The simple solution of just slapping in some random name (`io.netty.all`) is that this will cause the packages within this jar to be exported from more than one Java Module, and that will also cause problems.

The other fix is to remove the attribute from the manifest entirely. Netty-all is a pom-only dependency now, so it doesn't have any packages in the jar file. Still, it _probably_ shouldn't try to declare any automatic module name.
wouldn't it be better to not define a module at all if it not ships any classes ? 

/cc @shs96c As long as this jar doesn't contain any classes, it'll be fine. The problems with the module system start when the same class is present in two or more jars: split packages (and therefore duplicate classes) are strictly forbidden. ok then it is fine.. Thanks! > wouldn't it be better to not define a module at all if it not ships any classes ?

Like I said above, I tried to make that happen, couldn't get it to work.
`io.netty:netty-all:4.1.75.Final` declares an empty automatic module name
### Expected behavior

If the `Automatic-Module-Name` manifest property is present, it should be set to a meaningful value. This attribute is defined in the manifest for `io.netty:netty-all:4.1.75.Final`

### Actual behavior

In `io.netty:netty-all:4.1.75.Final` (and earlier versions), this is declared but not set. This causes any toolchain that attempts to use java modules to get upset.

### Steps to reproduce

```shell
jar xvf ~/Downloads/netty-all-4.1.75.Final.jar META-INF/MANIFEST.MF
head META-INF/MANIFEST.MF
```

The output is:

```
Manifest-Version: 1.0
Implementation-Title: Netty/All-in-One
Bundle-Description: Netty is an asynchronous event-driven network appl
 ication framework for    rapid development of maintainable high perfo
 rmance protocol servers and    clients.
Automatic-Module-Name: 
Bundle-License: https://www.apache.org/licenses/LICENSE-2.0
Bundle-SymbolicName: io.netty.all
Implementation-Version: 4.1.75.Final
Built-By: norman
```

The problematic thing is that `Automatic-Module-Name` is declared but not set.

### Netty version

4.1.75.Final

### JVM version (e.g. `java -version`)

9+

all/pom.xml
all/pom.xml
diff --git a/all/pom.xml b/all/pom.xml
index 7dcd227bd84..1265fe3d3de 100644
--- a/all/pom.xml
+++ b/all/pom.xml
@@ -29,6 +29,7 @@
   <name>Netty/All-in-One</name>
 
   <properties>
+    <javaModuleName>io.netty.all</javaModuleName>
     <generatedSourceDir>${project.build.directory}/src</generatedSourceDir>
     <dependencyVersionsDir>${project.build.directory}/versions</dependencyVersionsDir>
     <japicmp.skip>true</japicmp.skip>
