Transport\Curl/Fsockopen::request_multiple(): add input validation

This commit adds input validation to the `Curl::request_multiple()` and the `Fsockopen::request_multiple()` methods along the same lines as added to `Requests::request_multiple()`.

* For `$requests`, arrays and iterable objects with array access should be accepted based on how the parameter is used within this class.
* The `$options` parameter is validated to allow only an array - same as in `Requests::request()`.

Includes aligning the behaviour when receiving an empty `$requests` array between the `Curl` and the `Fsockopen` classes and returning an empty array in that case.

Includes adding perfunctory tests for the new exceptions.

src/Transport/Curl.php

@@ -231,13 +231,24 @@ public function request($url, $headers = [], $data = [], $options = []) {
 	 * @param array $requests Request data
 	 * @param array $options Global options
 	 * @return array Array of \WpOrg\Requests\Response objects (may contain \WpOrg\Requests\Exception or string responses as well)
+	 *
+	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $requests argument is not an array or iterable object with array access.
+	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $options argument is not an array.
 	 */
 	public function request_multiple($requests, $options) {
 		// If you're not requesting, we can't get any responses ¯\_(ツ)_/¯
 		if (empty($requests)) {
 			return [];
 		}
 
+		if (InputValidator::has_array_access($requests) === false || InputValidator::is_iterable($requests) === false) {
+			throw InvalidArgument::create(1, '$requests', 'array|ArrayAccess&Traversable', gettype($requests));
+		}
+
+		if (is_array($options) === false) {
+			throw InvalidArgument::create(2, '$options', 'array', gettype($options));
+		}
+
 		$multihandle = curl_multi_init();
 		$subrequests = [];
 		$subhandles  = [];

src/Transport/Fsockopen.php

@@ -344,8 +344,24 @@ public function request($url, $headers = [], $data = [], $options = []) {
 	 * @param array $requests Request data (array of 'url', 'headers', 'data', 'options') as per {@see \WpOrg\Requests\Transport::request()}
 	 * @param array $options Global options, see {@see \WpOrg\Requests\Requests::response()} for documentation
 	 * @return array Array of \WpOrg\Requests\Response objects (may contain \WpOrg\Requests\Exception or string responses as well)
+	 *
+	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $requests argument is not an array or iterable object with array access.
+	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $options argument is not an array.
 	 */
 	public function request_multiple($requests, $options) {
+		// If you're not requesting, we can't get any responses ¯\_(ツ)_/¯
+		if (empty($requests)) {
+			return [];
+		}
+
+		if (InputValidator::has_array_access($requests) === false || InputValidator::is_iterable($requests) === false) {
+			throw InvalidArgument::create(1, '$requests', 'array|ArrayAccess&Traversable', gettype($requests));
+		}
+
+		if (is_array($options) === false) {
+			throw InvalidArgument::create(2, '$options', 'array', gettype($options));
+		}
+
 		$responses = [];
 		$class     = get_class($this);
 		foreach ($requests as $id => $request) {

tests/Transport/BaseTestCase.php

@@ -2,6 +2,7 @@
 
 namespace WpOrg\Requests\Tests\Transport;
 
+use EmptyIterator;
 use stdClass;
 use WpOrg\Requests\Capability;
 use WpOrg\Requests\Exception;
@@ -333,6 +334,88 @@ public function testRequestInvalidOptions($input) {
 		$transport->request('/', [], [], $input);
 	}
 
+	/**
+	 * Tests receiving an exception when the request_multiple() method received an invalid input type as `$requests`.
+	 *
+	 * @dataProvider dataRequestMultipleReturnsEmptyArrayWhenRequestsIsEmpty
+	 *
+	 * @covers \WpOrg\Requests\Transport\Curl::request_multiple
+	 * @covers \WpOrg\Requests\Transport\Fsockopen::request_multiple
+	 *
+	 * @param mixed $input Invalid parameter input.
+	 *
+	 * @return void
+	 */
+	public function testRequestMultipleReturnsEmptyArrayWhenRequestsIsEmpty($input) {
+		$transport = new $this->transport();
+		$this->assertSame([], $transport->request_multiple($input, $this->getOptions()));
+	}
+
+	/**
+	 * Data Provider.
+	 *
+	 * @return array
+	 */
+	public function dataRequestMultipleReturnsEmptyArrayWhenRequestsIsEmpty() {
+		return [
+			'null'        => [null],
+			'empty array' => [[]],
+		];
+	}
+
+	/**
+	 * Tests receiving an exception when the request_multiple() method received an invalid input type as `$requests`.
+	 *
+	 * @dataProvider dataRequestMultipleInvalidRequests
+	 *
+	 * @covers \WpOrg\Requests\Transport\Curl::request_multiple
+	 * @covers \WpOrg\Requests\Transport\Fsockopen::request_multiple
+	 *
+	 * @param mixed $input Invalid parameter input.
+	 *
+	 * @return void
+	 */
+	public function testRequestMultipleInvalidRequests($input) {
+		$this->expectException(InvalidArgument::class);
+		$this->expectExceptionMessage('Argument #1 ($requests) must be of type array|ArrayAccess&Traversable');
+
+		$transport = new $this->transport();
+		$transport->request_multiple($input, $this->getOptions());
+	}
+
+	/**
+	 * Data Provider.
+	 *
+	 * @return array
+	 */
+	public function dataRequestMultipleInvalidRequests() {
+		return [
+			'text string'                          => ['array'],
+			'iterator object without array access' => [new EmptyIterator()],
+			'array accessible object not iterable' => [new ArrayAccessibleObject([1, 2, 3])],
+		];
+	}
+
+	/**
+	 * Tests receiving an exception when the request_multiple() method received an invalid input type as `$option`.
+	 *
+	 * @dataProvider dataInvalidTypeNotArray
+	 *
+	 * @covers \WpOrg\Requests\Transport\Curl::request_multiple
+	 * @covers \WpOrg\Requests\Transport\Fsockopen::request_multiple
+	 *
+	 * @param mixed $input Invalid parameter input.
+	 *
+	 * @return void
+	 */
+	public function testRequestMultipleInvalidOptions($input) {
+		$this->expectException(InvalidArgument::class);
+		$this->expectExceptionMessage('Argument #2 ($options) must be of type array');
+
+		$transport = new $this->transport();
+		$transport->request_multiple(['notempty'], $input);
+	}
+
 	/**
 	 * Data Provider.
 	 *