Get list of accessible variables at point in code

[sourabhsparkala]

I am trying to ffind all the possible list of CtLocalVariable or CtField which are accessible depending on the position at a point in code. A small example is give below.

Is it possible to query for something like this in spoon?

package app;


public class App 
{
	
	static int test = 0;
	public static void main(String[] args)
	{
		int local = 0;  /* The iftest local variable from ifblock should not be accessible within this outer parentblock. similarly the variables "local" and "test" should be accessible within this block.*/
		System.out.println("Hello world");
		
		if(test<3){   /* The iftest local variable should be accessible within this ifblock, not outside. similarly the variables "local" and "test" should be accessible within this block as well.*/
			
			int iftest = 10;
			test += 1;
		}
		 /* The iftest local variable from ifblock should not be accessible now since we are in the parent block*/
		System.out.println("2nd line");
	}
}

Regards
Sourabh

[surli]

Hi @sourabhsparkala

I am trying to ffind all the possible list of CtLocalVariable or CtField which are accessible depending on the position at a point in code

Actually I think we had the contrary tool in Spoon: given a CtLocalVariable or a CtField we can give you the list of CtElements in which the variable or the field are visible. You may have a look on LocalVariableScopeFunction and FieldScopeFunction. Those functions are designed to be used inside a query, like in this snippet:

ctVar.map(new LocalVariableScopeFunction()).list()

Maybe @pvojtechovsky can give you some insights on those functions.

[pvojtechovsky]

Hi Sourabh,

yes, you can query for somethig like that. Have a look at documentation of LocalVariableReferenceFunction, LocalVariableScopeFunction and PotentialVariableDeclarationFunction. There is also a generic query function VariableReferenceFunction, which returns references to all kinds of variables. All of them can be used using example mentioned by Simon in the comment above.

I had similar need like you when I did algorithm for renaming of local variable. You can have a look at code of CtRenameLocalVariableRefactoring. It is not easy reading - rules for visibility of local variables in Java are tricky, but Spoon knows them all! So may be this is exactly what you need - You did not described why do you need such function.

Regards,
Pavel

[sourabhsparkala]

@pvojtechovsky @surli

Thank you for the reply. I want to find the influence of these variables in a code when statically analyzing the code. Hence I need this feature.

package app;


public class App 
{
	
	static int test = 0;
	public static void main(String[] args)
	{
		int local = 0;  /* The iftest local variable from ifblock should not be accessible within this outer parentblock. similarly the variables "local" and "test" should be accessible within this block.*/
		System.out.println("Hello world");
		
		if(test<3){   /* The iftest local variable should be accessible within this ifblock, not outside. similarly the variables "local" and "test" should be accessible within this block as well.*/
			
			int iftest = 10;
			test += 1;
		}
		 /* The iftest local variable from ifblock should not be accessible now since we are in the parent block*/
		System.out.println("2nd line");
	}
}

I went through the instruction functions, you suggested. But I am not sure where to start this from. As you can see in the above example. The challenge is ignoring the inner if-block variables from outer method-block.

i,e If I am at line System.out.println("2nd line"); in the code, from that position, The variable iftest declared within the if-block should be restricted only to that block. No-where else. Now from my current position in code. How do I find all variables within scope?

It would help me a lot if you can advise me on how to go about this.

Regards
Sourabh

[pvojtechovsky]

Start on the line System.out.println("2nd line"); and use PotentialVariableDeclarationFunction, which will return all the CtElements, which might be declaration of the variable visible on that line.

[sourabhsparkala]

This feature is too good.

Thanks a lot.

Regards
Sourabh

[sourabhsparkala]

Hello All,

The earlier implementation helped me a lot. However in the below example, the non-static variable "test" should not be accessible in the static method main. Yet on calling the PotentialVariableDeclarationFunction(), the non-static variable "test" is visible in the static main method.

package app;

public class App
{

int test = 0;
public static void main(String[] args)
{
	int local = 0; 
	System.out.println("Hello world");
	
	if(test<3){   
		
		int iftest = 10;
		test += 1;
	}
	System.out.println("2nd line");
}

}

Please let me know if you need more information

[pvojtechovsky]

Hi Sourabh,

It looks like you found a bug. I think the problem is understandable. Would be nice if you can fix PotentialVariableDeclarationFunction and add it as new pull request. Otherwise I will have a look at it when I have some time ...