Print DSL-based Gradle Version Catalog as TOML - useful to migrate from kotlin-defined dependencies to a TOML-based version catalog.

catalog_to_toml.gradle.kts

val versionLines = mutableListOf<String>()
val libs = mutableMapOf<String, List<String>>()
val plugs = mutableMapOf<String, List<String>>()
versionCatalogs.forEach { catalog ->
	// map of version - alias | needed to guess the aliases used
	val versions = catalog.versionAliases.associate { alias ->
		val version = catalog.findVersion(alias)
		version.get().displayName to alias.replace(".", "-")
	}
	versionLines += versions.map { (value, key) -> "$key = \"$value\"" }.joinToString("\n").trim('\n')
	fun buildLibraries(): List<String> {
		return catalog.libraryAliases.map { ogAlias ->
			// toml version catalogs, despite the docs, don't support dots in keys
			val alias = ogAlias.replace(".", "-")
			val lib = catalog.findLibrary(alias).get().get()
			val version = versions[lib.version]?.let { "version.ref = \"$it\"" }
				?: "version = \"${lib.version}\""
			"$alias = { group = \"${lib.group}\", name = \"${lib.name}\", $version }"
		}
	}
	fun buildPlugins(): List<String> {
		return catalog.pluginAliases.map { ogAlias ->
			val alias = ogAlias.replace(".", "-")
			val lib = catalog.findPlugin(alias).get().get()
			val version = versions[lib.version.toString()]?.let { "version.ref = \"$it\"" }
				?: "version = \"${lib.version}\""
			"$alias = { id = \"${lib.pluginId}\", $version }"
		}
	}
	libs[catalog.name] = buildLibraries()
	plugs[catalog.name] = buildPlugins()
}
println("[versions]\n${versionLines.filter { it.isNotEmpty() }.joinToString("\n")}")
fun buildOutput(name: String, lines: Map<String, List<String>>, withKey: Boolean) = "[$name]\n${
	lines.mapNotNull { (key, lines) ->
		if (lines.isEmpty()) return@mapNotNull null
		else if (withKey) "${lines.joinToString("\n") { "$key-$it" }}\n"
		else lines.joinToString("\n")
	}.joinToString("\n")
}"
println("\n" + buildOutput("plugins", plugs, false))
println("\n" + buildOutput("libraries", libs, true))