Plugins: Plugin Alias v3 throws error

[matt3224]

• Rollup Plugin Name: Alias
• Rollup Plugin Version: 3.0.1
• Rollup Version: 1.31.0
• Operating System (or Browser): macOS 10.15.3
• Node Version: 13.8.0

How Do We Reproduce?

https://repl.it/repls/WatchfulUnsightlyStruct

Expected Behavior

Expect to compile as per v2.2.0

Actual Behavior

Throws mysterious error (plugin alias) TypeError: Cannot read property 'input' of undefined

Thanks!

[bennypowers]

I'm able to avoid this error with:

plugins: [
    customResolver,
    alias({ entries: importAliases, customResolver })
]

As a user, I may have expected alias to cover all cases of resolve

[matt3224]

@bennypowers It seems that your workaround is good, will shout if i run into anything.

Thanks!

[pkit]

It's not a workaround, because it just disables aliasing in a general case.
Alias should come before node-resolve.
Example in README changed to one that actually woks:

// rollup.config.js
import alias from '@rollup/plugin-alias';
import resolve from '@rollup/plugin-node-resolve';

const customResolver = resolve({
  extensions: ['.mjs', '.js', '.jsx', '.json', '.sass', '.scss']
});
const projectRootDir = path.resolve(__dirname);

const config = {
  // ...
  plugins: [
    alias({
      entries: [
        {
          find: 'src',
          replacement: path.resolve(projectRootDir, 'src')
          // OR place `customResolver` here. See explanation below.
        }
      ],
      customResolver
    }),
    resolve()
  ]
};
customResolver.buildStart(config);
export default config

[shellscape]

@pkit thanks for confirming. We're going to close citing that comment. If the example in the readme doesn't work for anyone else, please drop a comment here.

[vladshcherbin]

Example from docs doesn't work. Workaround from https://github.com/rollup/plugins/issues/203#issuecomment-605818790 works, even if @rollup/plugin-node-resolve is placed after alias:

const nodeResolve = resolve()

plugins: [
  alias({
    entries: { ... },
    customResolver: nodeResolve
  }),
  nodeResolve
]

However, it feels more like a hack than a solution.

[pkit]

Workaround doesn't work for any node_modules alias.
I.e. my case: use 'react-dom': 'react-dom/profiling' alias
With or without alias the output is the same if placed after node-resolve

[shellscape]

@vladshcherbin previous commenter indicates that's not so. unless someone can pinpoint why it's not working a positive assertion that it does work is going to take precedent.

[vladshcherbin]

@pkit didn't test it with node_modules alias, only local ones.

Anyway, this issue shouldn't be closed as it's clearly not working for many users following example from current docs. This is the reason we all came to this issue 😉

[shellscape]

I'll reopen if someone can provide an updated reproduction. The repro provided on the original post doesn't run.

[pkit]

@shellscape it's easy to pinpoint why it's not working: when placed after node-resolve alias is working on resolved paths and not on original. i.e. react-dom?commonjs-proxy
But I'm nor sure I need to tell it to you. After all I'm not the author of rollup

[shellscape]

@pkit I'm not the author of Rollup or the alias plugin either. I'm a contributor and team member for maintaining the plugins. Because of the volume of issues we get here we just need reproductions so we don't spend time on trying to recreate the issues folks report.

[pkit]

@shellscape cool, anyway. It seems like combination of node-resolve and commonjs makes it not resolvable in a generic case.
I suppose adding more hacks to alias can help.
here: https://github.com/rollup/plugins/blob/ee5be6a7d8709e42821f6aeabbcad18a4af4dc66/packages/alias/src/index.ts#L90

 else if (
        typeof options.customResolver === 'object' &&
        typeof options.customResolver!.resolveId === 'function'
      )

[vladshcherbin]

@shellscape here's reproduction - https://github.com/vladshcherbin/rollup-alias-error, latest alias version (3.1.0), docs example. Run with yarn build (or npm)

Screenshot

[pkit]

You know what, it looks like a rollup bug.
buildStart() should run before resolveId() but it looks like that it runs after.
Otherwise there won't be an error in the first place, no matter the order

[pkit]

@vladshcherbin it all comes to that issue again https://github.com/rollup/rollup/issues/2826
Really...

[matt3224]

https://repl.it/repls/AttachedWhimsicalDehardwarization

Take a look in here, head into src/main.js and switch the two import lines to see the issue

[shellscape]

Thanks!

[jasonkarns]

Also reproduces when customResolver is at the entry level:

  plugins: [
    alias({
      entries: [{
        find: '@optimizely/optimizely-sdk',
        customResolver: resolve({browser: false})
      }]
    }),
    resolve({ browser: true })
  ]

[lukastaegert]

What needs to happen is that node-resolve should keep the resolveId hook in a pending promise state until its own buildStart hook has run. Adding more hooks will not really solve anything, just add more combinatorics to make issues less likely and more complicated. I think that case is an important gotcha that we should also add to the official Rollup docs

[shellscape]

@lukastaegert that's a little outside of my wheelhouse. would you be able to POC that? I might be able to take it from there.

[lukastaegert]

Actually on second thought I think there might be a much simpler solution that would be inside Rollup and not require any plugin to change: We just make sure that this.resolve and similar plugin context functions do not trigger any hooks synchronously. Then as all buildStart hooks are started together, each plugin will have a chance to pick up Rollup's option before any other hook is triggered for the first time. Will try it out later and publish a fix if this works out as I think.

[pkit]

What needs to happen is that node-resolve should keep the resolveId hook in a pending promise state until its own buildStart hook has run. Adding more hooks will not really solve anything, just add more combinatorics to make issues less likely and more complicated. I think that case is an important gotcha that we should also add to the official Rollup docs

Yup. That's what I did in the end. It also kind of ugly looking. But better.

[lukastaegert]

Ok, the problem is quite a different one than I thought, it is in a way what was already posted here: https://github.com/rollup/plugins/issues/203#issuecomment-618523678
The idea of just running a rollup plugin outside Rollup, i.e. node-resolve just used as a customResolver, is a rather bad one, because the buildStart hook cannot be triggered for that plugin. And that is not surprising if the plugin is not used as a Rollup plugin but just as a function.

At the moment, this only concerns the buildStart hook, so what the plugin should actually do I guess is in its own buildStart hook to check if any custom resolvers have a buildStart hook and run them manually.

[lukastaegert]

I can try to set up a PR.

[lukastaegert]

fix at #426

[bennypowers]

For the record, I resolved this problem once and for all by compiling aliases out-of-band using ttsc. This also bought me a nice build-time reduction.

[pkit]

@bennypowers can you expand on that? What exactly was compiled?

[bennypowers]

@pkit sure thing. This solution will only work for users writing typescript sources who are willing to run a wrapper around tsc. It's not a solution to this thread's core problem. I'm only posting it here to help ~my future self~ people who land here from google

So my use case is to alias module like

import '#components/card`

instead of

import '../../../card/card.ts

I had been:

• running @rollup/plugin-typescript to compile and build at the same time
• using @rollup/plugin-alias to resolve module specifiers that start with #

There were two downsides:

1. builds were taking 2-5 minutes
2. I had to maintain my module aliases both in tsconfig.json's paths field, as well as in rollup config

My ultimate solution was to use ttypescript with this in tsconfig:

{
  "compilerOptions": {
    "plugins": [
      { "transform": "@zerollup/ts-transform-paths" }
    ]
}

As well as doing a two-step build:

1. compile ts sources using ttsc (no typo)
2. run rollup on the compiled javascript files.

Those steps solved both the performance (builds down to 30-40 seconds) and maintenance (aliases handled exclusively by typescript) problems.

[pkit]

@bennypowers cool. Thanks!
Unfortunately my use case is totally dynamic (I don't need aliases all the time, only for specific build options).
And if my builds were 2 min I would shoot myself anyway... :)