Gradle Isolated Projects Incompatibility

When you try to enable Isolated Projects in paperweight project (paperweight-userdev plugin), you catch such error:

org.gradle.api.InvalidUserCodeException: Cannot call 'getByName(String)' on BuildServicesRegistry.getRegistrations()
when Isolated Projects is enabled. Only 'findByName(String)' is permitted. Alternatively, use
BuildServicesRegistry.registerIfAbsent(String, Class) if possible.

Gradle 10 enables configuration cache by default (and paperweight already supports this) and then (in future releases) enables Isolated Projects which would speed up build for multi-model projects in configuration stage by many times.

Here's my settings to reproduce this:

Environment

• Gradle 9.7.0
• io.papermc.paperweight.userdev 2.0.0-beta.21
• Kotlin 2.2.0, JVM 21 toolchain
• org.gradle.configuration-cache=true already enabled and working; org.gradle.isolated-projects=true is what we're trying to turn on
• ~110 total modules count and ~30 with paperweight

Reproduction

1. Apply io.papermc.paperweight.userdev to any project.
2. Set org.gradle.isolated-projects=true.
3. Run any task that configures that project, e.g. ./gradlew help.

Root cause

Full stack trace from the configuration-cache problems report:

org.gradle.api.InvalidUserCodeException: Cannot call 'getByName(String)' on BuildServicesRegistry.getRegistrations()
when Isolated Projects is enabled. Only 'findByName(String)' is permitted. Alternatively, use
BuildServicesRegistry.registerIfAbsent(String, Class) if possible.

    at org.gradle.api.internal.DelegatingNamedDomainObjectSet.getByName(DelegatingNamedDomainObjectSet.java:145)
    at io.papermc.paperweight.util.UtilsKt.getDownload(utils.kt:115)
    at io.papermc.paperweight.userdev.PaperweightUser$createSetup$ret$1$1.execute(PaperweightUser.kt:378)
    at io.papermc.paperweight.userdev.PaperweightUser$createSetup$ret$1$1.execute(PaperweightUser.kt:376)
    at io.papermc.paperweight.userdev.PaperweightUser$createSetup$ret$1.execute(PaperweightUser.kt:376)
    at io.papermc.paperweight.userdev.PaperweightUser$createSetup$ret$1.execute(PaperweightUser.kt:375)
    at io.papermc.paperweight.userdev.PaperweightUser.createSetup(PaperweightUser.kt:413)
    at io.papermc.paperweight.userdev.PaperweightUser.apply$lambda$3(PaperweightUser.kt:101)

UtilsKt.getDownload() (utils.kt:115) looks up an existing shared BuildService registration via project.gradle.sharedServices.registrations.getByName(name) instead of findByName(name) or registerIfAbsent(name, Class). Under IP, BuildServicesRegistry.getRegistrations() only permits findByName; getByName is explicitly disallowed because it materializes/queries a registration in a way IP can't isolate across projects. This path runs for every project PaperweightUser (i.e. the paperweight-userdev plugin) is applied to, in PaperweightUser.apply() → createSetup() → the download shared-service lookup — so it reproduces identically on any Bukkit module in a multi-module build that uses this plugin, not just ours.

Start at UtilsKt.getDownload in utils.kt:115 and trace the shared BuildService lookup from PaperweightUser.kt:375-413. Reproduce with Gradle 9.7, isolated projects enabled, and ./gradlew help. Done means the paperweight-userdev plugin configures without the InvalidUserCodeException under isolated projects.