Ts-jest: Function arrow name property.

[Fazendaaa]

Right now I'm using:

node.js: 9.8.0
Jest: 23.4.2
ts-jest: 23.1.3
typescript: 2.9.2

And when trying to doing the following in my *.test.ts files:

const foo = () => 'bar';
console.log(foo.name); // '' -- empty string, not undefined or null

foo has the property name in it but is empty. I've run the same code in a separate *.ts file, just to know whether or not was some .tsconfig setting, but the console prints out 'foo' as expected.

My jest.config.json:

{
    "bail": true,
    "expand": true,
    "verbose": true,
    "useStderr": true,
    "forceExit": true,
    "logHeapUsage": true,
    "collectCoverage": true,
    "testRegex": "(./ci/__tests__/.*| (\\.|/)(test|spec))\\.(jsx?|tsx?)$",
    "transform": {
        "^.+\\.tsx?$": "ts-jest"
    },
    "moduleFileExtensions": [
        "ts",
        "tsx",
        "js",
        "jsx",
        "json",
        "node"
    ],
    "coveragePathIgnorePatterns": [
        "./node_modules/",
        "./dist/"
    ],
    "coverageReporters": [
        "json",
        "lcov",
        "text"
    ],
    "globals": {
        "ts-jest": {
            "enableTsDiagnostics": true
        }
    }
}

Could anyone help me out? Any ideas would help a lot.

note: I've already tried StackOverflow and I really think this is a really good question since after looking around in Google I haven't found anything to help me out, and asking in a closed group would mean that others that someday have the same issues with that won't be able to find anything related to it.

note of a note: The Jest folks told me to talk to you guys.

[huafu]

@Fazendaaa thanks for reporting the issue. I guess you know that, but just to be sure: console.log are swallowed by jest. If they are within a it(...) ot test(...) block, then they should be printed, else I believe jest aren't outputing anything.

Please confirm this is not the case (that you console.log are inside a test(...) block), and if it is, post a link to a minimal repo so we can reproduce the issue and hopefully fix it.

[huafu]

Oh wait, on SO someone answered with the correct answer. Arrow functions are anonymous, so no name.

try this:

const foo = () => 'bar';
console.log(foo.name);
function bar() { return 'foo' };
console.log(bar.name);

UPDATE: I answered too quickly, TS is giving the name as the constant, sorry... but my first answer is still valid ;-)

[Fazendaaa]

@huafu Right now I'm trying a new approach of generating the test functions given.json files that describe the function to be tested. It works passing the function itself and its name as string, but when I tried to remove the string with the function name and use the .name property of the function I ran into this issue.

The problem itself is in line 25, here: https://github.com/Fazendaaa/AnilistBot/blob/master/ci/readMocks.ts, called in line 56 here https://github.com/Fazendaaa/AnilistBot/blob/master/ci/doTesting.ts and this is my first test https://github.com/Fazendaaa/AnilistBot/blob/master/ci/__tests__/utils/parse.test.ts

[huafu]

@Fazendaaa FYI you can link to exact line number by clicking in the margin on github ;-)

[huafu]

Ok so I think it's because transpilation is removing the name. Look at how your source is transpiled to javascript, the function becomes anonymous.

https://www.typescriptlang.org/play/#src=export%20const%20sanitize%20%3D%20(%7B%20message%20%7D%3A%20%7B%20message%3A%20string%20%7D)%3A%20string%20%3D%3E%20message.replace(%2F(%3F%3A%3D%5C(%7C%3A0%7C%3Ao%7C%3A%20o%7C%3A%200)%2F%2C%20'%3A%20o')%3B%0D%0A

[huafu]

So yeah, I'm closing this as it is not ts-jest related.

@Fazendaaa I can't think of any workaround right now, sorry

[huafu]

@Fazendaaa find more info there https://github.com/Microsoft/TypeScript/issues/6433