Properly remove no longer needed editors

Some failed requests used to leave defunct editors listening to messages. In the worst case those zombie editors would receive diagram data not intended for them and overwrite the contents of wrong files.

Author: annda

script/helpers.js

@@ -1,6 +1,30 @@
 const serviceUrl = 'https://embed.diagrams.net/?embed=1&proto=json&spin=1';
 const doctypeXML = '<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">';
 
+/**
+ * Return the diagrams editor object or false
+ * if it does not exist.
+ *
+ * @returns {boolean|WindowProxy}
+ */
+function getDiagramsEditor() {
+    const diagramsFrame = jQuery('#diagrams-frame');
+    if (diagramsFrame  && typeof diagramsFrame[0] !== 'undefined') {
+        return diagramsFrame[0].contentWindow;
+    }
+    return false;
+}
+
+/**
+ * Detach the message event handler and remove the editor
+ *
+ * @param handler
+ */
+function removeDiagramsEditor(handler) {
+    jQuery(window).off( 'message', handler );
+    jQuery('#diagrams-frame').remove();
+}
+
 /**
  * check if name/id of new diagram is valid
  *

script/service.js

@@ -4,12 +4,17 @@
  * @param event
  */
 const handleServiceMessages = function( event ) {
+    const diagrams = getDiagramsEditor();
+    // early exit
+    if (!diagrams) {
+        return;
+    }
+
     // get diagram info passed to the function
     const fullId = event.data.fullId;
     const {ns, id} = splitFullId(fullId);
 
     const msg = JSON.parse( event.originalEvent.data );
-    const diagrams = jQuery( '#diagrams-frame' )[0].contentWindow;
     if( msg.event === 'init' ) {
         // try loading existing diagram file
         jQuery.get(DOKU_BASE + 'lib/exe/fetch.php?media=' + fullId, function (data) {
@@ -33,8 +38,6 @@ const handleServiceMessages = function( event ) {
                 } ).join( '' ) );
             jQuery.post( getLocalDiagramUrl(ns, id), datastr )
                 .done( function() {
-                    jQuery( window ).off( 'message', {fullId: fullId}, handleServiceMessages );
-                    jQuery( '#diagrams-frame' ).remove();
                     const url = new URL(location.href);
                     // media manager window should show current namespace
                     url.searchParams.set('ns', ns);
@@ -44,10 +47,12 @@ const handleServiceMessages = function( event ) {
                 })
                 .fail( function() {
                     alert( LANG.plugins.diagrams.errorSaving );
+                })
+                .always( function() {
+                    removeDiagramsEditor(handleServiceMessages);
                 });
         }
     } else if( msg.event === 'exit' ) {
-        jQuery( window ).off( 'message', {fullId: fullId}, handleServiceMessages );
-        jQuery( '#diagrams-frame' ).remove();
+        removeDiagramsEditor(handleServiceMessages);
     }
 };