Warn when certain constructor is used

[Pietro Paolini]

Hi Maurizio,

I got stuck but I feel I am not that far from it, I have taken bits and pieces from here http://scg.unibe.ch/archive/projects/Erni08b.pdf - that is somewhat different from 
What I want to do, namely it wants to re-write part of the AST while I just want to scan it to print some diagnostic info.

I realize my usages of the term  AST may be improper, is that the *actual* AST the parser generated ? 

@SupportedAnnotationTypes("*")
    class LocalDateUtilDate extends TreeScanner {

        @Override
        public Object visitNewClass(NewClassTree newClassTree, Object o) {
            processingEnvironment.getMessager().printMessage(Diagnostic.Kind.WARNING, "You should not be using ...");
            return super.visitNewClass(newClassTree, o);
        }
    }


@Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {

        if (!roundEnv.processingOver()) {
            Set<? extends Element> elements = roundEnv.getRootElements();
            for (Element element : elements) {
                if (element.getKind() == ElementKind.CLASS) {
                    JCTree tree = (JCTree) trees.getTree(element);
                    tree.accept(new LocalDateUtilDate());
                }

                System.out.println(element);
            }
        }
        return false;
    }

JCTree tree = (JCTree) trees.getTree(element);
tree.accept(new LocalDateUtilDate());

This bit does not compile as I am probably using the API badly,  what do I need to do to get my scanner "scanning" :-) ?

Thanks,
P.
> -----Original Message-----
> From: Maurizio Cimadamore [mailto:maurizio.cimadamore at oracle.com]
> Sent: 31 May 2018 11:32
> To: Pietro Paolini; compiler-dev at openjdk.java.net
> Subject: Re: Warn when certain constructor is used
> 
> Hi Pietro,
> I believe the compiler tree API is what you want (I'm giving you JDK 7
> API links, since your link seems to be referring to JDK 7, but these API
> points are available in later releases as well, of course):
> 
> https://docs.oracle.com/javase/7/docs/jdk/api/javac/tree/index.html
> 
> More specifically, if you are writing an annotation processor, the
> compiler tree API allows you to retrieve a Tree objects for a given Element:
> 
> https://docs.oracle.com/javase/7/docs/jdk/api/javac/tree/com/sun/source/ut
> il/Trees.html
> 
> After which, you can define a visitor which detects the constructor
> calls you are interested in. For the visitor look here:
> 
> https://docs.oracle.com/javase/7/docs/jdk/api/javac/tree/com/sun/source/ut
> il/TreeScanner.html
> 
> there's a scan method for every tree node, I think you want to override
> visitNewClass:
> 
> https://docs.oracle.com/javase/7/docs/jdk/api/javac/tree/com/sun/source/ut
> il/TreeScanner.html#visitNewClass(com.sun.source.tree.NewClassTree,%20P)
> 
> As for generating diagnostics, you can do that by using the Messager
> interface which is part of the annotation processing API:
> 
> https://docs.oracle.com/javase/7/docs/api/javax/annotation/processing/Mes
> sager.html
> 
> you obtain one of these from the ProcessingEnvironment object you get at
> the start of anno processing - see
> 
> https://docs.oracle.com/javase/7/docs/api/javax/annotation/processing/Proc
> essor.html#init(javax.annotation.processing.ProcessingEnvironment)
> 
> 
> I think these pointers should be enough to get started, feel free to
> reach out if you get stuck.
> 
> Maurizio
> 
> 
> On 31/05/18 10:05, Pietro Paolini wrote:
> > Hi all,
> >
> > I am not sure the question is appropriate for compiler-dev but I would like
> to give it a try anyway.
> >
> > I would like to detect when a certain class's constructor is used and log its
> usage along with filename and line number somewhere, such as a log file or
> standard output, I can't use an IDE to do that as I am working on a fairly large
> codebase and I need to automate the process, moreover it seems like an
> interesting problem to solve.
> >
> > https://docs.oracle.com/javase/7/docs/api/javax/tools/JavaCompiler.html
> >
> > I was hoping that could help me but I haven't spot anything as yet, even
> though I must admit that my knowledge on the matter is limited.
> >
> > Thanks,
> > Pietro
> >
> >
> > Pietro Paolini
> > Consultant
> >
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