I have two files in input and one of them may be not exists. There is an image attached to this post. The second branch is the right solution (in my version not exists the "if flow variable"). The first branch is the same whit a try/catch and doesn't works. If a file non exists the workflow stopped the execution. Why?
If i can't use the try/catch in this method which is the right use?
actually i noticed the same problems. Some reader nodes can be used with try and catch to find not existing files... and some unfortunately not (usually these evaluate the workflow variable independent from the workflow execution state).
Works: CSV Reader <-> Works not XLS Reader
Generally, I think there needs to be some polishing for readers/writers to make their behaviour more consistent, e.g. some accept file:// urls... some not. This can be a really frustrating experience for a KNIME beginner.