Typescript 2.9.1 strange errors with imports not getting resolved

[ascott18]

Version

3.0.0-beta.15

Reproduction link

https://github.com/ascott18/vue-cli-ts291-bug

Steps to reproduce

• yarn
• yarn serve
• Navigate to site, open F12 tools, observe errors:

What is expected?

Import Consts should be resolved by webpack and should function as any other import would. Instead, webpack doesn't change this import to the usual WEBPACK_IMPORTED_MODULE stuff - it stays as Consts, which is undefined in the compiled javascript.

Note that this issue also happens if the import of Consts is changed to import { Foo } from './imported-const' and the corresponding usage is changed accordingly.

What is actually happening?

vue.runtime.esm.js?2b0e:587 [Vue warn]: Error in mounted hook: "ReferenceError: Consts is not defined"

found in

---> <App> at src\App.vue
       <Root>
warn @ vue.runtime.esm.js?2b0e:587

vue.runtime.esm.js?2b0e:1737 ReferenceError: Consts is not defined
    at new DerivedFoo (App.vue?95a9:16)
    at VueComponent.mounted (App.vue?95a9:25)
    at callHook (vue.runtime.esm.js?2b0e:2917)
    at Object.insert (vue.runtime.esm.js?2b0e:4154)
    at invokeInsertHook (vue.runtime.esm.js?2b0e:5956)
    at Vue.patch [as __patch__] (vue.runtime.esm.js?2b0e:6175)
    at Vue._update (vue.runtime.esm.js?2b0e:2656)
    at Vue.updateComponent (vue.runtime.esm.js?2b0e:2784)
    at Watcher.get (vue.runtime.esm.js?2b0e:3138)
    at new Watcher (vue.runtime.esm.js?2b0e:3127)
    at mountComponent (vue.runtime.esm.js?2b0e:2791)
    at Vue.$mount (vue.runtime.esm.js?2b0e:7995)
    at eval (main.ts?cd49:8)
    at Module../src/main.ts (app.js:1387)
    at __webpack_require__ (app.js:717)
    at fn (app.js:99)
    at Object.0 (app.js:1400)
    at __webpack_require__ (app.js:717)
    at app.js:784
    at app.js:787

---

Typescript 2.9.1 suffers from this; downgrading to 2.8.3 fixes this error. See https://github.com/ascott18/vue-cli-ts291-bug/tree/ts-283.

If I pull the code in question out of a .vue file and into a plain .ts file and then compile it on its own with tsc, the compiled output is identical between 2.8.3 and 2.9.1. This seems to indicate that it isn't a bug specifically with Typescript, but somewhere in the toolchain's interactions with Typescript.

[LinusBorg]

Sounds rather related to this bug with Typescript:

microsoft/TypeScript#24551

Currently I'm having an issue where I've imported a variable, and the import is being removed during transpilation. The reference still remains, but the code breaks at runtime because the import is missing.
[...]
the issue is currently occurring when an imported reference is used only in super clause of a constructor.

(emphasis by me)

You do exactly that:

import * as Consts from './imported-const'
class DerivedFoo extends BaseFoo<any> {
  constructor() { super(Consts.Foo) }
}

They already merged a fix, so I assume 2.9.2 should have a fix for this.

Thanks for the detailed reporduction by the way!

[ascott18]

That looks like exactly the issue. Thanks for taking a look! I'll let you close this one out as you see fit; not sure if you wanted to leave it open to track the bump to 2.9.2 when it comes out.

[LinusBorg]

We'llleave it open to track it.

[LinusBorg]

2.9.2 is out with the fix.

I'll close this, we can open a fresh issue if it persists for whatever reason