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Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711246]

Wed, 14 October 2015 09:43

Sergey Toshin

Messages: 56
Registered: May 2015

Member

Hi,
I have a code that removes all complex (not SimpleName expressions) from ifs. It works fine and the code like

if(obj.getSomeInt() > 10)
{
/* body */
}

is converted to

boolean value = obj.getSomeInt() > 10;
if(value)
{
/* body */
}

But before changing AST the call to resolveBinding() and resolveTypeBinding() for obj gives correct results, but after I get null for the both calls. Is that as designed? If yes, please tell how to fix that?

My code:

if(node instanceof IfStatement)
{
	IfStatement stmt = (IfStatement) node;
	AST ast = node.getAST();
	Expression expr = stmt.getExpression();
	if(!(expr instanceof SimpleName))
	{
		SimpleName varName = ast.newSimpleName(generateVariableName());
		
		VariableDeclarationFragment vdf = ast.newVariableDeclarationFragment();
		vdf.setName((SimpleName) ASTNode.copySubtree(ast, varName));
		vdf.setInitializer((Expression) ASTNode.copySubtree(ast, expr));
		
		VariableDeclarationStatement vds = ast.newVariableDeclarationStatement(vdf);
		vds.setType(resolveType(e));
		list.add(i++, vds);
		
		stmt.setExpression(varName);
	}
}

Before this operation, all bindings from expr are lost

[Updated on: Wed, 14 October 2015 10:35]

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711265 is a reply to message #1711246]

Wed, 14 October 2015 13:06

Erick Hagstrom

Messages: 107
Registered: April 2014
Location: USA

Senior Member

Yes, this is as designed. Per the Eclipse documentation (JDT Plug-in Developer Guide > Programmer's Guide > JDT Core), "As soon as the tree has been modified, all positions and bindings are lost."

The thing is, there is no way in general to tell what obj is once the tree has been changed. The bindings have to be invalidated on any change.

To fix it, you'd need to apply your changes and get a new AST.

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711361 is a reply to message #1711265]

Thu, 15 October 2015 10:15

Sergey Toshin

Messages: 56
Registered: May 2015

Member

How to generate new AST if I have edited AST?

Is that possible to keep old ASTNodes positions? When I add a new node, it has -1 start position and 0 length, it's important to make changes and have old position numbers. But I believe after changing the AST it won't be possible. Maybe there is another way to implement this feature?
The most obvious way I see is running ASTVisitor for ASTNode on old AST, collecting all ASTNodes and then running it for new AST with appending found nodes (they should be the same and have the same positions). Later to get old position, I can call hashMap.get(newNode).getStartPosition. But maybe there is a better way? Thanks

[Updated on: Thu, 15 October 2015 10:17]

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711880 is a reply to message #1711361]

Tue, 20 October 2015 08:55

Sergey Toshin

Messages: 56
Registered: May 2015

Member

Any ideas?

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711881 is a reply to message #1711361]

Tue, 20 October 2015 08:56

Sergey Toshin

Messages: 56
Registered: May 2015

Member

Any ideas?

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1711945 is a reply to message #1711881]

Tue, 20 October 2015 11:45

Erick Hagstrom

Messages: 107
Registered: April 2014
Location: USA

Senior Member

Take a look at Eclipse Documentation: JDT Plug-in Developer Guide > Programmer's Guide > JDT Core > Manipulating Java code. (At least that's where it is in my Luna installation. Your Mars-ilage may vary.) There's a section about 40% down called Creating an AST by reconciling a working copy. You may get some ideas there.

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1713740 is a reply to message #1711945]

Fri, 06 November 2015 11:06

Sergey Toshin

Messages: 56
Registered: May 2015

Member

I've looked, but I have no idea how to point my CompilationUnit in recouncile method.
My code:

:
:
CompilationUnit cu = (CompilationUnit) parser.createAST(null);
:
:
//changes to AST
:
:
	    
IWorkspace workspace = ResourcesPlugin.getWorkspace();
IPath path = Path.fromOSString(MY_SOURCE_FILE.getAbsolutePath());
IFile file = workspace.getRoot().getFileForLocation(path);
ICompilationUnit compilationUnit = (ICompilationUnit) JavaCore.create(file);
compilationUnit.reconcile(AST.JLS8, true, true, workingCopyOwner (???), iProgressMonitor (???) );

Can you please help me with that? Thanks

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Re: Bindings are lost after copying subtree with ASTNode.copySubtree(...) [message #1714301 is a reply to message #1713740]

Wed, 11 November 2015 15:26

Sergey Toshin

Messages: 56
Registered: May 2015

Member

So my general point is to 1) save original positions in the modified code (so, I'm not satisfied when I make changes and bindins are missed, but other things are perfect: old positions are saved, created elements have -1 position); 2) save bindings. I feel that when I do rewrite, I will lose old code elements positions, but it's not allowed

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