skip_if_not_root!();
+        let dir = tempfile::tempdir().expect("failed to create tempdir");
+
+        let logger = slog::Logger::root(slog::Discard, o!());
+
+        let src_path = dir.path().join("src");
+        let dest_path = dir.path().join("dest");
+        let src_filename = src_path.to_str().expect("failed to create src filename");
+        let dest_filename = dest_path.to_str().expect("failed to create dest filename");
+
+        std::fs::create_dir_all(src_filename).expect("failed to create path");
+
+        let storage = protos::Storage {
+            source: src_filename.to_string(),
+            mount_point: dest_filename.to_string(),
+            ..Default::default()
+        };
+
+        let mut entries = SandboxStorages {
+            ..Default::default()
+        };
+
+        entries
+            .add(std::iter::once(storage), &logger)
+            .await
+            .unwrap();
+
+        assert!(entries.check(&logger).await.is_ok());
+        assert_eq!(entries.0.len(), 1);
+
+        assert_eq!(std::fs::read_dir(src_path).unwrap().count(), 0);
+        assert_eq!(std::fs::read_dir(dest_path).unwrap().count(), 0);
+        assert_eq!(std::fs::read_dir(dir.path()).unwrap().count(), 2);
+    }
+
+    #[tokio::test]
+    async fn test_single_file_check() {
+        //skip_if_not_root!();
+        let dir = tempfile::tempdir().expect("failed to create tempdir");
+
+        let logger = slog::Logger::root(slog::Discard, o!());
+
+        let src_file_path = dir.path().join("src.txt");
+        let dest_file_path = dir.path().join("dest.txt");
+
+        let src_filename = src_file_path
+            .to_str()
+            .expect("failed to create src filename");
+        let dest_filename = dest_file_path
+            .to_str()
+            .expect("failed to create dest filename");
+
+        let storage = protos::Storage {
+            source: src_filename.to_string(),
+            mount_point: dest_filename.to_string(),
+            ..Default::default()
+        };
+
+        //create file
+        fs::write(src_file_path, "original").unwrap();
+
+        let mut entries = SandboxStorages::default();
+
+        entries
+            .add(std::iter::once(storage), &logger)
+            .await
+            .unwrap();
+
+        assert!(entries.check(&logger).await.is_ok());
+        assert_eq!(entries.0.len(), 1);
+
+        // there should only be 2 files
+        assert_eq!(std::fs::read_dir(dir.path()).unwrap().count(), 2);
+
+        assert_eq!(fs::read_to_string(dest_file_path).unwrap(), "original");
+    }
+
     #[tokio::test]
     async fn test_watch_entries() {
         skip_if_not_root!();