typescript compilerOptions not reflected

Cypress TypeScript compilator probably do not reflects some of compilerOptions. In my case it looks like e.g. strict is ignored.

I am sure that my tsconfig.json is the one which is used because e.g. I have forgotten "noEmitHelpers": true and it raised errors so I needed to remove it.

It was working with webpack compiler.

Current behavior:

tsconfig.json:

{
    "compilerOptions": {
        "strict": true,
        "noUnusedLocals": true,
        "noUnusedParameters": true,
        "noImplicitReturns": true,
        "noFallthroughCasesInSwitch": true,
        "noImplicitAny": true,
        "strictPropertyInitialization": true,
        "preserveConstEnums": false,
        "target": "es5",
        "lib": ["es5", "dom", "es2015.core", "es2015.promise", "es2015.iterable", "es2015.collection"],
        "types": ["cypress"],
        "sourceMap": true,
        "removeComments": false
    },
    "include": ["**/*.ts"]
}

test:

describe("example", () => {
    it("example", () => {
        let a: boolean | undefined;
        let b: boolean = a;
        console.log(b);
    });
});

VS Code reflects tsconfig.json and shows error:

Type 'boolean | undefined' is not assignable to type 'boolean'.
Type 'undefined' is not assignable to type 'boolean'.ts(2322)

Cypress run doesn’t reflects tsconfig.json and successfully compiles script.

Desired behavior:

Cypress also reflects tsconfig.json and shows error:

Type 'boolean | undefined' is not assignable to type 'boolean'.
Type 'undefined' is not assignable to type 'boolean'.ts(2322)

Versions

4.5.0

[keeema]

I still don’t understand where is the problem in allowing it. I am developer so I should decide whether I prefer faster build or safer build. Web-pack pre-processor is just another unnecessary configuration I have to maintain…

[chrisbreiding]

In regards to the original issue, Cypress now supports most compiler options for spec files, but will continue to only transpile files by default and not type check them for performance reasons, so setting "strict": true will have no effect.

We do not plan to add a global option to configure this, as it can be accomplished through the preprocessor API.