fix: avoid mutating source array

lib/node_modules/@stdlib/array/fixed-endian-factory/lib/main.js

@@ -37,6 +37,7 @@
 var isPrototypeOf = require( '@stdlib/assert/is-prototype-of' ); // eslint-disable-line stdlib/no-redeclare
 var setReadOnlyAccessor = require( '@stdlib/utils/define-nonenumerable-read-only-accessor' );
 var ArrayBuffer = require( '@stdlib/array/buffer' );
+var Uint8Array = require( '@stdlib/array/uint8' );
 var DataView = require( '@stdlib/array/dataview' );
 var getter = require( '@stdlib/array/base/getter' );
 var accessorGetter = require( '@stdlib/array/base/accessor-getter' );
@@ -225,7 +226,7 @@
 	* Typed array constructor which returns a typed array representing an array of values in a specified byte order.
 	*
 	* @private
 	* @constructor
 	* @param {string} endianness - byte order
 	* @param {(NonNegativeInteger|Collection|ArrayBuffer|Iterable)} [arg] - length, typed array, array-like object, buffer, or an iterable
 	* @param {NonNegativeInteger} [byteOffset=0] - byte offset
@@ -1141,6 +1142,9 @@
 	*/
 	setReadOnly( TypedArray.prototype, 'with', function copyWith( index, value ) {
 		var outbuf;
+		var nbytes;
+		var dest;
+		var src;
 		var buf;
 		var out;
 		var len;
@@ -1159,7 +1163,11 @@
 		if ( index < 0 || index >= len ) {
 			throw new RangeError( format( 'invalid argument. Index argument is out-of-bounds. Value: `%s`.', index ) );
 		}
-		out = new this.constructor( flag2byteOrder( this._isLE ), buf.buffer );
+		nbytes = len * BYTES_PER_ELEMENT;
+		src = new Uint8Array( buf.buffer, buf.byteOffset, nbytes );
+		dest = new Uint8Array( new ArrayBuffer( nbytes ) );
+		dest.set( src );
+		out = new this.constructor( flag2byteOrder( this._isLE ), dest.buffer );
 		outbuf = out._buffer;  // eslint-disable-line no-underscore-dangle
 		outbuf[ SETTER ]( index * BYTES_PER_ELEMENT, value, this._isLE );
 		return out;

lib/node_modules/@stdlib/array/fixed-endian-factory/test/test.with.js

@@ -24,6 +24,7 @@ var tape = require( 'tape' );
 var hasSameValues = require( '@stdlib/array/base/assert/has-same-values' );
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var isFunction = require( '@stdlib/assert/is-function' );
+var ArrayBuffer = require( '@stdlib/array/buffer' );
 var factory = require( './../lib' );
 
 
@@ -187,3 +188,57 @@ tape( 'the method supports negative indices', function test( t ) {
 	t.notEqual( actual, arr, 'returns new instance' );
 	t.end();
 });
+
+tape( 'the method does not mutate the original array', function test( t ) {
+	var expected;
+	var actual;
+	var ctor;
+	var arr;
+
+	ctor = factory( 'float64' );
+	arr = new ctor( 'little-endian', [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
+	expected = new ctor( 'little-endian', [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
+	actual = arr.with( 0, 0.0 );
+
+	t.notEqual( actual.buffer, arr.buffer, 'returns expected value' );
+	t.strictEqual( hasSameValues( arr, expected ), true, 'returns expected value' );
+	t.end();
+});
+
+tape( 'the method supports typed arrays which are views on an underlying buffer', function test( t ) {
+	var expected;
+	var actual;
+	var ctor;
+	var arr;
+	var buf;
+
+	ctor = factory( 'float64' );
+	buf = new ArrayBuffer( 40 );
+	arr = new ctor( 'little-endian', buf, 8, 3 );
+	arr.set( [ 1.0, 2.0, 3.0 ] );
+
+	expected = new ctor( 'little-endian', [ 1.0, 0.0, 3.0 ] );
+	actual = arr.with( 1, 0.0 );
+
+	t.strictEqual( actual.length, 3, 'returns expected value' );
+	t.strictEqual( hasSameValues( actual, expected ), true, 'returns expected value' );
+
+	expected = new ctor( 'little-endian', [ 1.0, 2.0, 3.0 ] );
+	t.strictEqual( hasSameValues( arr, expected ), true, 'returns expected value' );
+	t.end();
+});
+
+tape( 'the method returns a typed array having the same byte order as the original array', function test( t ) {
+	var expected;
+	var actual;
+	var ctor;
+	var arr;
+
+	ctor = factory( 'float64' );
+	arr = new ctor( 'big-endian', [ 1.0, 2.0, 3.0 ] );
+	expected = new ctor( 'big-endian', [ 1.0, 2.0, 0.0 ] );
+	actual = arr.with( 2, 0.0 );
+
+	t.strictEqual( hasSameValues( actual, expected ), true, 'returns expected value' );
+	t.end();
+});