Expand relative mask_path and make paths valid for used OS (#3257)

fiftyone/core/utils.py

@@ -1368,6 +1368,41 @@ def safe_relpath(path, start=None, default=None):
     return relpath
 
 
+def expand_mask_paths(sample, rel_path):
+    """Finds all `mask_path` keys inside a serialized sample recursively and expand relative paths.
+    It is assumed that `mask_path` can only exist in `dict`.
+
+    Args:
+        sample: a serialized sample
+        rel_path: part of path to make relative paths absolute
+    """
+    if isinstance(sample, dict):
+        for key, value in sample.items():
+            if key == "mask_path" and not os.path.isabs(key):
+                expanded = os.path.join(rel_path, value)
+                sample[key] = make_path_os_safe(expanded)
+            elif isinstance(value, (dict, list, tuple)):
+                expand_mask_paths(value, rel_path)
+    elif isinstance(sample, (list, tuple)):
+        for item in sample:
+            expand_mask_paths(item, rel_path)
+
+
+def make_path_os_safe(path):
+    """Convert path delimiters depending on OS.
+
+    Args:
+        path: path to make OS safe
+
+    Returns:
+        valid path
+    """
+    if sys.platform == "win32":
+        return path.replace("/", "\\")
+    else:
+        return path.replace("\\", "/")
+
+
 def compute_filehash(filepath, method=None, chunk_size=None):
     """Computes the hash of the given file.
 

fiftyone/utils/data/importers.py

@@ -1848,6 +1848,7 @@ def _import_samples(self, dataset, dataset_dict, tags=None):
         def _parse_sample(sd):
             if not os.path.isabs(sd["filepath"]):
                 sd["filepath"] = os.path.join(rel_dir, sd["filepath"])
+                sd["filepath"] = fou.make_path_os_safe(sd["filepath"])
 
             if tags is not None:
                 sd["tags"].extend(tags)
@@ -1856,6 +1857,10 @@ def _parse_sample(sd):
                 _parse_media_fields(sd, media_fields, rel_dir)
 
             sd["_dataset_id"] = dataset_id
+
+            # Find all mask_path keys recursively and expand relative paths
+            fou.expand_mask_paths(sd, rel_dir)
+
             return sd
 
         sample_ids = foo.insert_documents(