Collecting channel entries consisting of tuples and sending it to a process

We often have channel entries in the form of tuples containing some meta data and one or more paths. For a process, we might want to collect all the entries with collect(flat:false) or toList() and send the resulting list of tuples to a process. However, if we specify the process input as val(my_tuples), the files represented by the path objects in the tuples will not be staged properly, and path(my_tuples) doesn’t work either. Rather, the input needs to be of the form val(metas), path(paths). The transformation of the channel entries of lists of tuples into tuples of lists can be done like this:

    ["id1", file("my_file1.txt")],
    ["id2", file("my_file2.txt")],
    ["id3", file("my_file3.txt")],
).collect(flat: false)
 .map { it.transpose() }
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