Secondary variants of resolvable configuration aren't displayed in outgoingVariants report

[aSemy]

Current Behavior

Secondary variants of resolvable configuration aren't displayed in outgoingVariants report.

Expected Behavior

Either:

1. Secondary variants of resolvable configuration are displayed in outgoingVariants report.
2. If secondary variants of resolvable configurations are not valid, it should not be possible to create them.

Context (optional)

Related: #28149

Steps to Reproduce

// build.gradle.kts

group = "x.y.z"
version = "1.2.3"

val fooFiles: Configuration by configurations.creating {
  isCanBeDeclared = false
  isCanBeResolved = true
  isCanBeConsumed = false
}

val fooFilesVariant1: ConfigurationVariant by fooFiles.outgoing.variants.creating {}

val barFiles: ResolvableConfiguration = configurations.resolvable("barFiles") {}.get()

val barFilesVariant1: ConfigurationVariant by barFiles.outgoing.variants.creating {}

Run gradle outgoingVariants -q

--------------------------------------------------
Variant archives
--------------------------------------------------
Configuration for archive artifacts.

Capabilities
    - x.y.z:demo:1.2.3 (default capability)

--------------------------------------------------
Variant default
--------------------------------------------------
Configuration for default artifacts.

Capabilities
    - x.y.z:demo:1.2.3 (default capability)

Gradle version

8.7

Build scan URL (optional)

No response

Your Environment (optional)

No response

[ov7a]

The issue is in the backlog of the relevant team and is prioritized by them.

[abstratt]

Note that if you mark a configuration as isCanBeConsumed = false, outgoing should not be called on it:

Usage: This method should only be called on consumable configurations, but will not warn if used otherwise.

Maybe not silently accepting outgoing to be accessed in a non-consumable configuration is exactly what is being asked for here.

Also, if you do leave it as consumable (the default), but also leave it as resolvable, that makes it a legacy configuration (see table in this section), and then it is not shown by default, only when --all is specified.

[abstratt]

Also note that even for the project as-is, if you specify the configuration name explicitly, it will show the variant:

gradle outgoingVariants --variant fooFiles 

> Task :outgoingVariants
--------------------------------------------------
Variant fooFiles
--------------------------------------------------

Capabilities
    - x.y.z:configurations:1.2.3 (default capability)

Secondary Variants (*)

    --------------------------------------------------
    Secondary Variant fooFilesVariant1
    --------------------------------------------------
    
(*) Secondary variants are variants created via the Configuration#getOutgoing(): ConfigurationPublications API which also participate in selection, in addition to the configuration itself.

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1 actionable task: 1 executed