v2: "Got unexpected null" when building TypeScript project #3690

magcius · 2019-10-27T19:50:05Z

🐛 bug report

When trying to upgrade my project to Parcel V2, I got the error message:

$ D:\Development\NITRO_BMD\node_modules\.bin\parcel build src/index.html
× Got unexpected null
    at nullthrows (D:\Development\NITRO_BMD\node_modules\nullthrows\nullthrows.js:7:15)
    at BundleGraph.resolveSymbol (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\BundleGraph.js:368:53)
    at BundleGraph.resolveSymbol (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\public\BundleGraph.js:116:51)
    at markUsed (D:\Development\NITRO_BMD\node_modules\@parcel\scope-hoisting\lib\concat.js:201:32)
    at enter (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\Graph.js:475:16)
    at enter (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\Graph.js:475:16)
    at enter (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\Graph.js:475:16)
    at walk (D:\Development\NITRO_BMD\node_modules\@parcel\core\lib\Graph.js:331:22)
⠹ Optimizing index.19203168.css...
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

🎛 Configuration (.babelrc, package.json, cli command)

The project is available here: https://github.com/magcius/noclip.website/tree/parcel-v2

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-alpha.2.1
Node	v10.16.3
npm/Yarn	Yarn version 1.19.0
Operating System	Windows 10

The text was updated successfully, but these errors were encountered:

mischnic · 2019-10-27T20:01:31Z

Very likely the same bug as #3640. (Also using @sentry/browser)

magcius · 2019-10-27T20:16:05Z

Thanks. I removed the sentry package for now, and updated the parcel-v2 branch with the removal. I am now hitting another error:

PS D:\Development\NITRO_BMD> yarn parcel build src\index.html
yarn run v1.19.0
$ D:\Development\NITRO_BMD\node_modules\.bin\parcel build src\index.html
× src\gfx\platform\GfxPlatformImpl.ts does not export 'GfxBindings'
    at replaceExportNode (D:\Development\NITRO_BMD\node_modules\@parcel\scope-hoisting\lib\link.js:149:13)
    at ReferencedIdentifier (D:\Development\NITRO_BMD\node_modules\@parcel\scope-hoisting\lib\link.js:511:20)
    at newFn (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\visitors.js:216:17)
    at NodePath._call (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\path\context.js:53:20)
    at NodePath.call (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\path\context.js:40:17)
    at NodePath.visit (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\path\context.js:88:12)
    at TraversalContext.visitQueue (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\context.js:112:16)
    at TraversalContext.visitSingle (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\context.js:84:19)
    at TraversalContext.visit (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\context.js:140:19)
    at Function.traverse.node (D:\Development\NITRO_BMD\node_modules\@babel\traverse\lib\index.js:80:17)
⠧ Optimizing index.ee239b95.js...
error Command failed with exit code 1.

I don't know why it thinks that GfxBindings is not exported, when it clearly is.

Is there a way to turn scope hoisting off for now? All I could find was this, which implies it should be off by default: https://github.com/parcel-bundler/parcel/blob/v2/packages/core/parcel-bundler/src/Bundler.js#L110-L111

mischnic · 2019-10-27T20:26:29Z

Is there a way to turn scope hoisting off for now? All I could find was this, which implies it should be off by default: /packages/core/parcel-bundler/src/Bundler.js@v2#L110-L111

--no-scope-hoist

(Even in the v2 branch, packages/core/parcel-bundler is the v1 version)

parcel-bundler/parcel#3690

magcius · 2019-10-27T20:37:06Z

Thank you, I've disabled scope hoisting for now, which seems to have solved my problem. If you intend to look into the scope hoisting issues, please let me know if you need any help setting up the repo for a repro case.

mischnic · 2019-10-27T22:59:03Z

× src\gfx\platform\GfxPlatformImpl.ts does not export 'GfxBindings'

Actually, the output from typescript for

export enum _T { Buffer, Texture, ColorAttachment, DepthStencilAttachment, Sampler, Program, Bindings, InputLayout, InputState, RenderPipeline };

interface GfxResourceBase { ResourceName?: string, ResourceUniqueId: number };
export interface GfxBuffer extends GfxResourceBase { _T: _T.Buffer };
export interface GfxTexture extends GfxResourceBase { _T: _T.Texture };
// ...
export type GfxResource =
    GfxBuffer | GfxTexture | GfxColorAttachment | GfxDepthStencilAttachment | GfxSampler | GfxProgram | GfxBindings | GfxInputLayout | GfxInputState | GfxRenderPipeline;

is

export var _T;
(function (_T) {
    _T[_T["Buffer"] = 0] = "Buffer";
    _T[_T["Texture"] = 1] = "Texture";
// ...
})(_T || (_T = {}));

~~Not even sure what the expected output is here (what is needed at runtime). But from Parcel's perspective, there is no GfxBindings ES6 named export.~~

I'm kind of surprised that works without scope hoisting. How does TS know that another modules exports aren't really named exports but an object property in a named export _T.

TS playground, and Babel doesn't support this at all? REPL

magcius · 2019-10-27T23:06:20Z

Interfaces are not a thing that have any runtime equivalent. They only exist in the typesystem.

mischnic · 2019-10-27T23:11:09Z

I see, but Typescript can't know that

import { GfxDevice, GfxBufferUsage, GfxBuffer, GfxInputState, GfxFormat, GfxInputLayout, GfxProgram, GfxBindingLayoutDescriptor, GfxRenderPass, GfxBindings, GfxHostAccessPass, GfxVertexAttributeFrequency } from '../gfx/platform/GfxPlatform';

need to be completely removed with the typescript.transpileModule api (which processes every asset individually).

Flow has import type {...} for something like that. I don't know how Typescript solves this issue (related: #3624).

magcius · 2019-10-27T23:33:15Z

I don't know why babel REPL has issues with enums: https://babeljs.io/repl#?babili=false&browsers=IE%2011&build=&builtIns=false&spec=false&loose=false&code_lz=KYOwrgtgBAolDeUCGAaKAjNBjKBfA3AFBA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=false&presets=typescript%2Cenv&prettier=false&targets=&version=7.6.4&externalPlugins=%40babel%2Fplugin-proposal-export-default-from%407.5.2

But offline, it can compile it just fine. I assume it just can't parse TypeScript online.

I don't know what exactly transpileModule does, but I assume it just ignores interfaces and doesn't emit them in the output, since it doesn't need to do any work to verify them. Note how it doesn't bother emitting the interfaces here: https://www.typescriptlang.org/play/index.html#code/JYWwDg9gTgLgBAbzgYQuCA7AphmAaOAJSwEMBjGAOQgBMsBBKKEgTzgF84AzKNOAciikK-ANwAocWQA2JAM5y4AMQgQ4WAB4wcNRanTZcicXFNwwAVwBG04GTgQrAKywU5ALiLCqtBk1YA2gC6cAC8cMES7OJAA

Why my code is different, I don't know.

mischnic · 2019-10-28T17:14:26Z

I don't know what exactly transpileModule does, but I assume it just ignores interfaces and doesn't emit them in the output, since it doesn't need to do any work to verify them.

They aren't needed at runtime. But the issue here is that Typescript doesn't know if an import is importing a "real" value or an interface (where the export won't exist at runtime).

magcius · 2019-10-28T17:19:52Z

It will know, because an interface is never used except as a type annotation. You cannot declare functions on interfaces, nor construct them with new. They are not allowed in any grammar position that will appear in the transpiled JS, so it's implicit from the usage that the import can be dropped.

GfxBindings should never appear in any transpiled module's output. Why the scope hoisting code is seeing it is the real issue here.

mischnic · 2019-10-28T17:51:31Z

Parcel could work around this Typescript problem by removing unused import specifiers (e.g. GfxBindings) while keeping the import declaration (because of side effects).

But generally, this (the Typescript output) is a violation of the ESM module spec (importing a non-existent export will throw a SyntaxError, it doesn't matter if it's unused).

magcius · 2019-10-28T18:15:28Z

Is the TypeScript output here generating an import for GfxBindings? That sounds like a TSC bug if it is.

mischnic · 2019-10-28T18:18:44Z

Is the TypeScript output here generating an import for GfxBindings?

Yes (which is understandable because every file is transpiled individually and TS can't know if GfxBindings will exist at runtime. They'd have to remove an import if it's only used as a type annotation.)

magcius · 2019-10-28T18:21:04Z

I'll have to investigate later. If you can send me the TSC output or tell me where to find it, that would be a huge help. Not quite sure how to navigate the Parcel cache myself.

magcius · 2019-10-28T18:22:14Z

They'd have to remove an import if it's only used as a type annotation

TSC should be doing this already. See the example I posted above: https://www.typescriptlang.org/play/index.html#code/JYWwDg9gTgLgBAbzgYQuCA7AphmAaOAJSwEMBjGAOQgBMsBBKKEgTzgF84AzKNOAciikK-ANwAocWQA2JAM5y4AMQgQ4WAB4wcNRanTZcicXFNwwAVwBG04GTgQrAKywU5ALiLCqtBk1YA2gC6cAC8cMES7OJAA

mischnic · 2019-10-28T18:46:32Z

Interesting, now the question is where the import isn't removed.

devongovett · 2019-10-28T18:50:44Z

does babel do the same thing (remove type imports)? v2 uses babel to compile typescript by default, not tsc.

mischnic · 2019-10-28T18:51:57Z

@devongovett his parcelrc:

{
    "extends": "@parcel/config-default",
    "transforms": {
        "*.ts": [ "@parcel/transformer-typescript-tsc", "@parcel/transformer-js" ]
    }
}

magcius · 2019-10-28T19:02:34Z

Yes, Babel's TypeScript support chokes on my project currently, so I cannot use it.

Banou26 · 2019-11-15T23:40:45Z

Did anyone find a workaround for this error ?
I'm randomly getting it so i have to find ways to dev around it by not using certain features, which is quite annoying lol.

… the messages, blocked by parcel-bundler/parcel#3690

astegmaier · 2020-02-28T03:07:07Z

I was able to solve this issue by removing two lines:

https://github.com/magcius/noclip.website/blob/c9f19e2206b035b957b63710577948bbb9ea2fb2/src/gfx/platform/GfxPlatform.ts#L324

https://github.com/magcius/noclip.website/blob/c9f19e2206b035b957b63710577948bbb9ea2fb2/src/viewer.ts#L247

(There are additional build errors that appeared after I solved this one, but they appear unrelated - I might be able to fully peel the onion if I have a bit more time).

The problem is that if you re-export types, you thwart typescript's ability to do "import elision" (i.e. detect whether an imported type is just used as a type (and can be removed by the transpiler) or not (and therefore should remain). This is a problem if you're compiling using transpileModules (like @parcel/transformer-typescript-tsc does). Typescript 3.8 added a new feature to allow you to explicitly say that you want to import a thing as a type, which can help work around this.

Assuming that parcel2 will be sticking with transpileModules (or babel, which has the same problem), it would be great if we could think of a way to give more actionable error messages when you hit this.

magcius · 2020-02-28T03:25:09Z

Ah, thank you, that makes sense. Re-exporting a type is a grammar position where types are allowed and can't be elided.

astegmaier · 2020-02-28T19:48:55Z

@DeMoorJasper - I think you can close this because we found the root cause was by-design behavior. I opened #4240 to track the idea of providing more helpful error messages in this case.

Richicratos · 2021-04-22T20:47:54Z

I deleted the .parcel-cache folder and it works!

LukasBombach · 2021-11-12T09:49:08Z

You will also get this error in an isolated module, ie one that does neither import nor export anything

mischnic added 🐛 Bug ✨ Parcel 2 labels Oct 27, 2019

magcius added a commit to magcius/noclip.website that referenced this issue Oct 27, 2019

Disable scope hoisting for now

0d91769

parcel-bundler/parcel#3690

magcius mentioned this issue Oct 27, 2019

v2: Move dist dir out of .parcel-cache #3691

Closed

mischnic added the TypeScript label Oct 27, 2019

Banou26 added a commit to Banou26/EPK that referenced this issue Nov 17, 2019

refactor: 🚧improve the protocol by merging first and last status with…

0a33a40

… the messages, blocked by parcel-bundler/parcel#3690

astegmaier mentioned this issue Feb 28, 2020

Parcel2: Better error messages when you re-export an implicit type. #4240

Open

DeMoorJasper closed this as completed Feb 28, 2020

BetoDl mentioned this issue Apr 22, 2021

I deleted the .parcel-cache folder and it works! #6170

Closed

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v2: "Got unexpected null" when building TypeScript project #3690

v2: "Got unexpected null" when building TypeScript project #3690

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v2: "Got unexpected null" when building TypeScript project #3690

v2: "Got unexpected null" when building TypeScript project #3690

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magcius commented Oct 27, 2019 • edited Loading

🐛 bug report

🎛 Configuration (.babelrc, package.json, cli command)

🌍 Your Environment

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