Using XPath for PMD, is there a way to account for the value of a variable in a method call?

Issue

For example:

String user = "Daniel";
String result = doSomething(user);

I know I can find every occurence of doSomething(user) with //MethodCall[@MethodName = "doSomething"]/ArgumentList/VariableAccess[@Name = "user"]. Is it possible to only find those occurences, where user evaluates to "Daniel" at the time the method is called?

Solution

Both MethodCall and VariableDeclarator are descendants of the same Block element. That can be used to match the criteria

//Block[//AssignmentExpression[last()][VariableAccess[@AccessType="WRITE" and @Name="user"]]/StringLiteral[@ConstValue="LMC"] or //VariableDeclarator[@Name="user"]/StringLiteral[@ConstValue="LMC"]]//MethodCall[@MethodName = "detectMe"]/ArgumentList/VariableAccess[@Name = "user"]

This expresion finds Block elements containing a variable user = "LMC" either only declared or last assigned.

//Block[//AssignmentExpression[last()][VariableAccess[@AccessType="WRITE" and @Name="user"]]/StringLiteral[@ConstValue="LMC"] or //VariableDeclarator[@Name="user"]/StringLiteral[@ConstValue="LMC"]]

Will match something like

public void useIt(){
    String user = "LMC";
    String result = detectMe(user);
}
public void useIt(2){
    String user = "Daniel";
    
    user = "osoo";
    user = "LMC";
    String result = detectMe(user);
}

As a general method, a test class with the relevant use case can be written and dumped with pmd for later XML analysis

pmd ast-dump --format xml --language java --file PMDSource.java > PMDSource.java.xml

then use any XPath aware tool to test the expression

 xmllint --xpath '//Block[//AssignmentExpression[last()][VariableAccess[@AccessType="WRITE" and @Name="user"]]/StringLiteral[@ConstValue="LMC"] or //VariableDeclarator[@Name="user"]/StringLiteral[@ConstValue="LMC"]]//MethodCall[@MethodName = "detectMe"]/ArgumentList/VariableAccess[@Name = "user"]' PMDSource.java.xml 

Result

<VariableAccess AccessType="READ" CompileTimeConstant="false" Expression="true" Image="user" Name="user" ParenthesisDepth="0" Parenthesized="false"/>
<VariableAccess AccessType="READ" CompileTimeConstant="false" Expression="true" Image="user" Name="user" ParenthesisDepth="0" Parenthesized="false"/>

Answered By - LMC