Helping to find the usefulness of a proposal

[Jonathan Gibbons]

For all this sort of analysis, you'd do better to use the combination of 
javac's
annotation processing framework and the javac Tree API, than to use direct
access into private javac API.

Annotation processing isn't just for processing annotations ;-)  You can 
write
a processor that will be called on all types, and you can bridge from the
processing world (javax.lang.model.*) to the java Tree API 
(com.sun.source.*)
using com.sun.source.util.Trees.   This allows you to write utilities to
analyze ASTs without requiring the use of any javac internal API.

-- Jon



Mark Mahieu wrote:
> Wow.
>
> http://www.geekherocomic.com/comics-highres/2009-02-25-coding-overkill.png
>
>
> Here are the important bits from my quick hack.  Took under half an hour to
> get it finding cases where Auto-assignment Parameters would and wouldn't
> work across large source trees.
>
> Of course, javac makes much more than parsing available if you need it...
>
>
>
> import com.sun.tools.javac.file.JavacFileManager;
> import com.sun.tools.javac.parser.JavacParser;
> import com.sun.tools.javac.parser.ParserFactory;
> import com.sun.tools.javac.tree.TreeScanner;
> import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
> import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
> import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
> import com.sun.tools.javac.util.Context;
> import com.sun.tools.javac.util.List;
>
> ...
>
> // create a TreeScanner to do your analysis
> TreeScanner scanner = new TreeScanner() {
>
> @Override
> public void visitMethodDef(JCMethodDecl tree) {
>  // look at a method's parameters
> for (List<JCVariableDecl> l = params; l.nonEmpty(); l = l.tail) {
> JCVariableDecl param = l.head;
>  // examine param or whatever
> }
>  // continue recursively scanning the method body etc
> super.visitMethodDef(tree);
> }
> };
>
> ...
>
> Context context = new Context();
> JavacFileManager.preRegister(context);
> ParserFactory factory = ParserFactory.instance(context);
>
> String sourceCode = readSourceFromFile(...);
>
> JavacParser parser = (JavacParser) factory.newParser(sourceCode, false,
> false, false);
> JCCompilationUnit cu = parser.parseCompilationUnit();
>
> // do your analysis
> scanner.scan(cu);
>
>