ImportTSV job skips bad records by default (keeps a count though). -Dimporttsv.skip.bad.lines=false can be used to fail if a bad row is encountered.
To be easily able to determine which rows are corrupted in an input, rather than failing on one row at a time seems like a good feature to have.
Moreover, there should be 'dry-run' functionality in such kinds of tools, which can essentially does a quick run of tool without making any changes but reporting any errors/warnings and success/failure.
To identify corrupted rows, simply logging them should be enough. In worst case, all rows will be logged and size of logs will be same as input size, which seems fine. However, user might have to do some work figuring out where the logs. Is there some link we can show to the user when the tool starts which can help them with that?
For the dry run, we can simply use if-else to skip over writing out KVs, and any other mutations, if present.