`nextflow launch` validate parameters prior to running pipeline

[adamrtalbot]

New feature

Currently, it is possible to run an invalid pipeline with nextflow launch

e.g. nextflow launch nf-core/rnaseq (no parameters!) will start and cause a large delay (high latency) before failing (required arguments, --input and --outdir).

Use case

Validate a pipeline early before sending to Seqera Platform.

Suggested implementation

It's not practical to run the contents of the pipeline really, but some early validation should be performed.

We could either:

• Validate against the nextflow_schema.json or config options before sending to Platform
  • Will validate parameters early but can't do anything about invalid contents
• Use -preview or nextflow inspect could be used internally to do run a mock pipeline
  • Will do a deeper check, but likely to trip up over authentication or access issues which will deviate from the remote compute environment
• Validate on platform, return the yes or no signal back to Nextflow
  • More complicated, requires extensive engineering on both sides.