There are two issues.

1. The spec for method javax.script.SimpleScriptContext.getAttributesScope(String name) says that method should return -1 if no attribute with the given name is defined in any scope.
In fact, the method returns 0 in this case. Here is an example:

...
final SimpleScriptContext ctx = new SimpleScriptContext();
final String name = getClass().getName() + "#newkey";
System.out.println("Expected: result=-1");
System.out.println("Returned: result=" + ctx.getAttributesScope(name));
...

2. Method getAttributesScope can not find the scope for attribute with the null value. Here is an example:

...
final SimpleScriptContext ctx = new SimpleScriptContext();
final String name = getClass().getName() + "#newkey";
ctx.setAttribute(name, null, ScriptContext.ENGINE_SCOPE);
System.out.println("Expected: result=" + ScriptContext.ENGINE_SCOPE);
System.out.println("Returned: result=" + ctx.getAttributesScope(name));
...

It seems such behavior should be clarified in the spec.
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