Add experimental support for Java 14 class files

[Godin]

No description provided.

[Godin]

Unlike how it was before thanks to #829, JaCoCo agent version 0.8.4 already successfully starts under Java 14 and can be used for earlier class file versions:

$ mkdir src

$ cat <<END > src/Example.java
class Example {
  public static void main(String[] args) {
    System.out.println("Hello, Java 14!");
  }
}
END

$ java -version
openjdk version "14-ea" 2020-03-17
OpenJDK Runtime Environment (build 14-ea+1-1)
OpenJDK 64-Bit Server VM (build 14-ea+1-1, mixed mode, sharing)

$ javac --release 13 src/Example.java -d classes

$ javap -v -p classes/Example.class | grep major
  major version: 57

$ java -javaagent:jacoco-0.8.4/lib/jacocoagent.jar=append=false -cp classes Example
Hello, Java 14!

$ java -jar jacoco-0.8.4/lib/jacococli.jar execinfo jacoco.exec
[INFO] Loading exec file jacoco.exec.
CLASS ID         HITS/PROBES   CLASS NAME
Session "Godins-iMac.lrc.sonarsource.com-44315859": Tue Jun 18 12:39:41 CEST 2019 - Tue Jun 18 12:39:41 CEST 2019
8ef792bffeab5d18    1 of   2   Example

Instrumentation of Java 14 class files requires this change:

$ javac --release 14 src/Example.java -d classes

$ javap -v -p classes/Example.class | grep major
  major version: 58

$ java -javaagent:jacoco-0.8.4/lib/jacocoagent.jar=append=false -cp classes Example
java.lang.instrument.IllegalClassFormatException: Error while instrumenting Example.
        at org.jacoco.agent.rt.internal_035b120.CoverageTransformer.transform(CoverageTransformer.java:93)
        at java.instrument/java.lang.instrument.ClassFileTransformer.transform(ClassFileTransformer.java:246)
        at java.instrument/sun.instrument.TransformerManager.transform(TransformerManager.java:188)
        at java.instrument/sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:563)
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:151)
        at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:823)
        at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:721)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:644)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:602)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
        at java.base/java.lang.Class.forName0(Native Method)
        at java.base/java.lang.Class.forName(Class.java:416)
        at java.base/sun.launcher.LauncherHelper.loadMainClass(LauncherHelper.java:760)
        at java.base/sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:655)
Caused by: java.io.IOException: Error while instrumenting Example.
        at org.jacoco.agent.rt.internal_035b120.core.instr.Instrumenter.instrumentError(Instrumenter.java:158)
        at org.jacoco.agent.rt.internal_035b120.core.instr.Instrumenter.instrument(Instrumenter.java:108)
        at org.jacoco.agent.rt.internal_035b120.CoverageTransformer.transform(CoverageTransformer.java:91)
        ... 16 more
Caused by: java.lang.IllegalArgumentException: Unsupported class file major version 58
        at org.jacoco.agent.rt.internal_035b120.asm.ClassReader.<init>(ClassReader.java:195)
        at org.jacoco.agent.rt.internal_035b120.asm.ClassReader.<init>(ClassReader.java:176)
        at org.jacoco.agent.rt.internal_035b120.asm.ClassReader.<init>(ClassReader.java:162)
        at org.jacoco.agent.rt.internal_035b120.core.internal.instr.InstrSupport.classReaderFor(InstrSupport.java:279)
        at org.jacoco.agent.rt.internal_035b120.core.instr.Instrumenter.instrument(Instrumenter.java:74)
        at org.jacoco.agent.rt.internal_035b120.core.instr.Instrumenter.instrument(Instrumenter.java:106)
        ... 17 more
Hello, Java 14!

$ java -jar jacoco-0.8.4/lib/jacococli.jar execinfo jacoco.exec
[INFO] Loading exec file jacoco.exec.
CLASS ID         HITS/PROBES   CLASS NAME
Session "Godins-iMac.lrc.sonarsource.com-131a0b": Tue Jun 18 12:42:31 CEST 2019 - Tue Jun 18 12:42:31 CEST 2019

Here is end-to-end test after this change:

$ javac --release 14 src/Example.java -d classes

$ javap -v -p classes/Example.class | grep major
  major version: 58

$ java -javaagent:jacoco-0.8.5.201906181015/lib/jacocoagent.jar=append=false -cp classes Example
Hello, Java 14!

$ java -jar jacoco-0.8.5.201906181015/lib/jacococli.jar classinfo classes/Example.class
  INST   BRAN   LINE   METH   CXTY   ELEMENT
     7      0      3      2      2   class 0x1fe8c4cca7e8812a Example

$ java -jar jacoco-0.8.5.201906181015/lib/jacococli.jar instrument classes --dest instrumented
[INFO] 1 classes instrumented to /private/tmp/example/instrumented.

$ javap -v -p instrumented/Example.class | grep major
  major version: 58

$ java -cp instrumented:jacoco-0.8.5.201906181015/lib/jacocoagent.jar Example
Hello, Java 14!

$ java -jar jacoco-0.8.5.201906181015/lib/jacococli.jar execinfo jacoco.exec
[INFO] Loading exec file jacoco.exec.
CLASS ID         HITS/PROBES   CLASS NAME
Session "Godins-iMac.lrc.sonarsource.com-c4b4e5b": Tue Jun 18 12:17:52 CEST 2019 - Tue Jun 18 12:17:53 CEST 2019
1fe8c4cca7e8812a    1 of   2   Example
Session "Godins-iMac.lrc.sonarsource.com-6c28ab93": Tue Jun 18 12:18:56 CEST 2019 - Tue Jun 18 12:18:56 CEST 2019
1fe8c4cca7e8812a    1 of   2   Example

$ java -jar jacoco-0.8.5.201906181015/lib/jacococli.jar report jacoco.exec --classfiles classes
[INFO] Loading execution data file /private/tmp/example/jacoco.exec.
[INFO] Analyzing 1 classes.

[Godin]

@marchof can we merge this? 😉

[marchof]

@Godin Sure! Sorry, got stuck in my inbox...

[Godin]

@marchof wow, that was fast 😆