Ticket #35069: 35069.4.diff

src/wp-includes/pluggable.php

@@ -183 +183 @@
          */
         $atts = apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) );
 
+        /**
+         * Filter whether to preempt sending an email.
+         *
+         * Passing a truthy value will effectively short-circuit {@see wp_mail()},
+         * returning that value instead.
+         *
+         * @since 4.5.0
+         *
+         * @param bool  $return Short-circuit return value.
+         * @param array $args   A compacted array of wp_mail() arguments, including the "to" email,
+         *                      subject, message, headers, and attachments values.
+         */
+        $pre_wp_mail = apply_filters( 'pre_wp_mail', null, $atts );
+
+        if ( ! is_null ( $pre_wp_mail ) ) {
+                return $pre_wp_mail;
+        }
+
         if ( isset( $atts['to'] ) ) {
                 $to = $atts['to'];
         }

tests/phpunit/tests/mail.php

@@ -392 +392 @@
                 $this->assertEquals( 'wp_mail_failed', $call_args[0]->get_error_code() );
                 $this->assertEquals( $expected_error_data, $call_args[0]->get_error_data() );
         }
+
+        /**
+         * @ticket 35069
+         */
+        public function test_wp_mail_bail_early() {
+                $this->assertTrue( wp_mail( WP_TESTS_EMAIL, 'Foo', 'Bar' ) );
+
+                add_filter( 'pre_wp_mail', '__return_null' );
+                $this->assertNull( wp_mail( WP_TESTS_EMAIL, 'Foo', 'Bar' ) );
+                remove_filter( 'pre_wp_mail', '__return_null' );
+        }
 }