JDK-8138632 : Sparse array does not handle growth of underlying dense array
  • Type: Bug
  • Component: core-libs
  • Sub-Component: jdk.nashorn
  • Affected Version: 8
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2015-09-30
  • Updated: 2016-01-14
  • Resolved: 2015-10-01
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JDK 8 JDK 9
8u72Fixed 9 b85Fixed
Description
When an element is set in a sparse array that is stored in the underlying dense array and causes the dense array to grow, the elements between the old dense array length and the new index are not deleted. 

var x = [];
x[10000000] = 1;
x[10] = 1;
x[20] = 1;
print(Object.keys(x));

Expected output: 
10,20,10000000

Actual output:
0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,10000000

The fix is to add functionality similar to that in ScriptObject.doesNotHaveEnsureDelete in SparseArrayData.set.