Apply rules: replacing a text string doesn't seem possible?

[hexylena]

Describe the bug

I want to use "create column from regex replacement" to delete a substring (retaining the rest)

Galaxy Version and/or server at which you observed the bug
Browser and Operating System
same as #19102

To Reproduce
Steps to reproduce the behavior:

1. Create a collection with asdf.fa and bsdf and a second collection with asdf.fa and bsdf.fa
2. Apply rules
3. Column
4. Using a regular expression
5. Create column from expression replacement
6. Regex: .fa
7. Replacement: `` (nothing)

What happens

The regex fails, failing to match some datasets.

If every dataset ends in .fa, instead it fails by creating a column with just .fa, because the rule sees the empty replacement and decides I actually meant to do "create column matching expression".

Expected behavior

I expect this to behave like cat | sed 's/a/b/g but it isn't. I expect it to be providing the entire identifier as input, and then doing the requested replacement (.fa with nothing) which shouldn't fail.

[hexylena]

For others encountering the same I'm using the following workflow as a workaround. It is not ideal but it works. Maybe it is useful as inspiration.

Galaxy-Workflow-Sanitize_Filename.ga.txt