How to add an annotation and import to a Java class

Thanks for the advice. I have replaced my code with:

PsiModifierList classModifierList = psiClass.getModifierList();
PsiAnnotation entityAnnotation = classModifierList.addAnnotation("javax.persistence.Entity");
javaCodeStyleManager.shortenClassReferences(entityAnnotation);

When I run my unit test, the annotation is added at the correct place (no line of whitespace) but it still has a fully qualified class name. I've also tried calling shortenClassReferences on the psiJavaFile object, but that doesn't help either. Any ideas?

Please show the full method/context of this code.

Here is the section adding the annotation:

PsiClass psiClass = javaPsiFacade.findClass(className, GlobalSearchScope.projectScope(project));
log("Found class: " + psiClass);

// want to add @Entity annotation after import list, before class declaration
PsiJavaFile psiJavaFile = (PsiJavaFile) psiClass.getContainingFile();

PsiModifierList classModifierList = psiClass.getModifierList();

ReadonlyStatusHandler.getInstance(project).ensureFilesWritable();

WriteCommandAction.runWriteCommandAction(project, () -> {

    PsiAnnotation entityAnnotation = classModifierList.addAnnotation("javax.persistence.Entity");

    log("Reformatting file");
    // shortenClassReferences takes the fully qualified class name used in the annotation and shortens it, adding the import
    javaCodeStyleManager.shortenClassReferences(entityAnnotation);
    javaCodeStyleManager.shortenClassReferences(psiJavaFile);
    codeStyleManager.reformat(psiJavaFile);

});

The code is inside an Action. i.e. extends AnAction and called from the actionPerformed method. 

At the moment I'm running it from a test, which extends

LightCodeInsightFixtureTestCase

I then create a new instance of the action, and call:

myFixture.testAction(myActionInstance)

Is the annotation class "javax.persistence.Entity" made available in test (e.g. added as "fake" or library added to ProjectDescriptor)?

Ahh..this will be the step I'm missing. Looking at the IntelliJ notes here:

https://www.jetbrains.org/intellij/sdk/docs/basics/testing_plugins/light_and_heavy_tests.html

It looks like I need to override the method to return the project descriptor:

protected LightProjectDescriptor getProjectDescriptor() 

How do I add a library into the project descriptor?

Thanks.

Override com.intellij.testFramework.fixtures.DefaultLightProjectDescriptor#configureModule and use PsiTestUtil#add(Project)Library

alternatively just add a (dummy version) of annotation via com.intellij.testFramework.fixtures.JavaCodeInsightTestFixture#addClass

Hmm. Still can't get this working. I've written a project descriptor like this:

public class HbmProjectDescriptor extends DefaultLightProjectDescriptor {

    @Override
    public void configureModule(@NotNull Module module, @NotNull ModifiableRootModel model, @NotNull ContentEntry contentEntry) {
        super.configureModule(module, model, contentEntry);
        String libPath = "/Users/proctorh/.m2/repository/org/hibernate/javax/persistence/hibernate-jpa-2.1-api/1.0.0.Final/hibernate-jpa-2.1-api-1.0.0.Final.jar";
        File testLib = new File(libPath);
        System.out.println("Does library exist? " + testLib.exists());
        PsiTestUtil.addLibrary(module, libPath);

        PsiTestUtil.addProjectLibrary(module, libPath);
    }
}

And then in my test class use this like this:

public class HbmToAnnotationsTest extends LightCodeInsightFixtureTestCase {

    @NotNull
    @Override
    protected LightProjectDescriptor getProjectDescriptor() {
        return new HbmProjectDescriptor();
    }

However the fully qualified annotation name is still not being shortened when I run the test. Am I missing something? Is there any debug checks / output I can put into the test to check it is being set up correctly? Thanks.

Apologies, the test is working correctly now with the above code. Many thanks for your help!

Actually, I should clarify. I didn't get this working by overriding the project descriptor. Even though I had print statements in the project descriptor showing that code was being invoked, it only worked when the code was in the test setup() method. 

i.e. test case extends LightCodeInsightFixtureTestCase and has the following:

@Override
protected void setUp() throws Exception {
    super.setUp();

    String libPath = "/Users/proctorh/.m2/repository/org/hibernate/javax/persistence/hibernate-jpa-2.1-api/1.0.0.Final/hibernate-jpa-2.1-api-1.0.0.Final.jar";
    File testLib = new File(libPath);
    System.out.println("Does library exist? " + testLib.exists());
    PsiTestUtil.addLibrary(myFixture.getModule(), libPath);

    PsiTestUtil.addProjectLibrary(myFixture.getModule(), libPath);
}

That's most likely incorrect, because the added library can leak into unrelated light tests with the same descriptor. I'd suggest to investigate why adding it in the descriptor isn't working. I'd do it by putting breakpoints into the place where the libraries are added in your derscriptor, check whether they're really added (i.e. the root model contains them after the descriptor finishes). Then I'd also check if there are other ProjectRootListener#rootsChanged events after that that remove the library for any reason.