Can not use custom transfom by runCLI

[fattydevelop]

Do you want to request a feature or report a bug?
BUG
What is the current behavior?
can not use transform api like other api do.

jestCli.runCLI(
        {
            transform: {
                '^.+\\.jsx?$': require.resolve('../configs/jest.transform.js')
            },
            transformIgnorePatterns: ['/3333/'],
            testMatch: ['<rootDir>/test/*.js?(x)'],
            slient: false,
            cache: false,
            debug: true
        },
        [cwd],
        function(success) {
            console.log(success);
        }
    );

here's custom transform define.

const babelConfig = require('./babel');
module.exports = require('babel-jest').createTransformer(babelConfig);

when I console the jest debug info there's no key of transform . And also transform can't work.

What is the expected behavior?

transform

Please provide your exact Jest configuration and mention your Jest, node,
yarn/npm version and operating system.
node 8.9.4 npm 5.6.0 jest-cli ^22.1.4

thanks for help.

[fattydevelop]

I have found the solution by search source code .

For transform set loadUtils use isJSONString to validate config. So I must stringify before use.

transform: JSON.stringify({'^.+\\.jsx?$': require.resolve('../configs/jest.transform.js')})

I guess other object setting also need stringify before use. I'll close this issue by case, but it's really confused to stringify a config. BTW, do we have a chance to modify it or it's by design ?

[o-alexandrov]

Still the case, even for the latest jest 27.0.0-next.7.

• using JSON.stringify(...) is required to pass transform option to runCLI

Apologies for pinging; please, consider to reopen @SimenB

[SimenB]

Jest does not have a public programmatic API, you can track #5048.

[github-actions]

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