Vite resolve.alias causes some tests to fail

[rudolfbyker]

Subject of the issue

It looks like vitest is not respecting the resolve.alias setting from the vite config file.

Steps to reproduce

See https://github.com/rudolfbyker/vitest-vue2-vuetify-repro

Expected behaviour

The test should pass.

Actual behaviour

"Cannot read properties of undefined" whenever we try to access something like "$vuetify" on a Vue instance.

Possible Solution

No solutions, but some workarounds:

Workaround 1: Monkey-one of my colleagues found a workaround. However, it's a bit arduous when there are many tests:patch the require function in tests (yuck)

1. Use alias vue: "vue/dist/vue.common.js" instead of vue: "vue/dist/vue.esm.js".
2. Create a utility function

export function forceVueAlias(overwrite: string) {
  // Load global module.
  const globalModule = require('module');
  // Save original require method.
  const _require = globalModule.prototype.require;

  globalModule.prototype.require = function () {
    if (arguments["0"] === "vue") arguments["0"] = overwrite;

    // Return result from original function.g
    return _require.apply(this, arguments);
  };
}

3. Use it at the top of every test:

forceVueAlias("vue/dist/vue.common.js");

Workaround 2:

Don't use aliases. But then I can't have the runtime compiler for my project, which is a big problem.

Workaround 3:

import { defineConfig, loadEnv } from "vite";

export default defineConfig(({ command, mode }) => {
  const env = loadEnv(mode, process.cwd(), "");

  return {
    resolve: {
      alias: {
        // This enables the runtime compiler for Vue 2.
        vue: "vue/dist/vue.esm.js",
      },
    },
    
    test: {
      alias: {
        // Disable the runtime compiler during tests.
        vue: "vue",
      },
    },
  };
});

[rudolfbyker]

The above-mentioned "workaround 1" causes a few other problems, where some getCurrentInstance is returning null inside some composables, like useRoute. Not sure why, yet. It would be great if there was a way to either

• let vitest respect the resolve.alias
• enable runtime compiler in the actual app AND in tests without using aliases