Prevent self-composition in layouts (#2287)

src/api/objects/ObjectAPI.js

@@ -215,6 +215,19 @@ define([
         return utils.makeKeyString(identifier);
     };
 
+    /**
+     * Given any number of identifiers, will return true if they are all equal, otherwise false.
+     * @param {module:openmct.ObjectAPI~Identifier[]} identifiers
+     */
+    ObjectAPI.prototype.areIdsEqual = function (...identifiers) {
+        return identifiers.map(utils.parseKeyString)
+            .every(identifier => {
+                return identifier === identifiers[0] ||
+                    (identifier.namespace === identifiers[0].namespace &&
+                        identifier.key === identifiers[0].key);
+            });
+    }
+
     /**
      * Uniquely identifies a domain object.
      *