List of issues with exchange interface

[lzach]

These are just some notes on what issues I have found in the exchange interface between nbgrader and the database. It could at some point be split into individual issues.

• Desync issues:
  • The interface does not check whether files exist on the local notebook when querying the exchange
  • This can lead to situations where an assignment shows as downloaded even when it is not (anymore), which makes it impossible redownload
    • This can happen due to the user deleting an assignment, or if the assignment directory is change in the configuration
  • External issue: Desync issue between nbgrader and nbexchange #14
• Paths
  • The handling of paths is inconsistent. This is in part due to inheriting path handling from nbgrader (which has a similar problem) and in part with the changes made to interface with the external exchange.
  • While it works for now, any changes to the configuration of paths might break the application (this is also true in nbgrader)
  • External issue: Paths in nbexchange plugin #24
• Checking for negative cases
  • There are some improvements to be made, both in the plugin and the exchange tornado server to handle cases where something has gone wrong.