Interop with Scala jar

[CeylonMigrationBot]

[@FroMage] Trying Apache Spark leads to exceptions in the model loader, such as an NPE when completing packages which have a class named package (Scala has those, and package$ too), or completion failures for SparkContext$1.

[Migrated from ceylon/ceylon-compiler#2298] [Closed at 2015-10-06 12:50:21]

[CeylonMigrationBot]

[@FroMage] So apparently other problems:

• There are anonymous classes that javac treats as inner classes, for some reason
• There are local classes that javac treats as inner classes because of a Scala bug, I think: https://issues.scala-lang.org/browse/SI-9465
• There must be some "implicit" import of the Scala runtime, which we don't follow, which causes lots of:

/home/stephane/.m2/repository/org/apache/spark/spark-core_2.10/1.2.1/spark-core_2.10-1.2.1.jar(org/apache/spark/Accumulable.class): warning: Cannot find annotation method 'bytes()' in type 'ScalaSignature'

• Same reason, but we throw:

test/src/com/redhat/ceylon/compiler/java/test/cmr/modules/apachespark/test.ceylon:23: error: the 'ExpressionVisitor' caused an exception visiting a 'InvocationExpression' node: '"com.sun.tools.javac.code.Symbol$CompletionFailure: class file for scala.collection.Seq not found"'
    SparkConf conf = SparkConf();
                     ^

[CeylonMigrationBot]

[@FroMage] So this is fixed in master, where you just have to add a dependency on scala in your module:

module com.redhat.ceylon.compiler.java.test.cmr.modules.apachespark "1" {
    import "org.apache.spark:spark-core_2.10" "1.2.1";
    import "org.scala-lang:scala-library" "2.10.4";
    import java.base "7";
}

Then you can use Spark as such:

import java.lang { JString = String, JBoolean = Boolean }
import org.apache.spark { ... }
import org.apache.spark.api.java { ... }
import org.apache.spark.api.java.\ifunction { ... }

shared void run() {
    SparkConf conf = SparkConf().setMaster("local").setAppName("My App");
    JavaSparkContext sc = JavaSparkContext(conf);
    value textFile = sc.textFile("README.md");
    print(textFile.count());
    print(textFile.first());
    // How many lines contain "Ceylon"?
    print(textFile.filter(object satisfies Function<JString,JBoolean> {
            call(JString line) => JBoolean(line.contains(JString("Ceylon")));
        }).count());
}

For runtime, it's easier to run with ceylon run --flat-classpath --maven-overrides overrides.xml with this overrides file:

<overrides>
 <!-- Otherwise some artifact tries to use 1.1.0 which does not exist -->
 <set groupId="org.jboss.weld" artifactId="weld-osgi-bundle" version="1.1.4.Final"/>

 <!-- Otherwise some artifact tries to use a version with a missing method definition (old?) -->
 <set groupId="xerces" artifactId="xercesImpl" version="2.11.0"/>

 <!-- Otherwise we have two artifacts with the same contents, they got renamed -->
 <replace groupId="org.jboss.netty" artifactId="netty">
    <with groupId="io.netty" artifactId="netty" version="3.5.13.Final"/>
 </replace> 

</overrides>

[CeylonMigrationBot]

[@gavinking] Great work, Stef!

[CeylonMigrationBot]

[@FroMage] For 1.1 you don't have --flat-classpath so you are going to need a much bigger module override. I'll work on this. You also have to avoid wildcard imports in Scala libs, like import org.apache.spark { ... } and you have to specify the classes manually, otherwise it triggers a javac bug due to bogus Scala class files (that I work around in 1.2).