Fail build if netty-all pulls in duplicated classes

[normanmaurer]

Motivation:

We should fail the build if netty-all pulls in dependencies that produce duplicated classes on the classpath

Modifications:

Add maven plugin to verify we not have duplicated classes on the classpath / dependencies

Result:

Related to #11791

[normanmaurer]

To test this I added some extra dependency that would cause the duplicated classes issue. The build fails with:

    ➜  netty git:(4.1) ✗ ./mvnw -pl all clean package
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Detecting the operating system and CPU architecture
[INFO] ------------------------------------------------------------------------
[INFO] os.detected.name: osx
[INFO] os.detected.arch: x86_64
[INFO] os.detected.bitness: 64
[INFO] os.detected.version: 10.16
[INFO] os.detected.version.major: 10
[INFO] os.detected.version.minor: 16
[INFO] os.detected.classifier: osx-x86_64
[INFO]
[INFO] -------------------------< io.netty:netty-all >-------------------------
[INFO] Building Netty/All-in-One 4.1.70.Final-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ netty-all ---
[INFO] Deleting /Users/norman/Documents/workspace/netty/all/target
[INFO]
[INFO] --- flatten-maven-plugin:1.2.2:clean (flatten.clean) @ netty-all ---
[INFO] Deleting /Users/norman/Documents/workspace/netty/all/.flattened-pom.xml
[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0-M3:enforce (enforce-maven) @ netty-all ---
[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0-M3:enforce (enforce-tools) @ netty-all ---
[INFO]
[INFO] --- maven-checkstyle-plugin:3.1.0:check (check-style) @ netty-all ---
[INFO] Starting audit...
Audit done.
[INFO]
[INFO] --- xml-maven-plugin:1.0.1:check-format (check-style) @ netty-all ---
[INFO]
[INFO] --- maven-dependency-plugin:2.10:get (get-jetty-alpn-agent) @ netty-all ---
[INFO] Resolving org.mortbay.jetty.alpn:jetty-alpn-agent:jar:2.0.10 with transitive dependencies
[INFO]
[INFO] --- build-helper-maven-plugin:1.10:parse-version (parse-version) @ netty-all ---
[INFO]
[INFO] --- duplicate-finder-maven-plugin:1.3.0:check (default) @ netty-all ---
[INFO] Checking compile classpath
[INFO] Checking runtime classpath
[WARNING] Found duplicate and different classes in [io.netty:netty-transport-classes-epoll:4.1.70.Final-SNAPSHOT, io.netty:netty-transport-native-epoll:4.1.69.Final]:
[WARNING]   io.netty.channel.epoll.AbstractEpollChannel
[WARNING]   io.netty.channel.epoll.AbstractEpollServerChannel
[WARNING]   io.netty.channel.epoll.AbstractEpollStreamChannel
[WARNING]   io.netty.channel.epoll.Epoll
[WARNING]   io.netty.channel.epoll.EpollChannelConfig
[WARNING]   io.netty.channel.epoll.EpollChannelOption
[WARNING]   io.netty.channel.epoll.EpollDatagramChannel
[WARNING]   io.netty.channel.epoll.EpollDatagramChannelConfig
[WARNING]   io.netty.channel.epoll.EpollDomainDatagramChannel
[WARNING]   io.netty.channel.epoll.EpollDomainDatagramChannelConfig
[WARNING]   io.netty.channel.epoll.EpollDomainSocketChannel
[WARNING]   io.netty.channel.epoll.EpollDomainSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollEventArray
[WARNING]   io.netty.channel.epoll.EpollEventLoop
[WARNING]   io.netty.channel.epoll.EpollEventLoopGroup
[WARNING]   io.netty.channel.epoll.EpollMode
[WARNING]   io.netty.channel.epoll.EpollRecvByteAllocatorHandle
[WARNING]   io.netty.channel.epoll.EpollRecvByteAllocatorStreamingHandle
[WARNING]   io.netty.channel.epoll.EpollServerChannelConfig
[WARNING]   io.netty.channel.epoll.EpollServerDomainSocketChannel
[WARNING]   io.netty.channel.epoll.EpollServerSocketChannel
[WARNING]   io.netty.channel.epoll.EpollServerSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollSocketChannel
[WARNING]   io.netty.channel.epoll.EpollSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollTcpInfo
[WARNING]   io.netty.channel.epoll.LinuxSocket
[WARNING]   io.netty.channel.epoll.Native
[WARNING]   io.netty.channel.epoll.NativeDatagramPacketArray
[WARNING]   io.netty.channel.epoll.NativeStaticallyReferencedJniMethods
[WARNING]   io.netty.channel.epoll.SegmentedDatagramPacket
[WARNING]   io.netty.channel.epoll.TcpMd5Util
[WARNING] Found duplicate classes/resources in compile classpath.
[WARNING] Found duplicate and different classes in [io.netty:netty-transport-classes-epoll:4.1.70.Final-SNAPSHOT, io.netty:netty-transport-native-epoll:4.1.69.Final]:
[WARNING]   io.netty.channel.epoll.AbstractEpollChannel
[WARNING]   io.netty.channel.epoll.AbstractEpollServerChannel
[WARNING]   io.netty.channel.epoll.AbstractEpollStreamChannel
[WARNING]   io.netty.channel.epoll.Epoll
[WARNING]   io.netty.channel.epoll.EpollChannelConfig
[WARNING]   io.netty.channel.epoll.EpollChannelOption
[WARNING]   io.netty.channel.epoll.EpollDatagramChannel
[WARNING]   io.netty.channel.epoll.EpollDatagramChannelConfig
[WARNING]   io.netty.channel.epoll.EpollDomainDatagramChannel
[WARNING]   io.netty.channel.epoll.EpollDomainDatagramChannelConfig
[WARNING]   io.netty.channel.epoll.EpollDomainSocketChannel
[WARNING]   io.netty.channel.epoll.EpollDomainSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollEventArray
[WARNING]   io.netty.channel.epoll.EpollEventLoop
[WARNING]   io.netty.channel.epoll.EpollEventLoopGroup
[WARNING]   io.netty.channel.epoll.EpollMode
[WARNING]   io.netty.channel.epoll.EpollRecvByteAllocatorHandle
[WARNING]   io.netty.channel.epoll.EpollRecvByteAllocatorStreamingHandle
[WARNING]   io.netty.channel.epoll.EpollServerChannelConfig
[WARNING]   io.netty.channel.epoll.EpollServerDomainSocketChannel
[WARNING]   io.netty.channel.epoll.EpollServerSocketChannel
[WARNING]   io.netty.channel.epoll.EpollServerSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollSocketChannel
[WARNING]   io.netty.channel.epoll.EpollSocketChannelConfig
[WARNING]   io.netty.channel.epoll.EpollTcpInfo
[WARNING]   io.netty.channel.epoll.LinuxSocket
[WARNING]   io.netty.channel.epoll.Native
[WARNING]   io.netty.channel.epoll.NativeDatagramPacketArray
[WARNING]   io.netty.channel.epoll.NativeStaticallyReferencedJniMethods
[WARNING]   io.netty.channel.epoll.SegmentedDatagramPacket
[WARNING]   io.netty.channel.epoll.TcpMd5Util
[WARNING] Found duplicate classes/resources in runtime classpath.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.722 s
[INFO] Finished at: 2021-10-28T09:05:33+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.basepom.maven:duplicate-finder-maven-plugin:1.3.0:check (default) on project netty-all: Found duplicate classes/resources! -> [Help 1]