Set WP_TEMP_DIR for Contact Form 7 uploads (#4901)

The plugin ignores the value of `WPCF7_UPLOADS_TMP_DIR` if it is not
within a set of paths allowed by the plugin. The plugin allows the path
defined in `WP_TEMP_DIR`, so this fix uses the plugin's `wpcf7_upload_dir`
filter to set `WP_TEMP_DIR` to `/tmp/` so that the plugin will allow the
path that we defined earlier in `WPCF7_UPLOADS_TMP_DIR`.

plugin-fixes.php

@@ -18,6 +18,27 @@
 	define( 'WPCF7_UPLOADS_TMP_DIR', get_temp_dir() . 'cf7/' );
 }
 
+/**
+ * Contact Form 7 (https://wordpress.org/plugins/contact-form-7/)
+ *
+ * The plugin ignores the value of `WPCF7_UPLOADS_TMP_DIR` if it is not
+ * within a set of paths allowed by the plugin. The plugin allows the path
+ * defined in `WP_TEMP_DIR`, so this fix uses the plugin's `wpcf7_upload_dir`
+ * filter to set `WP_TEMP_DIR` to `/tmp/` so that the plugin will allow the
+ * path that we defined earlier in `WPCF7_UPLOADS_TMP_DIR`.
+ *
+ * @param array $uploads See wp_upload_dir() for description.
+ * @return array Information about the upload directory.
+ */
+function vip_wpcf7_upload_dir( $uploads ) {
+	if ( ! defined( 'WP_TEMP_DIR' ) ) {
+		define( 'WP_TEMP_DIR', get_temp_dir() );
+	}
+
+	return $uploads;
+}
+add_filter( 'wpcf7_upload_dir', 'vip_wpcf7_upload_dir', 10, 1 );
+
 /**
  * Recent versions of CF7 attempt to clean-up uploaded attachments
  * somewhere within `wp-content`, ignoring the value of WPCF7_UPLOADS_TMP_DIR if