Type annotations

docs/migrations/25-10.md

@@ -8,6 +8,51 @@ This page summarizes the upcoming changes in Nextflow 25.10, which will be relea
 This page is a work in progress and will be updated as features are finalized. It should not be considered complete until the 25.10 release.
 :::
 
+## New features
+
+<h3>Type annotations</h3>
+
+Type annotations are a way to denote the *type* of a variable. They are useful both for documenting and validating your pipeline code.
+
+```nextflow
+workflow RNASEQ {
+  take:
+  reads: Channel<Path>
+  index: Channel<Path>
+
+  main:
+  samples_ch = QUANT( reads.combine(index) )
+
+  emit:
+  samples: Channel<Path> = samples_ch
+}
+
+def isSraId(id: String) -> Boolean {
+  return id.startsWith('SRA')
+}
+```
+
+The following declarations can be annotated with types:
+
+- Pipeline parameters (the `params` block)
+- Workflow takes and emits
+- Function parameters and returns
+- Local variables
+- Closure parameters
+- Workflow outputs (the `output` block)
+
+Type annotations can refer to any of the {ref}`standard types <stdlib-types>`.
+
+Type annotations can be appended with `?` to denote that the value can be `null`:
+
+```nextflow
+def x_opt: String? = null
+```
+
+:::{note}
+While Nextflow inherited type annotations of the form `<type> <name>` from Groovy, this syntax was deprecated in the {ref}`strict syntax <strict-syntax-page>`. Groovy-style type annotations are still allowed for functions and local variables, but will be automatically converted to Nextflow-stype type annotations when formatting code with the language server or `nextflow lint`.
+:::
+
 ## Breaking changes
 
 - The AWS Java SDK used by Nextflow was upgraded from v1 to v2, which introduced some breaking changes to the `aws.client` config options. See {ref}`the guide <aws-java-sdk-v2-page>` for details.

docs/process.md

@@ -655,7 +655,7 @@ hello
 
 ### Input tuples (`tuple`)
 
-The `tuple` qualifier allows you to group multiple values into a single input definition. It can be useful when a channel emits tuples of values that need to be handled separately. Each element in the tuple is associated with a corresponding element in the `tuple` definition. For example:
+The `tuple` qualifier allows you to group multiple values into a single input definition. It can be useful when a channel emits {ref}`tuples <script-tuples>` of values that need to be handled separately. Each element in the tuple is associated with a corresponding element in the `tuple` definition. For example:
 
 ```nextflow
 process cat {
@@ -1056,7 +1056,7 @@ If the command fails, the task will also fail. In Bash, you can append `|| true`
 
 ### Output tuples (`tuple`)
 
-The `tuple` qualifier allows you to output multiple values in a single channel. It is useful when you need to associate outputs with metadata, for example:
+The `tuple` qualifier allows you to output multiple values in a single channel as a {ref}`tuple <script-tuples>`. It is useful when you need to associate outputs with metadata, for example:
 
 ```nextflow
 process blast {

docs/reference/stdlib-namespaces.md

@@ -105,10 +105,7 @@ The global namespace contains globally available constants and functions.
 `sleep( milliseconds: long )`
 : Sleep for the given number of milliseconds.
 
-`tuple( collection: List ) -> ArrayTuple`
-: Create a tuple object from the given collection.
-
-`tuple( args... ) -> ArrayTuple`
+`tuple( args... ) -> Tuple`
 : Create a tuple object from the given arguments.
 
 (stdlib-namespaces-channel)=