nyc-config-typescript and decorators

Considering a simple TS file like src/main.ts

function Foo(constructorFunction: Function) {
  console.log('Foo decorator')
}

@Foo
class Main {
  constructor() {
    console.log('Running')
  }
}

new Main();

then trying to instrument it by running:

yarn nyc instrument --compact=false src instrumented

with the following configuration:

"nyc": {
  "extends": "@istanbuljs/nyc-config-typescript",
  "all": true
}

then the result file instrumented/main.ts is not instrumented.

If we comment the @Foo decorator, then the file is instrumented again.

function Foo(constructorFunction: Function) {
  console.log('Foo decorator')
}

// @Foo
class Main {
  constructor() {
    console.log('Running')
  }
}

new Main();

result instrumented/main.ts:

// ...
function Foo(constructorFunction: Function) {
  cov_1eomntdplb.f[0]++;
  cov_1eomntdplb.s[0]++;
  console.log('Foo decorator');
} // @Foo

class Main {
  constructor() {
    cov_1eomntdplb.f[1]++;
    cov_1eomntdplb.s[1]++;
    console.log('Running');
  }
}

cov_1eomntdplb.s[2]++;
new Main();

Am I missing something or is there an issue with decorators?

[wyp0011]

I found that extends will replace parser-plugins in loading nyc config.

So two way to solve this problem.

First one, use parser-plugins and remove extends from your nyc config.

"nyc": {
  "parser-plugins": [
        "typescript",
        "decorators-legacy"
    ]
  "all": true
}

Second one, new nyc-config.js and extends from this file.

'use strict';

const { parserPlugins } = require('@istanbuljs/schema').defaults.nyc;

module.exports = {
    cache: false,
    parserPlugins: parserPlugins.concat('typescript', 'decorators-legacy')
};

"nyc": {
  "extends": "./nyc-config.js",
  "all": true
}

[rishi1117]

hey All, @wyp0011 i have tried the first option that you suggested. That does instrument the .ts files with decorators but it does not work properly. It is giving the issue export is moved before decorators which gives error for compiling

Can anyone please help me with this.