Support pipeline composition

[bentsherman]

Language server support for pipeline composition (nextflow-io/nextflow#7213): a pipeline -- the params / workflow / output trio of a script -- can be included as a named workflow.

include {
    params as RnaseqParams ;
    workflow as NFCORE_RNASEQ
} from './pipelines/nf-core/rnaseq'

workflow {
    main:
    rnaseq = NFCORE_RNASEQ( params.rnaseq )
    ...
}

Important

Draft: this does not build yet. It needs two nf-lang additions from nextflow-io/nextflow#7213 that are not released. See Release ordering.

The suite here is green only against a local nf-lang built from that branch, resolved via mavenLocal() over the pinned 26.08.0-edge. That build is also ahead of the v26.08.0-edge tag by the twelve nf-lang commits merged to master since, including #7557 and #7342. This branch has never been built against the released artifact, and cannot be until nf-lang is cut -- the two hooks are missing from it.

Include resolution itself comes for free -- the language server runs nf-lang's own ResolveIncludeVisitor -- so this PR covers only what the language server implements itself.

Changes

Calling a pipeline (TypeCheckingVisitorEx)

A pipeline declares its inputs with a params block rather than a take: section, so its entry workflow has no parameters. Every pipeline call therefore reported Workflow `NFCORE_RNASEQ` expects 0 argument(s) but received 1, and the call's return type was inferred as void.

checkPipelineCall handles the call against the pipeline instead:

• Named arguments are checked against the params block -- unknown param, missing required param, and argument type. A param is required when it has no default and is not nullable.
• The return type is a record of the output declarations, matching the record the pipeline returns at runtime, so rnaseq.bams resolves and rnaseq.counts is reported.
• A single non-map argument (NFCORE_RNASEQ( params.rnaseq + record(input: ch) )) is left to the runtime params validation, rather than modelling record arithmetic here.

Named arguments also get _NAMED_PARAM metadata, so go-to-definition on one lands on the param declaration.

Navigation and hover

• The params and output blocks of an included pipeline are record types synthesized for the include. They are not in any file's AST, so they have no URI and go-to-definition silently did nothing. getDefinition now redirects such a type to the block it was synthesized from.

• An entry workflow rendered as workflow <entry> on hover. It is now rendered as the pipeline it belongs to, which is the signature a caller needs:

  pipeline {
      params:
      input: Path
      aligner: String = 'star'
  
      output:
      bams: Channel<Path>
  }
  

Null-name guards

An included pipeline is a WorkflowNode with no name of its own. Two places assumed otherwise:

• WorkspacePreviewProvider.children passed the name straight to Map.of, which rejects null values.
• DataflowVisitor.visitPipeline labelled a piped call with it, producing an unlabelled DAG node. It now uses the alias.

Tests

ScriptPipelineCompositionTest, six cases: no diagnostics for a full three-block include, definition of an included params block, pipeline hover, unknown param, missing param, and output type inference. Full suite green.

Not included

• Completion inside include { ... } for workflow, params and output. There is no completion there at all today, so nothing regressed, but it is where these are least discoverable.
• Go-to-definition on a type annotation. Parameter types are not indexed by ASTParentVisitor, so this has never worked for any record type -- not specific to pipeline composition.
• Workspace symbols still show every pipeline as workflow <entry>.

Release ordering

1. Pipeline composition nextflow#7213 merges -- it adds the two hooks this PR needs:
   • ResolveIncludeVisitor.getPipelineBlock(ClassNode), for navigating to an included params/output block.
   • ScriptNode.getPipeline(WorkflowNode), for resolving a pipeline's blocks from a call to it.
2. nf-lang release
3. Bump io.nextflow:nf-lang here, mark this PR ready
4. Language server release