Implement validation of nested schema

[mirpedrol]

Implement validation of nested schema.
For example, maps or nf-core igenomes.

[awgymer]

Does this ticket also cover simple arrays?

[mirpedrol]

To add more context, this issue comes from the original issue in nf-core nf-core/tools#1554

Simple arrays should already be validated with "type": "array", however I haven't tested it. Do you have a test case to verify that?

[awgymer]

May be some crossed wires here.
I specifically am wanting to use yaml (or json) samplesheets with an array field.
My specific case is that I have a pipeline which does tumour/normal analysis and can take an arbitrary number of tumour input files for any given normal.
i.e. something like

---
- 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.

[mirpedrol]

I see, then this is worth a different issue, as it is a functionality for the channel factory more than validation. Thanks for pointing this use case out :)

[nvnieuwk]

Maybe we should also look into implementing this in version 2.0?