如何进行AST转换？

Question

I'm trying to run the AST transformation from this example:

http://melix.github.io/ast-workshop/exercise1-hints.html

But when I run the test I get my assertions failed.

I need to compile class AuthorAdderASTTransformation first? I even did that too, added a main method and compiled it. But still test fails saying:

groovy.lang.MissingPropertyException: No such property: $AUTHOR for class: org.gr8conf.AuthorAdderASTTransformationTest
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:50)
    at org.codehaus.groovy.runtime.callsite.GetEffectivePogoPropertySite.getProperty(GetEffectivePogoPropertySite.java:86)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:231)
    at org.gr8conf.AuthorAdderASTTransformationTest.testThatAuthorExists(AuthorAdderASTTransformationTest.groovy:5)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:202)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)


groovy.lang.MissingPropertyException: No such property: $AUTHOR for class: Foo
    at groovy.lang.MetaClassImpl.invokeStaticMissingProperty(MetaClassImpl.java:900)
    at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:1729)
    at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:1705)
    at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:3458)
    at org.codehaus.groovy.runtime.callsite.ClassMetaClassGetPropertySite.getProperty(ClassMetaClassGetPropertySite.java:48)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:227)
    at TestScripttestASTTransformationShouldBeDebuggableFromIDE0.run(TestScripttestASTTransformationShouldBeDebuggableFromIDE0.groovy:4)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:518)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:556)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:537)
    at groovy.util.GroovyTestCase.assertScript(GroovyTestCase.java:203)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:272)
    at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
    at org.gr8conf.AuthorAdderASTTransformationTest.testASTTransformationShouldBeDebuggableFromIDE(AuthorAdderASTTransformationTest.groovy:9)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:202)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

where I'm making the mistake?

Answer 1

The exception says that your test tried to read the property $AUTHOR, but it was not found. Assuming the transform itself is right, and that you actually ask the right class, it means it was not run. I can only assume these two points, since you didn't give any information on that.

So then onto why it was not run. AuthorAdderASTTransformation needs to be precompiled when you compile Foo. But even that is not enough, there needs to be metadata for it as well. The page http://www.groovy-lang.org/metaprogramming.html#developing-ast-xforms suggest creating a jar for it. While that is not strictly required it well prevent you forgetting the meta data file services correctly when compiling your normal source code.