[SYNPY-1557] Sync a Linked Folder Bug

[BWMac]

Description

A user recently reported unexpected behavior when using the following command:

synapse get -r --followLink --downloadLocation my_folder syn123

The folder being recursively downloaded (synced) contained a link to another Synapse folder, and an error was being thrown:

FileNotFoundError: [Errno 2] No such file or directory: 'my_folder/my_linked_subfolder/SYNAPSE_METADATA_MANIFEST.tsv'

In short, the Synapse client was unable to properly mirror the folder structure with a linked folder in it. We would expect that linked folder to be created as a subfolder containing the files that it does on Synapse.

In order to enable this behavior, I first wrote an integration test to check that the client was giving the desired behavior in this situation with the expectation that the test would throw the same error until a fix was implemented. Then, I dug into the code and discovered that in _follow_link, we were previously not tracking the target name for the linked entity, which was causing a locally created folder mirroring the linked Synapse folder not to be created by the child task, resulting in the error. After adding that tracking (passing the name on to _create_task_for_child) within _follow_link, the test passed and I was able to successfully sync the folder from the original user report.

Previous behavior for syncing "normal" child folders and files was not adversely effected by the change. I tested this manually on my own test project, on the location reported by the user, and through ensuring that the existing integration tests still pass.

[BryanFauble]

Thanks for the patch!

[thomasyu888]

🔥 Great find.