App metadata at runtime

Your About dialog wants 1.2.3. Your crash reporter wants com.example.myapp. Your auto-updater wants the vendor. None of these should be hardcoded — and none of them should be re-read off the filesystem at runtime. NucleusApp exposes what the Gradle plugin injected at build time, with sensible fallbacks for ./gradlew run.

TL;DR

• Singleton NucleusApp exposes appId, version, vendor, description, appName, aumid, startupTaskId, isConfigured.
• Injected by the Gradle plugin via system properties (during run) and a classpath resource (nucleus/nucleus-app.properties, in packaged builds).
• All values are String? except appId (which falls back to the main class name) and isConfigured.
• Several Nucleus modules read it implicitly — SingleInstanceManager, taskbar-progress, autolaunch, updater-runtime.

Install

Comes with core-runtime.

Quickstart

import dev.nucleusframework.core.runtime.NucleusApp

@Composable
fun AboutDialog() {
    Column {
        Text(NucleusApp.appName ?: NucleusApp.appId)
        NucleusApp.version?.let { Text("Version $it") }
        NucleusApp.vendor?.let { Text("by $it") }
    }
}

if (NucleusApp.isConfigured) {
    // Running as a packaged app
    initAutoUpdater()
}

How it works

The plugin gives NucleusApp two delivery channels:

1. System properties during ./gradlew run: -Dnucleus.app.id=MyApp, -Dnucleus.app.version=..., etc.
2. Classpath resource in packaged builds: nucleus/nucleus-app.properties baked into the app jar.

Resolution is first-non-null-wins: system property, then resource, then a legacy fallback for appId (main class name from sun.java.command, or "NucleusApp").

This is the seam that lets a one-liner in build.gradle.kts flow into every runtime module without you wiring it up by hand. The single-instance lock identifier, the AUMID Windows uses for badge counts, the WM_CLASS GraalVM sets on Linux, the update marker directory — all of them go through NucleusApp and pick up whatever you declared in the plugin.

Reference

NucleusApp

Notes

• A common pattern: branch on NucleusApp.isConfigured to gate auto-update, telemetry, anything you don't want firing in dev.
• See ExecutableRuntime when you need to distinguish DMG vs Flatpak vs ./gradlew run — that's a separate concern from metadata.