Unless I misunderstand what you're asking for, this should already be the case. For instance, if a workflow step takes in a file of 'tabular' type, only tabular files (and subtypes, including interval, etc.) should be presented as dropdowns in the list. Types such as plain text, binary files, etc., should be excluded. Are you seeing other behavior?

I am developing a custom workflow in galaxy. I have 4 input files that need to be fed into various steps of the workflow. I would like to be able to specify a data type for the inputs such that the pre-populated drop downs are filtered to datasets of the appropriate type as well as being able to do some simple validation before the workflow begins. Is there someway to do this?

Thanks much,

Ann
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