Support for simple arrays in YAML samplesheets

[awgymer]

It would be great to be able to supply an arbitrary length array of files that is associated with just one other file like so:

---
- id: sample1
  normal: /path/to/some/file.bam
  tumour:
    - /path/to/tumour1.bam
    - /path/to/tumour2.bam
  cancer_type: aml

And then I would want to create some channel like: [[id: sample1], [normal_bam], [tumour_bams]]

In a perfect world that would be possible via fromSamplesheet but for now I would be happy with just having the samplesheet schema validation.

[nvnieuwk]

This could be handled by expanding the current meta field to another field that can create arrays for every input instead of only for the meta

[awgymer]

Arrays are slightly different from maps though right?
The array should support arbitrary number of values under a given key.

That said the ability to create extra maps beyond the default meta would also be great!

[nvnieuwk]

Good point! This will be a nice project to tackle during the hackathon. My main point of doubt is how we should handle the array creation in other samplesheet formats. But that could maybe be solved by a good brainstorming session

[nvnieuwk]

@awgymer this was implemented by you, right?

[awgymer]

This is implemented by the (currently) pending #128

[nvnieuwk]

Aaah okay do you need to work on anything more there? Or should I review it?

[awgymer]

Reading the thread I think we need to put some change into a meta schema somewhere (I'm not sure exactly where?) and possibly add a couple of notes to the docs?

[nvnieuwk]

You don't need to worry about the meta schema for now. This will need to be entirely rewritten now that we use draft 2020-12. Let's do that in another PR