The error message is not user-friendly when adding duplicate permissi…

plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/controller/PermissionController.java

@@ -105,4 +105,18 @@ public Object deletePermission(@RequestParam String role, @RequestParam String r
         nacosRoleService.deletePermission(role, resource, action);
         return RestResultUtils.success("delete permission ok!");
     }
+
+    /**
+     * Judge whether a permission is duplicate.
+     *
+     * @param role     the role
+     * @param resource the related resource
+     * @param action   the related action
+     * @return true if duplicate, false otherwise
+     */
+    @GetMapping
+    @Secured(resource = AuthConstants.CONSOLE_RESOURCE_NAME_PREFIX + "permissions", action = ActionTypes.READ)
+    public Boolean isDuplicatePermission(@RequestParam String role, @RequestParam String resource, @RequestParam String action) {
+        return nacosRoleService.isDuplicatePermission(role, resource, action);
+    }
 }

plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/roles/NacosRoleServiceImpl.java

@@ -370,5 +370,28 @@ public boolean hasGlobalAdminRole() {
         authConfigs.setHasGlobalAdminRole(hasGlobalAdminRole);
         return hasGlobalAdminRole;
     }
+
+    /**
+     * judge whether the permission is duplicate.
+     *
+     * @param role role name
+     * @param resource resource
+     * @param action action
+     * @return true if duplicate, false otherwise
+     */
+    public Boolean isDuplicatePermission(String role, String resource, String action) {
+        List<PermissionInfo> permissionInfos = getPermissions(role);
+        if (CollectionUtils.isEmpty(permissionInfos)) {
+            return Boolean.FALSE;
+        }
+        for (PermissionInfo permissionInfo : permissionInfos) {
+            boolean resourceMatch = StringUtils.equals(resource, permissionInfo.getResource());
+            boolean actionMatch = StringUtils.equals(action, permissionInfo.getAction()) || "rw".equals(permissionInfo.getAction());
+            if (resourceMatch && actionMatch) {
+                return Boolean.TRUE;
+            }
+        }
+        return Boolean.FALSE;
+    }
 
 }