The problem

 

Yesterday, I downloaded the Forge 7.8.1.738 source for Minecraft 1.5.2. install.sh failed trying to access scala-library.jar with this error:

 

scala-library.jar; cannot read zip file

 

I was able to resolve the error, and I'm posting my fix for others who have the same problem.

 

Why the problem occurs

 

Here's my diagnosis of the underlying issue. The install script downloads a number of .jar files. When it tries to download scala-library.jar, the server returns a 404 page. But, the script doesn't detect this, and instead saves the HTML of the 404 page into scala-library.jar. Later, when something tries to read the .jar file as if it's a Java archive, it crashes, because the file contains HTML instead of valid .jar data. That's why it says "cannot read zip file." (Java archives are encoded in zip format.)

 

The solution

 

You need to give Forge a valid copy of scala-library.jar. I was able to obtain a copy from here:

 

http://www.scala-lang.org/download/

 

Download the main Scala package from that page. Extract the archive and look in the lib subfolder. You should see scala-library.jar there. Be sure you get a version of Scala that's compatible with Forge. As of this writing, that's Scala 2.10.2. Later versions may work, but I can't promise that.

 

Start with a freshly extracted copy of Forge. Run install.sh and let it fail. Copy your valid version of scala-library.jar (the one you got from scala-lang.org) into forge/mcp/lib, replacing the invalid version. Run install.sh again. It will ask you if you want to overwrite MCP. Say yes.

 

For me, that resolved the issue, and install.sh succeeded.

 

As a side note, the EAC mentions that you can download the .jars from forgeessentials.com. I tried this first, but the scala-library.jar from there appeared to be corrupted. I didn't spend much time investigating this error, because I was able to work around it by just downloading the file from scala-lang.org.

Thank you very much for this post, I almost gave up.

 

 

One thing I noticed is that there's a bit of a gap in between when the installer downloads scala-library.jar and when it extracts it, so if you're quick you can just paste the new one right over the broken one and the installer will run all the way through.

 

Thanks again!

Very helpful for those of us backporting our mods.