Prevents exiting the process on sigint in case of yarn run, fixes #8895.

[mdevils]

Prevents exiting the process on SIGINT in case of yarn run.

Current behavior:

When user presses ctrl+C yarn exits immediately and shell prompt is shown. If a run script needs some time to cleanup before exit and outputs something to terminal, it pollutes the prompt.

New behavior:

yarn doesn't make any decisions on when to exit, it just waits for the children.
Works the same as npm run now in that regard.

This PR fixes this issue: #8895

Test cases

Test script for this PR: example.js

const EXIT_CODE = 1;

setInterval(() => {
    console.log('tick');
}, 1000);

process.on('SIGINT', () => {
    console.log('SIGINT from script');
    setTimeout(() => process.exit(EXIT_CODE), 3000);
});

Regular case

Excerpt from package.json:

                "example": "node example.js",

Actual behavior with this script:

bash-3.2$ yarn run example
yarn run v1.22.22
$ node example.js
tick
tick
^CSIGINT from script

bash-3.2$ tick
tick
tick

New behavior with this script:

bash-3.2$ yarn example
yarn run v1.23.0-0
$ node example.js
tick
tick
^CSIGINT from script
tick
tick
tick
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
bash-3.2$

For reference, npm run behavior:

bash-3.2$ npm run example

> example
> node example.js

tick
tick
^CSIGINT from script
tick
tick
tick
bash-3.2$

Using pre/post scripts

Excerpt from package.json:

                "preexample": "node example.js",
                "example": "node example.js",
                "postexample": "node example.js"

Actual behavior with this script:

bash-3.2$ yarn example
yarn run v1.22.22
$ node example.js
tick
tick
^CSIGINT from script

bash-3.2$ tick
tick
tick

New behavior with this script:

bash-3.2$ yarn example
yarn run v1.23.0-0
$ node example.js
tick
tick
^CSIGINT from script
tick
tick
tick
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
bash-3.2$

For reference, npm run behavior:

bash-3.2$ npm run example

> preexample
> node example.js

tick
tick
^CSIGINT from script
tick
tick
tick
bash-3.2$

Using pre/post scripts with zero exit code

Excerpt from package.json:

                "preexample": "node example.js",
                "example": "node example.js",
                "postexample": "node example.js"

Modify example.js and set EXIT_CODE to 0.

Actual behavior:

bash-3.2$ yarn example
yarn run v1.22.22
$ node example.js
tick
tick
^CSIGINT from script

bash-3.2$ tick
tick
tick

New behavior:

bash-3.2$ yarn example
yarn run v1.23.0-0
$ node example.js
tick
tick
^CSIGINT from script
tick
tick
tick
$ node example.js
tick
tick
^CSIGINT from script
tick
tick
tick
$ node example.js
tick
tick
^CSIGINT from script
tick
tick
tick
✨  Done in 16.77s.
bash-3.2$

For reference npm behavior:

bash-3.2$ npm run example

> preexample
> node example.js

tick
tick
^CSIGINT from script
tick
tick
tick

> example
> node example.js

tick
tick
^CSIGINT from script
tick
tick
tick

> postexample
> node example.js

tick
tick
^CSIGINT from script
tick
tick
tick
bash-3.2$