“$attrs is readonly”,“$listeners is readonly”,“Avoid mutating a prop directly”

Question

I am new to Vue. I am trying to develop a chatting application where friend list will be shown on the left menu and the chat box will be shown at the body. I am loading frie

Answer 1

I faced the same problem. For me, as I installed a local module using

yarn add ../somemodule --force

Seems this command will copy the whole module directory include the node_modules sub-directory. That causes the duplication of the same version of "vue" module. And in the browser devtool I can see multiple sources of the module.

For me, the solution is manually to delete the node_modules every time after install the local module.

Answer 2

In my case, I was migrating from a project that didn't use VueCLI. In that project, I imported vue from a CDN <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>. In my Vue CLI project, I had copied and pasted my whole index.html file to the Public folder. Vue CLI has it's own way of importing vue so they were clashing. I simply removed the script and the problem was solved.

Answer 3

Adding this to vue.config.js, worked for me.

const path = require('path')

module.exports = {
  configureWebpack: {
    externals: {
      vue: 'Vue'
    }
  }
}

Answer 4

This error was happening to me because I was using Git submodules in my project and I had the following folders:

• ./node_modules - this is for the main project. There was vue installed in these node_modules.
• ./my_git_submodules/vue_design_system/node_modules - design system that provides basic components (also uses vue). Vue was also installed here!!

So because both:

• ./node_modules/vue and
• ./my_git_submodules/vue_design_system/node_modules/vue

existed, running npm run serve (vue-cli-service build underneath) built two instances of Vue. This was a really nasty issue because it broke reactivity in certain cases (ie. you click a button and nothing happens - you just get the $listeners readonly error)

Quick fix:
removing node_modules in the child folder (vue_design_system) and running npm run serve worked for me.

Long term fix:
you'll probably need to make Webpack ignore nested node_modules folders by adding a rule in vue.config.js

Answer 5

Adding this to main.js, worked for me.

Vue.config.silent = true;

Answer 6

First, these errors only come out in non-production builds, however they indicate a problem that should be resolved before production release.

The $attrs, $listeners and other warnings are displayed if there's more than one instance of Vue loaded. As I understand it, this can happen usually for one these reasons:

• it is being loaded/packed into the bundle by webpack and also loaded externally (not via webpack)
• it is being loaded by something you include (e.g. vuetify, vue-test-utils, vue-cli-electron-builder) one way and by your webpack config another way (e.g. absolute vs relative paths, common.js vs esm.js vue files, runtime-only vue vs compiler+runtime vue)

If you click on that line (it was app.js:19302 in your output above) and put a breakpoint where the message is coming out, you can see the list of modules in the stack traceback to see if there's more than one path to Vue listed. For example, see that the top three modules have a different path below (but are all part of Vue): If you see Vue showing up in two or more different ways, it demonstrates that more than one instance of Vue is loaded. Vue only supports a single instance, and can produce these error messages if more than one is loaded.

There are several links to issues included above, the Vuetify issue was the one I filed. In that case, Vuetify requires Vue and was loading it differently than I was. Usually the fix is to check your webpack config where Vue is specified (or isn't) and try to make it match the way the other copy is being included (e.g. absolute vs relative path, or packed vs external).