Implement in $:/core/upgraders instead of navigator.js

The core module tiddlers are not blocked, they are only marked.

core/language/en-GB/Import.multids

@@ -18,5 +18,6 @@ Upgrader/Plugins/Suppressed/Version: Blocked plugin (due to incoming <<incoming>
 Upgrader/Plugins/Upgraded: Upgraded plugin from <<incoming>> to <<upgraded>>
 Upgrader/State/Suppressed: Blocked temporary state tiddler
 Upgrader/System/Suppressed: Blocked system tiddler
+Upgrader/System/Warning: Warning: Core module tiddler
+Upgrader/System/Alert: You are about importing core module tiddlers. It is strongly recommend in the strongest terms NOT to use any hack that requires overwriting a core module, because it is likely to make the system unusable. Never import such tiddlers into an important wiki, just into a testing environment!
 Upgrader/ThemeTweaks/Created: Migrated theme tweak from <$text text=<<from>>/>
-Warning/Core: You are about importing risky tiddlers (<<titles>>). It is strongly recommend in the strongest terms NOT to use any hack that requires overwriting a core module, because it is likely to make the system unusable. Never import such tiddlers into an important wiki, just into a testing environment!

core/modules/upgraders/system.js

@@ -13,11 +13,13 @@ Upgrader module that suppresses certain system tiddlers that shouldn't be import
 "use strict";
 
 var DONT_IMPORT_LIST = ["$:/StoryList","$:/HistoryList"],
-	DONT_IMPORT_PREFIX_LIST = ["$:/temp/","$:/state/"];
+	DONT_IMPORT_PREFIX_LIST = ["$:/temp/","$:/state/"],
+	WARN_IMPORT_PREFIX_LIST = ["$:/core/modules/"];
 
 exports.upgrade = function(wiki,titles,tiddlers) {
 	var self = this,
-		messages = {};
+		messages = {},
+		showAlert = false;
 	// Check for tiddlers on our list
 	$tw.utils.each(titles,function(title) {
 		if(DONT_IMPORT_LIST.indexOf(title) !== -1) {
@@ -31,6 +33,17 @@ exports.upgrade = function(wiki,titles,tiddlers) {
 					messages[title] = $tw.language.getString("Import/Upgrader/State/Suppressed");
 				}
 			}
+			for(var t=0; t<WARN_IMPORT_PREFIX_LIST.length; t++) {
+				var prefix = WARN_IMPORT_PREFIX_LIST[t];
+				if(title.substr(0,prefix.length) === prefix) {
+					showAlert = true;
+					messages[title] = $tw.language.getString("Import/Upgrader/System/Warning");
+				}
+			}
+		}
+		if(showAlert) {
+			var logger = new $tw.utils.Logger("import");
+			logger.alert($tw.language.getString("Import/Upgrader/System/Alert"));
 		}
 	});
 	return messages;

core/modules/widgets/navigator.js

@@ -485,8 +485,7 @@ NavigatorWidget.prototype.handleNewTiddlerEvent = function(event) {
 // Import JSON tiddlers into a pending import tiddler
 NavigatorWidget.prototype.handleImportTiddlersEvent = function(event) {
 	// Get the tiddlers
-	var tiddlers = [],
-		warning = [];
+	var tiddlers = [];
 	try {
 		tiddlers = JSON.parse(event.param);
 	} catch(e) {
@@ -507,26 +506,10 @@ NavigatorWidget.prototype.handleImportTiddlersEvent = function(event) {
 		tiddlerFields.title = $tw.utils.trim(tiddlerFields.title);
 		var title = tiddlerFields.title;
 		if(title) {
-			if(title.indexOf('$:/core/') === 0) {
-				warning.push(title);
-			}
 			incomingTiddlers.push(title);
 			importData.tiddlers[title] = tiddlerFields;
 		}
 	});
-	// Show warning about risky tiddlers
-	if(warning.length) {
-		var titles = [];
-		$tw.utils.each(warning,function(title) {
-			titles.push(title);
-		});
-		var logger = new $tw.utils.Logger("import");
-		logger.alert($tw.language.getString(
-			"Import/Warning/Core",
-			{variables: {
-			"titles": titles.join(", "),
-		}}));
-	}
 	// Give the active upgrader modules a chance to process the incoming tiddlers
 	var messages = this.wiki.invokeUpgraders(incomingTiddlers,importData.tiddlers);
 	$tw.utils.each(messages,function(message,title) {