fix: prevent creating writable views when an input array is read-only

Author: kgryte

lib/node_modules/@stdlib/ndarray/iter/columns/README.md

@@ -76,7 +76,7 @@ arr = ndarray2array( v );
 
 The function accepts the following `options`:
 
--   **readonly**: boolean indicating whether returned [`ndarray`][@stdlib/ndarray/ctor] views should be read-only. Default: `true`.
+-   **readonly**: boolean indicating whether returned [`ndarray`][@stdlib/ndarray/ctor] views should be read-only. In order to return writable [`ndarray`][@stdlib/ndarray/ctor] views, the input [`ndarray`][@stdlib/ndarray/ctor] must be writable. If the input [`ndarray`][@stdlib/ndarray/ctor] is read-only, setting this option to `false` raises an exception. Default: `true`.
 
 By default, the iterator returns [`ndarray`][@stdlib/ndarray/ctor] views which are **read-only**. To return writable [views][@stdlib/ndarray/slice], set the `readonly` option to `false`.
 

lib/node_modules/@stdlib/ndarray/iter/columns/docs/repl.txt

@@ -20,7 +20,8 @@
 
     options.readonly: boolean (optional)
         Boolean indicating whether returned ndarray views should be read-only.
-        Default: true.
+        If the input ndarray is read-only, setting this option to `false` raises
+        an exception. Default: true.
 
     Returns
     -------

lib/node_modules/@stdlib/ndarray/iter/columns/docs/types/index.d.ts

@@ -32,6 +32,10 @@ type Iterator<T> = TypedIterator<T> | TypedIterableIterator<T>;
 interface Options {
 	/**
 	* Boolean indicating whether returned views should be read-only (default: true).
+	*
+	* ## Notes
+	*
+	* -   If the input array is read-only, setting this option to `false` raises an exception.
 	*/
 	readonly?: boolean;
 }

lib/node_modules/@stdlib/ndarray/iter/columns/lib/main.js

@@ -24,6 +24,7 @@ var setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-propert
 var isPlainObject = require( '@stdlib/assert/is-plain-object' );
 var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
 var isndarrayLike = require( '@stdlib/assert/is-ndarray-like' );
+var isReadOnly = require( '@stdlib/ndarray/base/assert/is-read-only' );
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var iteratorSymbol = require( '@stdlib/symbol/iterator' );
 var zeros = require( '@stdlib/array/base/zeros' );
@@ -46,6 +47,7 @@ var format = require( '@stdlib/string/format' );
 * @throws {TypeError} first argument must have at least two dimensions
 * @throws {TypeError} options argument must be an object
 * @throws {TypeError} must provide valid options
+* @throws {Error} cannot write to a read-only array
 * @returns {Iterator} iterator
 *
 * @example
@@ -106,6 +108,9 @@ function nditerColumns( x ) {
 				throw new TypeError( format( 'invalid option. `%s` option must be a boolean. Option: `%s`.', 'readonly', options.readonly ) );
 			}
 			opts.writable = !options.readonly;
+			if ( opts.writable && isReadOnly( x ) ) {
+				throw new Error( format( 'invalid option. Cannot write to read-only array.' ) );
+			}
 		}
 	}
 	// Retrieve input array meta data:

lib/node_modules/@stdlib/ndarray/iter/columns/test/test.js

@@ -155,6 +155,20 @@ tape( 'the function throws an error if provided a `readonly` option which is not
 	}
 });
 
+tape( 'the function throws an error if provided a `readonly` option which equal to `false` when the input array is read-only', function test( t ) {
+	t.throws( badValue, Error, 'throws an error' );
+	t.end();
+
+	function badValue() {
+		var x = zeros( [ 2, 2 ], {
+			'readonly': true
+		});
+		nditerColumns( x, {
+			'readonly': false
+		});
+	}
+});
+
 tape( 'the function throws an error if provided an ndarray having fewer than two dimensions', function test( t ) {
 	var values;
 	var i;