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Parcel 2: TypeScript automatic zero configuration not type checking or reading tsconfig.json

See original GitHub issue

I’ve been following #1378 for a long time, and I’m thrilled to see Parcel 2 taking on better first-class support for TypeScript. There’s currently some problems with Parcel 2 out of the box, and I didn’t see any threads tracking this, so I’m making an issue.

🐛 bug report

In 2.0.0-alpha.3.2, given a very basic TypeScript project, there are three issues:

the typescript package is not automatically installed
settings in tsconfig.json are completely ignored
typescript errors are silently ignored and compiled anyway

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

Here’s all of the files:

package.json created from two commands:
- yarn init -y
- yarn install -D parcel@v2

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>My First Parcel App</title>
    <script src="index.ts"></script>
  </head>
  <body>
    <h1>Hello, World!</h1>
  </body>
</html>

index.ts

console.log("Hello, von Nuemann!")
const failMe: BadType = 5; // this should fail, but it compiles

optionally, I added a junk tsconfig.json to test, and it’s obviously being ignored because parcel still compiles:
```
{
  ALDIFJ SLDIFJ :LEIRJ LWEIJR;
}}}}}
  "compilerOptions": {
```

🤔 Expected Behavior

As part of parcels “zero configuration”, parcel automatically detects TypeScript and configures the project to correctly use TypeScript.

TypeScript compilation or validation should fail by default when there are type errors
typescript package should be installed automatically
tsconfig.json should be read and used by whatever is compiling it, if it exists

😯 Current Behavior

the typescript package is not automatically installed
settings in tsconfig.json are completely ignored
typescript errors are silently ignored and compiled anyway

💁 Possible Solution

I’m guessing one of these two potential solutions:

The current default transformer-babel is correctly configured to behave as expected with TypeScript, extending from #3083
typescript and @parcel/transformer-typescript(-tsc?) is automatically installed when Parcel 2 detects a .ts file.

Either one is fine, I think, as long as the TypeScript compilation actually behaves like TypeScript by default!

🔦 Context

Seems to have started in this PR that defaults to babel for TypeScript: https://github.com/parcel-bundler/parcel/pull/3083
Type checking seems to have been merged, but it’s not happening: https://github.com/parcel-bundler/parcel/pull/3232

💻 Code Sample

See files above

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-alpha.3.2
Node	v10.15.3
npm/Yarn	1.21.1
Operating System	Mac 10.14.6

Issue Analytics

State:
Created 4 years ago
Reactions:121
Comments:84 (32 by maintainers)

Top GitHub Comments

130reactions

bbughcommented, Jan 21, 2020

I’m quite confused by that position. If the official stance is that external tools should be used for handling compilation errors, why does Parcel report errors for other compilers, like sass? Sass is a superset of CSS with a compiler, much like TypeScript is a superset of JavaScript with a compiler. It seems like you’re looking at TypeScript as if it’s a linter instead of a separate language with separate compilation and configuration needs.

I propose that TypeScript is treated as a first-class zero-configuration part of Parcel’s bundler, using the real Microsoft TypeScript compiler by default, with full type checking in the bundling process. No external tools required, it’s just drop in a ts file and the appropriate libraries are added and run.

If people want to use babel for whatever reason, that could be configured in parcelrc. Not every project that uses TypeScript will want to use Babel, especially because Babel doesn’t support the full TypeScript language spec.

Thank you for opening this up for dialogue so the community can comment.

91reactions

DeMoorJaspercommented, Jan 20, 2020

Our opinion was that your IDE should catch typing errors when developing and on deploy using a CI/CD service it should be a step before even starting up anything (including Parcel) to speedup the process, similar to how you’d do linting. Typing fails, don’t run build/tests/…

I’ve also been using typescript for a couple years and have never had the need to have parcel throw validation errors the IDE integration works fine for most cases.

In my opinion this should never be considered a bug, it’s just a different opinion. The default might change though, especially as we have full freedom as it’s still alpha.

I didn’t know vue couldn’t be typechecked using tsc. This is pretty convincing to change the default… although the spam in dev mode is pretty annoying but probably the point of having types I guess.

On a positive note the validations only run after Parcel fully completed so you never have the annoying issue that you can’t look at a change without fixing the types. It does however return an error in production mode so a properly configured CI/CD pipeline would not deploy…

I’ll flag this as an RFC, seems more fitting than question or bug. Would be cool to do a poll on this or something at some point.