Can't mock package 'vue' if it doesn't installed

[cawa-93]

My case: I have generated package like below:

import {h} from 'vue';
export const ComponentName = () => h('svg', { /* some properties */ });

And I want to test this package. The point of the test is just to check that function h was called with the correct parameters.

So I tried mock h function from vue

// test.spec.js
const component= await esmock(`../component.js`, {}, {
  vue: {
    h: (...args) => args
  }
})

It works great. But, only if the vue is installed as a dependency. Because in reality no vue functionality is used anywhere, I tried to remove this dependency, but then I get the error:

not a valid path: "vue" 

What can I do about it? I wouldn't want to install an entire framework just to mock a single function in tests.

You can reproduce the problem

1. Clone repo: git clone https://github.com/cawa-93/iconify-prerendered.git
2. Delete vue dependency: npm un vue
3. Install others dependencies: npm ci
4. Generate code for testing: npm run build
5. Run test: npm run test

[iambumblehead]

this is an interesting scenario I did not think of @cawa-93

[iambumblehead]

I think esmock cannot practically solve this issue.

node's native module resolution will throw an error when it fails to locate the package. esmock's loader only return a different 'vue' definition, but the 'vue' package would still need to be present

import {h} from 'vue';

something esmock does to test various test-runners and packages is, setup special test directories where packages like vue are downloaded and installed. eg like this https://github.com/iambumblehead/esmock/blob/master/tests/tests-jest/package.json this folder downloads jest and related things specifically for unit-tests

[iambumblehead]

another suggestion one could try, write a file like this before running the test "./node_modules/vue/index.js" this would probably be resolved as a cjs module, by node, which would make the error go away

[cawa-93]

@iambumblehead This loader works for me in node v16.14.0

import module from 'module'

// Resolve unexisting package
export async function resolve(specifier, context, nextResolve) {
  if (specifier === 'vue') {
    return {
      shortCircuit: true,
      url: specifier
    };
  }
  return nextResolve(specifier, context);
}

// Load unexisting package
export function load(url, context, nextLoad) {
  if (url === 'vue') {
    return {
      format: 'module',
      shortCircuit: true,
      source: `export const h = (...args) => args`, // <- moke code
    }
  }

  return nextLoad(url, context);
}

[iambumblehead]

@cawa-93 awesome ok let's try to update esmock. Do you need a solution now or is it ok if day or two go by before changes are made?

[iambumblehead]

@cawa-93 thanks for ignoring my earlier statements and finding that solution. If you're interested to try making a PR, from esmock's root folder use npm install && npm run test:install to fetch all dependencies needed, then from whichever test folder is being used, npm test will run tests.

[iambumblehead]

the soonest I could look into this myself is maybe 7 or 8 hours from now

[cawa-93]

Ok. I will try to make pr ASAP. A few days, I think

[iambumblehead]

@cawa-93 if there is a PR with passing tests it can be merged and published as soon as its ready

[cawa-93]

After thinking again, I think I won't find enough time to figure it out and make a change. In any case, you can do it faster (although, personally, these changes are not urgent for me). Therefore, I will leave PR to you. Thanks again for the quick response.

[iambumblehead]

@cawa-93 please confirm if this resolves the issue for you https://github.com/iambumblehead/esmock/releases/tag/v1.9.7

if you think the interface should be changed or have any criticisms or suggestions feel free to give your opinion

[cawa-93]

@iambumblehead It's work like a charm ✨ Thanks
Did you forget to add a new isPackageNotFoundError parameter to the type declaration?

esmock/src/esmock.d.ts

Lines 22 to 25 in 968b357

	interface Options {
	partial?: boolean | undefined;
	purge?: boolean | undefined;
	}

[iambumblehead]

@cawa-93 yes I did forget