Add Column by Fetching URL silently fails on malformed URLs

[tfmorris]

If an invalid URL is used for the Add Column by Fetching URLs operation, the operation silently results in a null value instead of an error, making it much more difficult for the user to figure out what the problem is. This was recently on the forum as a cause of confusion for a user: https://forum.openrefine.org/t/fetching-urls-with-arabic-values/1036/1

This behavior was checked by a test, so I coded the new HTTP support to mimic it, but I think the test is wrong and we should fix both it and the code so that URL/URI errors get reported to the user in an intelligible fashion.

To Reproduce

Steps to reproduce the behavior:

1. Create a project with a cell containing the text: https://transliterate.qcri.org/ar2en/احمد احمد
2. Select Add a Column by Fetching URLs
3. For "On error:" select "store error"

Current Results

The operation silently fails with no error stored in the cell.

Expected Behavior

The cell value should be set to an EvalError with the appropriate error code/message.

Versions

• OpenRefine: 3.8-snapshot (ie current HEAD)