Let the compiler shout at me on typeerrors:

[NobbZ]

I expect the following snippet to barf at me before even trying to execute the tests:

class HelloWorld {
    static hello(name = "World" : string): number {
        return "Hello, " + name + "!"
    }
}

export default HelloWorld

Instead of barfing, yarn test && yarn lint just complains about string beeing a variable name which clashes with a built in type:

yarn test v0.22.0
$ jest --no-cache
 PASS  ./hello-world.test.ts
  Hello World
    ✓ says hello world with no name (2ms)
    ✓ says hello to bob (1ms)
    ✓ says hello to sally

Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        1.063s
Ran all test suites.
Done in 1.79s.
yarn lint v0.22.0
$ tslint '*.ts?(x)'; exit 0

hello-world.ts[2, 35]: variable name clashes with keyword/type
Done in 0.48s.

So currently, in how the tests are run, it seems as if typescript is just another typeless hell around javascript. Therefore the request to do the following:

• Make the compiler fail on type errors (absolute minimum)
• Make the compiler (or the linter) warn or error (the former is totally enough I think) on missing types

[NobbZ]

PS: totally the same behaviour when s/string/number/

[NobbZ]

OK, in the meantime I was able to find out, that tsc will complain about a syntax error:

hello-world.ts(2,33): error TS1005: ',' expected.

After some googling I found that correct syntax for the class were:

class HelloWorld {
    static hello(name: number = "World"): number {
        return "Hello, " + name + "!"
    }
}

compiling this, now successfully complains about types beeing incorrect:

hello-world.ts(2,18): error TS2322: Type '"World"' is not assignable to type 'number'.
hello-world.ts(3,9): error TS2322: Type 'string' is not assignable to type 'number'.
hello-world.test.ts(11,29): error TS2345: Argument of type '"Bob"' is not assignable to parameter of type 'number'.
hello-world.test.ts(15,29): error TS2345: Argument of type '"Sally"' is not assignable to parameter of type 'number'.

Therefore I have to assume, that the typescript-track currently doesn't even use typescript!

[masters3d]

Good point. I filed a bug/feature question.
As a work around we could run the compiler every time we run the tests to catch this
"test": "tsc -p . && jest --no-cache",
I do think since ts-jest compiles the code before running jest that they should display any errors from the compiler and fail.

[NobbZ]

You filed a bug/feature where? Do you have a link/crossref?

[masters3d]

kulshekhar/ts-jest#250

[NobbZ]

Also, a better way to alter the script line seems to be: tsc --noEmit -p . && jest --no-cache.

This way there is no javascript generated which leads to running the tests twice by jest

[masters3d]

What rabbit hole. Others are also using --noEmit. I think that is what we are going to use too: ds300/react-native-typescript-transformer#13

[thedevelopnik]

@masters3d thanks for doing that PR! Looks like a good solution.

And thanks for catching this @NobbZ. Just implemented the tsc --noEmit in my own copy of the exercises and found out my Hello World solution didn't pass anymore hah.