What version of Java compiler does SBT use? Super strange compiler errors

[benmccann]

Hi,

I'm trying to compile Google Guava with SBT and am getting some exceedingly strange errors.  It compiles fine with Maven, but SBT does not like it at all:

[error] Maps.java:517: incompatible types; no instance(s) of type variable(s) K,V exist so that java.util.TreeMap<K,V> conforms to java.util.SortedMap<K,V>

[error] found   : <K,V>java.util.TreeMap<K,V>

[error] required: java.util.SortedMap<K,V>

[error]     SortedMap<K, V> onlyOnLeft = Maps.newTreeMap(comparator);

[error]                                                 ^

[error] Maps.java:518: incompatible types; no instance(s) of type variable(s) K,V exist so that java.util.TreeMap<K,V> conforms to java.util.SortedMap<K,V>

[error] found   : <K,V>java.util.TreeMap<K,V>

[error] required: java.util.SortedMap<K,V>

[error]     SortedMap<K, V> onlyOnRight = Maps.newTreeMap(comparator);

[error]                                                  ^

[error] Maps.java:520: incompatible types; no instance(s) of type variable(s) K,V exist so that java.util.TreeMap<K,V> conforms to java.util.SortedMap<K,V>

[error] found   : <K,V>java.util.TreeMap<K,V>

[error] required: java.util.SortedMap<K,V>

[error]     SortedMap<K, V> onBoth = Maps.newTreeMap(comparator);

[error]                                             ^

[error] Maps.java:522: incompatible types; no instance(s) of type variable(s) K,V exist so that java.util.TreeMap<K,V> conforms to java.util.SortedMap<K,com.google.common.collect.MapDifference.ValueDifference<V>>

[error] found   : <K,V>java.util.TreeMap<K,V>

[error] required: java.util.SortedMap<K,com.google.common.collect.MapDifference.ValueDifference<V>>

[error]         Maps.newTreeMap(comparator);

To reproduce run "git clone https://code.google.com/p/guava-libraries/" and then place this build.sbt in guava-libraries/guava/

Thanks,

Ben

[Paul Phillips]

On Thu, Apr 12, 2012 at 11:13 PM, benmccann <benjamin...@gmail.com> wrote:
> I'm trying to compile Google Guava with SBT and am getting some exceedingly
> strange errors.  It compiles fine with Maven, but SBT does not like it at
> all:

Your problem isn't sbt. I suspect something interesting on your classpath.

% sbt compile
Detected sbt version 0.11.2
Using /Users/paulp/.sbt/0.11.2 as sbt dir, -sbt-dir to override.
[info] Loading global plugins from /Users/paulp/.sbt/0.11.2/plugins
[info] Set current project to guava (in build file:/s/guava-libraries/guava/)
[info] Compiling 388 Java sources to
/s/guava-libraries/guava/target/scala-2.9.1/classes...
[success] Total time: 15 s, completed Apr 13, 2012 12:40:16 AM

[Ben McCann]

Hmm, strange, so you were able to compile Guava using my build script?  Shouldn't our classpaths be the same if we were using the same build script?  Any idea how I would print mine out to see if something strange were added?

Does SBT use the Java on your $PATH?  I have Oracle JDK 6 installed on Ubuntu 11.10.  What about you?

Thanks for helping me take a look at this!

-Ben

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[Brian Smith]

Seems to be an issue with certain versions of OpenJDK.

https://groups.google.com/forum/?fromgroups#!topic/guava-discuss/5eWXOmMINvc 

https://groups.google.com/forum/#!msg/guava-discuss/dKj4jfsLDgA/Jb3_TepKmc8J

https://bugs.openjdk.java.net/show_bug.cgi?id=100167

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[Ben McCann]

Hmm, I'm running the Oracle version of Java.  I do have OpenJDK installed, but it's not the default one on my path.  Is SBT perhaps somehow picking it up anyway?

$ java -version

java version "1.6.0_31"

Java(TM) SE Runtime Environment (build 1.6.0_31-b04)

Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01, mixed mode)

[Ben McCann]

Ooh, actually, I only had the Oracle version of java and not javac, so that might be it.

[Ben McCann]

Yep, so SBT uses the javac that is on your path and this was a bug with OpenJDK.  I wrote up some instructions on how to install Oracle JDK.  I followed someone else's originally and they had a poor usage of update-alternatives which changed only my java version and not my javac version, which led to some confusion as well.

http://www.benmccann.com/dev-blog/installing-oracle-java-jdk-on-ubuntu/ 

Thanks so much for the help on this!

[Mark Harrah]

On Thu, 12 Apr 2012 21:08:14 -0700
Ben McCann <b...@benmccann.com> wrote:

> Yep, so SBT uses the javac that is on your path and this was a bug with
> OpenJDK. I wrote up some instructions on how to install Oracle JDK. I
> followed someone else's originally and they had a poor usage of
> update-alternatives which changed only my java version and not my javac
> version, which led to some confusion as well.
> http://www.benmccann.com/dev-blog/installing-oracle-java-jdk-on-ubuntu/

Note that you can control the version of Java used with javaHome:

javaHome := Some(file("/path/to/java/home"))

If you put this in ~/.sbt/global.sbt, it should take effect for all of your projects and plugins built on your machine without having to publish it as part of your build (where it won't work for others).

-Mark