Heads-up! The fixes that make Gradle's generated API JAR a correctly-functioning automatic module have been released with Gradle 6.0-rc-2! [1]
The so-called „shaded“ JAR file is not distributed like other Gradle artifacts. Instead, it is generated lazily whenever you're developing a Gradle plugin. It lives at {$GRADLE_USER_HOME}/caches/6.0-rc-2/generated-gradle-jars/gradle-api-6.0-rc-2.jar. Sincere thanks to Cédric Champeau (melix), Sterling Greene (big-guy), Alan Bateman, Jochen Theodorou (blackdrag) and Alex Buckley! --- [1] http://bit.ly/GrdlisAmodule