[kevinherron]

Part 1 of 6 (#2118 to #2123) of a stack of server performance changes, found by profiling the Milo server in the o6-automation/opcua-benchmarks suite. This one is a correctness fix that the rest of the stack does not depend on; it is at the bottom because it is the smallest and safest.

Problem

Variant holds primitive arrays such as int[] and double[], for example from Variant.ofInt32Array(int[]), and the binary encoder writes them. A write of one through AttributeWriter still failed with Bad_TypeMismatch.

AttributeWriter.validateDataType took the array's component class, int.class for an int[], and asked DataTypeTree.isAssignable whether it fits the Variable's DataType. The tree only knows boxed backing classes such as Integer, so the answer was always no.

Two writes hit this:

• Server code that writes a primitive array through AttributeWriter, for example Variant.ofDoubleArray(new double[] {1, 2}) into a Double array Variable.
• A client Write with an IndexRange into a Variable whose stored value is a primitive array. The decoded update is a boxed Double[], but NumericRange.writeToValueAtRange merges it into a copy of the stored array, which keeps the primitive double[] form, and the merged value failed the check.

Whole-value client Writes were not affected, because the binary decoder always produces boxed arrays.

Change

validateDataType now uses ArrayUtil.getBoxedType, so a primitive array is accepted wherever its boxed form is. Boxed arrays, scalars, and Matrix values with boxed elements are checked exactly as before.

Tests

New cases in AttributeWriterTest (integration-tests):

• writePrimitiveArrayToVariableOfMatchingDataType: a double[] written to a Double array Variable is accepted and stored as double[].
• writePrimitiveMatrixToVariableOfMatchingDataType: a Matrix of int[][] written to an Int32 rank-2 Variable is accepted and stored.
• indexRangeWriteIntoStoredPrimitiveArrayUpdatesTheElement: a client Write of Double[] {9} at IndexRange "1" into a stored double[] {1, 2, 3} succeeds and stores double[] {1, 9, 3}.
• rejectPrimitiveArrayOfAnotherDataType (control): an int[] written to a Double Variable is still rejected.

On the unfixed base, the three positive tests fail with Bad_TypeMismatch.

Not changed

An IndexRange write whose update has the wrong element type, such as double[] into an int[], is reported as Bad_IndexRangeNoData instead of Bad_TypeMismatch, because NumericRange.writeToValueAtRange wraps every failure in Bad_IndexRangeNoData. That behavior predates this PR and is unchanged here.

Verification

• mvn -q -pl opc-ua-sdk/integration-tests -am test -Dtest=AttributeWriterTest: 45 tests pass.
• The full build with tests on the top of the stack (mvn -q -pl opc-ua-sdk/integration-tests -am verify): 451 test classes, 5,792 tests, no failures, 4 skipped.
• Reviewed independently by GPT-6.1-Sol (Codex) in two rounds; its findings (commit message scope, the IndexRange case, the Matrix assertion) are addressed above.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no actionable issues were found.

Summary

AttributeWriter now checks primitive arrays against their boxed element types, allowing matching arrays and matrices without changing their stored form.

• Primitive arrays pass value checks when their element types match.

No actionable issues were found. Tests were inspected but not run.

_{Reviews (1) · Last reviewed commit: "Accept primitive arrays in AttributeWrit..." · Reviewed by Greptile}