Ticket #35069: 35069.6.patch

src/wp-includes/pluggable.php

@@ -180 +180 @@
                  */
                 $atts = apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) );
 
+                /**
+                * Filter whether to preempt sending an email.
+                *
+                * Passing a non-null value will effectively short-circuit {@see wp_mail()},
+                * returning that value instead.
+                *
+                * @since 5.0.0
+                *
+                * @param null|bool $return Short-circuit return value.
+                * @param array     $atts   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 ( null !== $pre_wp_mail ) {
+                        return $pre_wp_mail;
+                }
+
                 if ( isset( $atts['to'] ) ) {
                         $to = $atts['to'];
                 }

tests/phpunit/tests/mail.php

@@ -407 +407 @@
                 $this->assertEquals( 'wp_mail_failed', $call_args[0]->get_error_code() );
                 $this->assertEquals( $expected_error_data, $call_args[0]->get_error_data() );
         }
+
+        /**
+         * Test for bailing out of wp_mail() early.
+         *
+         * @ticket 35069
+         */
+        public function test_wp_mail_bail_early() {
+                $this->assertTrue( wp_mail( WP_TESTS_EMAIL, 'Foo', 'Bar' ) );
+
+                add_filter( 'pre_wp_mail', '__return_false' );
+                $result = wp_mail( WP_TESTS_EMAIL, 'Foo', 'Bar' );
+                remove_filter( 'pre_wp_mail', '__return_false' );
+
+                $this->assertFalse( $result );
+        }
 }