Typescript compile errors don't cause build failure

[rsheasby]

Describe the bug
When using svelte-preprocess for typescript, a TS compilation error does not abort the build, and results in the bundle still being created, as well as a successful status code being returned.

This is especially a problem for verifying that something builds correctly in CI scripts.

Logs
You can see an example here with a syntax error in a typescript style tag:

rsheasby@Ryan-Mac ~/D/b/client (6-registration-email)> npx rollup -c
src/main.js → public/build/bundle.js...

src/App.svelte:7:14 - error TS1005: '=' expected.
7 import Bulma ;from './Bulma.svelte';

~

src/App.svelte:7:15 - error TS2304: Cannot find name 'from'.
7 import Bulma ;from './Bulma.svelte';

~~~~

src/App.svelte:7:20 - error TS1005: ';' expected.
7 import Bulma ;from './Bulma.svelte';

~~~~~~~~~~~~~~~~
created public/build/bundle.js in 8s

rsheasby@Ryan-Mac ~/D/b/client (6-registration-email)> echo $status

0

As you can see, the bundle is still written and the status code is 0.
When doing the same build with a javascript style tag(thereby removing the preprocess step), the build fails and returns status code 1 as expected.

To Reproduce
Setup boilerplate svelte with rollup, add svelte-preprocess for typescript, and add a syntax error to a typescript script tag.

Expected behavior
Rollup should fail and return a bad status code when a preprocessor fails

Information about your project:
Examples provided from macOS Catalina with rollup v2.16.11 and svelte-preprocess v3.9.7.
Has been confirmed on various Linux systems too.

[kaisermann]

Hey @rsheasby 👋 Thanks for the report! It does indeed make sense to throw an error if the ts compiler finds some error. I've added it to v3.9.9 🎉

[ansavchenco]

Looks like the issue is still present in 4.6.1 when Snowpack is used as a bundler.

[dubiousandrew]

I have this issue with 4.5.2 and just upgraded to 4.6.5 and still have this problem.

[kaisermann]

@dubiousandrew Are you also using Snowpack?

[jbrunton]

@kaisermann: I'm still seeing this with the default Svelte typescript template, using Rollup. Example repo here: https://github.com/jbrunton/svelte-ts-error-example/

Repo was created like so:

npx degit sveltejs/template svelte-ts-error-example
cd svelte-ts-error-example
node scripts/setupTypeScript.js

Then I added a line to main.ts which doesn't type check.

Build output:

npm run build

> svelte-app@1.0.0 build /Users/john/git/svelte-ts-error-example
> rollup -c


src/main.ts → public/build/bundle.js...
(!) Plugin typescript: @rollup/plugin-typescript TS2322: Type 'string' is not assignable to type 'number'.
src/main.ts: (10:7)

10 const x: number = "1";
         ~

(!) Plugin typescript: @rollup/plugin-typescript: Typescript 'sourceMap' compiler option must be set to generate source maps.
created public/build/bundle.js in 1.2s
$ echo $?
0

svelte-preprocess version is the latest (4.7.2).

[ItzaMi]

Hey 👋 Created a new project on Svelte following the steps on the homepage:

npx degit sveltejs/template my-svelte-project
node scripts/setupTypeScript.js

yarn
yarn run dev

And I get TypeScript errors on my code but on build (or even on yarn run dev) I have no error messages. What might be happening here?
sourceMap is set to true

[kaisermann]

@kaisermann: I'm still seeing this with the default Svelte typescript template, using Rollup. Example repo here: https://github.com/jbrunton/svelte-ts-error-example/

Repo was created like so:

npx degit sveltejs/template svelte-ts-error-example
cd svelte-ts-error-example
node scripts/setupTypeScript.js

Then I added a line to main.ts which doesn't type check.

Build output:

npm run build

> svelte-app@1.0.0 build /Users/john/git/svelte-ts-error-example
> rollup -c


src/main.ts → public/build/bundle.js...
(!) Plugin typescript: @rollup/plugin-typescript TS2322: Type 'string' is not assignable to type 'number'.
src/main.ts: (10:7)

10 const x: number = "1";
         ~

(!) Plugin typescript: @rollup/plugin-typescript: Typescript 'sourceMap' compiler option must be set to generate source maps.
created public/build/bundle.js in 1.2s
$ echo $?
0

svelte-preprocess version is the latest (4.7.2).Ï

This is expected since we don't do any kind of type-checking. Your TS code is just transpiled to JS.

Hey 👋 Created a new project on Svelte following the steps on the homepage:

npx degit sveltejs/template my-svelte-project
node scripts/setupTypeScript.js

yarn
yarn run dev

And I get TypeScript errors on my code but on build (or even on yarn run dev) I have no error messages. What might be happening here?
sourceMap is set to true

Hey, @ItzaMi 👋 I couldn't reproduce it with the commands that you typed.

[kaisermann]

We won't be throwing type-related errors as we only transpile TS code into JS.