Comments in tsconfig.json

[jonaskello]

• Issue

Typescript allows comments in tsconfig.json. When I started using ts-jest it did not like my comments. I know JSON itself does not allow comments but it would be nice if ts-jest could follow typescript on this.

Specifically I got this error:

SyntaxError: /xxx/src/tsconfig.json: Unexpected token / in JSON at positio
n 67
        at JSON.parse (<anonymous>)

• Expected behavior

Comments OK in tsconfig.json.

• Proposed solution

I think one way to solve it would be to use the tsconfig package that replicates how typescript parses tsconfig.

[kulshekhar]

@jonaskello thank you for reporting this and proposing a solution. The fix is in and has been published.

[jonaskello]

@kulshekhar Thanks for the quick fix, now I can add my comments back in :-).

[jonaskello]

I tested some more and found one case where it does not work. If you have extends in tsconfig.json then it uses regular require, please see this line. So in the base tsconfig comments does not work yet.

[kulshekhar]

@jonaskello thanks again! The fix is in and published

[b3nk3]

This is still broken, when I have a comment in the tsconfig.json and using this:

import type { Config } from 'jest';
import { pathsToModuleNameMapper } from 'ts-jest';
import { compilerOptions } from './tsconfig.json';

const config: Config = {
  moduleNameMapper: {
    ...pathsToModuleNameMapper(compilerOptions.paths, { prefix: '<rootDir>/', useESM: true }),
  },
};

export default config;

[SimonSimCity]

@b3nk3 It works when replacing the import of the json-configuration by a custom solution described in https://stackoverflow.com/a/53898219/517914. According to the author, this should also work when extending the ts-config file.

/** @type {import('ts-jest').JestConfigWithTsJest} */
import type { Config } from 'jest';
import { pathsToModuleNameMapper } from 'ts-jest';
import ts from 'typescript';

const configFileName = ts.findConfigFile('./', ts.sys.fileExists, 'tsconfig.json');
const configFile = ts.readConfigFile(configFileName!, ts.sys.readFile);
const compilerOptions = ts.parseJsonConfigFileContent(configFile.config, ts.sys, './');

const config: Config = {
  moduleNameMapper: pathsToModuleNameMapper(compilerOptions.options.paths!, {
    prefix: '<rootDir>',
  }),
};

export default config;