[firebase_storage] Updating storage metadata replaces all existing metadata

[puf]

Describe the bug
According to the Firebase documentation you can update storage metadata via the updateMetadata API.

Only the properties specified in the metadata are updated, all others are left unmodified.

The FlutterFire documentation for the same API mimics this by:

Writable metadata properties can be deleted by passing the empty string.

This is not how it works in practice though: calling updateMetadata replaces all metadata with the information provided in the call.

To Reproduce

See https://stackoverflow.com/q/61051148

Steps to reproduce the behavior:

1. Create a StorageReference to a file that has metadata, for example: a content type.
2. Call storageReference.updateMetadata(StorageMetadata(customMetadata: {'receiver': 'ID'}));
3. All existing metadata is removed, and only the custom metadata with a single property remains.

Expected behavior

Above call should leave the existing metadata unmodified.

Additional context

As far as I can see the problem comes from _buildMetadataUploadMap, which doesn't seem to handle missing properties correctly. Calling print(_buildMetadataUploadMap(StorageMetadata(customMetadata: {'receiver': 'ID2'}))) prints:

{cacheControl: null, contentDisposition: null, contentLanguage: null, contentType: null, contentEncoding: null, customMetadata: {receiver: ID2}}

I'm pretty sure this map should only contain customMetadata in this case.

[puf]

A quick fix could be:

Map<String, dynamic> _buildMetadataUploadMap(StorageMetadata metadata) {
  var map = <String, dynamic>{
    'cacheControl': metadata.cacheControl,
    'contentDisposition': metadata.contentDisposition,
    'contentLanguage': metadata.contentLanguage,
    'contentType': metadata.contentType,
    'contentEncoding': metadata.contentEncoding,
    'customMetadata': metadata.customMetadata,
  };
  map.removeWhere((key, value) => value == null);
  return map;
}

[TahaTesser]

Hi @puf
can you please provide your flutter doctor -v and flutter run --verbose?
Also, to better address the issue, would be helpful if you could post a minimal code sample to reproduce the problem
Thank you

[puf]

Hey Taha,

The problem seems to exist in the latest code (linked above). The minimal code is in the steps-to-reproduce above, and in the Stack Overflow issue I linked.

puf

[Ehesp]

Will get this checked out & tested.

[greghesp]

@puf

I've tested this on the latest roadmap version and confirm that the updateMetadata method now updates rather than replacing

First Call

Reference ref = FirebaseStorage.instance
  .ref()
   .child('/coding.jpg');

ref.updateMetadata(SettableMetadata(
  customMetadata: <String, String>{
    'message': 'hello world',
  },
));

Other metadata:
message: morning

Second Call

Reference ref = FirebaseStorage.instance
  .ref()
   .child('/coding.jpg');

ref.updateMetadata(SettableMetadata(
  customMetadata: <String, String>{
    'userId': 'ABC123',
  },
));

Other metadata:
message: morning
userId: ABC123

[puf]

Thanks for the update Greg. Let me know once this makes it into a regular release, so I can update my answer on Stack Overflow.

[Salakar]

Took a while to get back to this issue sorry but this has been in stable for over a month now so this is ok to be closed now.

Thanks again for the report @puf 🎉