jigsaw: cannot find Kotlin symbols

Question

I have a Java/Kotlin project with multiple sub-projects (modules). This is module-info.java for the base module:

module ir.openuniverse {
    requires java.desktop;
    requires kotlin.stdlib;
    requires transitive org.apache.logging.log4j;
    requires org.apache.logging.log4j.core;

    exports ir.openuniverse;  // Base module has exported here.
}

And for a consumer module, I have:

module ir.openuniverse.watchservice {
    requires kotlin.stdlib;
    requires gson;
    requires ir.openuniverse; // Base module has imported here

    exports ir.openuniverse.watchservice;
}

Now I insert a test file in consumer module:

package ir.openuniverse.watchservice;

import ir.openuniverse.UtilKt;
import ir.openuniverse.JUtil;
import ir.openuniverse.Entry; 

public class Test {}

and then try to compile it:

> Task :watch-service:compileJava FAILED
[...]\watch-service\src\main\ir\openuniverse\watchservice\Test.java:3: error: cannot find symbol
import ir.openuniverse.UtilKt;
                      ^
  symbol:   class UtilKt
  location: package ir.openuniverse
[...]\watch-service\src\main\ir\openuniverse\watchservice\Test.java:5: error: cannot find symbol
import ir.openuniverse.Entry;
                      ^
  symbol:   class Entry
  location: package ir.openuniverse
2 errors

FAILURE: Build failed with an exception.

^{All three classes (UtilKt, JUtil, Entry) are in the base module. But JUtil is in Java (JUtil.java) and two others in Kotlin (Util.kt and Entry.kt).}

As you can see there is no problem with importing JUtil, but the classes that their sources in Kotlin, can't be resolved. (Without importing two Kotlin classes I can compile the module, successfully).

Also, there is no problem if I don't use Java 9 module system totally.

I use Gradle and tested with these two plugins:

gradle.plugin.org.gradle.java:experimental-jigsaw:0.1.1

xor:

gradle.plugin.rgoldberg:experimental-jigsaw:0.4.1-SNAPSHOT

UPDATE 1:

Due to @nullpointer's comment, I tried to check classpaths. This is a part of executing the task with --debug option that shows -classpath is empty and --module-path has correct values (Especially see these two: D:\Devel\IdeaProjects\Tinifier\base\build\classes\java\main;D:\Devel\IdeaProjects\Tinifier\base\build\classes\kotlin\main;):

05:40:29.575 [DEBUG] [org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler] Compiler arguments: -source 11 -target 11 -d D:\Devel\IdeaProjects\Tinifier\watch-service\build\classes\java\main -g -sourcepath  -proc:none -XDuseUnsharedTable=true -classpath  --module-path D:\Devel\.gradle\caches\modules-2\files-2.1\org.jetbrains.kotlin\kotlin-stdlib-jdk8\1.3.10\71d0fa967493eb76648b575edf1762cb2d0c7f10\kotlin-stdlib-jdk8-1.3.10.jar;D:\Devel\.gradle\caches\modules-2\files-2.1\com.google.code.gson\gson\2.8.5\f645ed69d595b24d4cf8b3fbb64cc505bede8829\gson-2.8.5.jar;D:\Devel\IdeaProjects\Tinifier\base\build\classes\java\main;D:\Devel\IdeaProjects\Tinifier\base\build\classes\kotlin\main;D:\Devel\.gradle\caches\modules-2\files-2.1\org.jetbrains.kotlin\kotlin-stdlib-jdk7\1.3.10\4d147bf43060dc43d61b096e24da1e67dfe0c032\kotlin-stdlib-jdk7-1.3.10.jar;D:\Devel\.gradle\caches\modules-2\files-2.1\org.jetbrains.kotlin\kotlin-stdlib\1.3.10\b178c1501609c6e4ee8be635513cb023a466457d\kotlin-stdlib-1.3.10.jar;D:\Devel\.gradle\caches\modules-2\files-2.1\org.apache.logging.log4j\log4j-api\2.11.1\268f0fe4df3eefe052b57c87ec48517d64fb2a10\log4j-api-2.11.1.jar;D:\Devel\.gradle\caches\modules-2\files-2.1\org.jetbrains.kotlin\kotlin-stdlib-common\1.3.10\1b19d99229dcedad7caf50534dce38fe82845269\kotlin-stdlib-common-1.3.10.jar;D:\Devel\.gradle\caches\modules-2\files-2.1\org.jetbrains\annotations\13.0\919f0dfe192fb4e063e7dacadee7f8bb9a2672a9\annotations-13.0.jar;D:\Devel\IdeaProjects\Tinifier\watch-service\build\classes\kotlin\main D:\Devel\IdeaProjects\Tinifier\watch-service\src\main\ir\openuniverse\watchservice\T.java D:\Devel\IdeaProjects\Tinifier\watch-service\src\main\module-info.java
05:40:29.576 [INFO] [org.gradle.api.internal.tasks.compile.JdkJavaCompiler] Compiling with JDK Java compiler API.
05:40:30.138 [ERROR] [system.err] D:\Devel\IdeaProjects\Tinifier\watch-service\src\main\ir\openuniverse\watchservice\T.java:3: error: cannot find symbol
05:40:30.139 [ERROR] [system.err] import ir.openuniverse.UtilKt;
05:40:30.139 [ERROR] [system.err]                       ^
05:40:30.139 [ERROR] [system.err]   symbol:   class UtilKt
05:40:30.139 [ERROR] [system.err]   location: package ir.openuniverse
05:40:30.142 [ERROR] [system.err] D:\Devel\IdeaProjects\Tinifier\watch-service\src\main\ir\openuniverse\watchservice\T.java:5: error: cannot find symbol
05:40:30.142 [ERROR] [system.err] import ir.openuniverse.Entry;
05:40:30.143 [ERROR] [system.err]                       ^
05:40:30.143 [ERROR] [system.err]   symbol:   class Entry
05:40:30.143 [ERROR] [system.err]   location: package ir.openuniverse
05:40:30.164 [ERROR] [system.err] 2 errors

Unfortunately, even though I know Compiler arguments from above logs, I don't know how to manually compile the source. Simply running javac doesn't work.

UPDATE 2:

Making a copy of Kotlin .class files to the path of Java .class files solved the issue. See my answer for a simple Gradle's configuration to do this. But I know this is not a fundamental solution.

UPDATE 3:

I found a more fundamental issue! If I remove all Java sources from a module (even if it's not depended on another; like my base module) and just stay Kotlin sources, then the compilation of that module throws at where that package (that includes only Kotlin sources) exported (in module-info.java) and says the package is empty!!:

> Task :base:compileJava FAILED
D:\Devel\IdeaProjects\Tinifier\base\src\main\module-info.java:9: error: package is empty or does not exist: ir.openuniverse
    exports ir.openuniverse;
              ^
1 error

FAILURE: Build failed with an exception.

user_5318303 · Answer

Making a copy of Kotlin .class files to the path of Java .class files solved the issue. But I know this is not a fundamental solution (As a sample see UPDATE 3 of the question). You can change the destination path of the Kotlin compilation. In Gradle:

sourceSets {
    main {
        // Optional: Removing `java` directory from output path that usually is `build/classes/java/main/`:  
        java.outputDir = file(java.outputDir.toString().replaceAll("\${File.separatorChar}java", ""))

        // Mandatory:
        kotlin.outputDir = java.outputDir 
    }
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"

    // Unfortunately setting `main.kotlin.outputDir` isn't enough. See: https://stackoverflow.com/questions/49638136/kotlin-gradle-plugin-how-to-use-custom-output-directory#comment95108749_49638136 and https://youtrack.jetbrains.com/issue/KT-23807
    destinationDir = sourceSets.main.kotlin.outputDir
}

compileTestKotlin {
    // ...
}

jigsaw: cannot find Kotlin symbols

1 Answers