Add Nextflow language server support (#1815)

The Nextflow language server schedules a debounced (1s) AST update on every
didOpen/didChange, and LanguageService.references is the only request that does
not await it -- documentSymbol, codeLens, documentLink and semanticTokensFull
all do. A references request issued inside that window races the recompile of
the file it asks about and can return an empty list, which is what the macOS CI
runner hit. Send a documentSymbol request for the same file first, which blocks
server-side until the pending update has been applied.

Also compare reference paths using the platform separator in the tests, since
relativePath is OS-native and the hardcoded forward slashes failed on Windows.

test/resources/repos/nextflow/test_repo/.gitignore

@@ -0,0 +1,3 @@
+work/
+.nextflow/
+.nextflow.log*

test/resources/repos/nextflow/test_repo/main.nf

@@ -0,0 +1,23 @@
+#!/usr/bin/env nextflow
+
+include { GREET; SHOUT } from './modules/greet/main.nf'
+include { buildGreeting } from './modules/util/main.nf'
+
+params.names = ['Ada', 'Grace']
+
+workflow SAY_HELLO {
+    take:
+    names
+
+    main:
+    greetings = GREET(names)
+    shouted = SHOUT(greetings)
+
+    emit:
+    shouted
+}
+
+workflow {
+    log.info buildGreeting('World')
+    SAY_HELLO(Channel.fromList(params.names))
+}

test/resources/repos/nextflow/test_repo/modules/greet/main.nf

@@ -0,0 +1,27 @@
+process GREET {
+    tag "$name"
+
+    input:
+    val name
+
+    output:
+    path "greeting.txt"
+
+    script:
+    """
+    echo "Hello, ${name}!" > greeting.txt
+    """
+}
+
+process SHOUT {
+    input:
+    path greeting
+
+    output:
+    path "shout.txt"
+
+    script:
+    """
+    tr '[:lower:]' '[:upper:]' < ${greeting} > shout.txt
+    """
+}

test/resources/repos/nextflow/test_repo/modules/util/main.nf

@@ -0,0 +1,7 @@
+def normalizeName(String name) {
+    return name.trim().toLowerCase()
+}
+
+def buildGreeting(String name) {
+    return "Hello, " + normalizeName(name)
+}

test/resources/repos/nextflow/test_repo/nextflow.config

@@ -0,0 +1,8 @@
+manifest {
+    name = 'serena-nextflow-test-repo'
+    description = 'Minimal Nextflow pipeline used by the solidlsp Nextflow language server tests'
+}
+
+process {
+    cpus = 1
+}