path-check.ts

import { spawn } from 'child_process';

/**
 * This type is used to bypass the `defaultImpl` when running the tests.
 */
export type ExecForCode = {
    run: (execName: string, args: Array<string>, cwd: string) => Promise<number>;
};

const defaultImpl: ExecForCode = {
    run: (execName: string, args: Array<string>, cwd: string) => {
        return new Promise((resolve, reject) => {
            const options = { cwd };
            const resolveProcess = spawn(execName, args, options);
            resolveProcess.on('exit', (exitCode) => {
                resolve(exitCode);
            });
            resolveProcess.on('error', (err) => {
                reject(err);
            });
        });
    },
};

export function findCoursierOnPath(cwd: string, execForCode: ExecForCode = defaultImpl): Promise<Array<string>> {
    function availableOnPath(execName: string): Promise<boolean> {
        return execForCode
            .run(execName, ['--help'], cwd)
            .then((ec) => ec === 0)
            .catch(() => false);
    }

    const possibleCoursierNames = ['cs', 'coursier'];
    return possibleCoursierNames.reduce((accP, current) => {
        return accP.then((acc) => {
            return availableOnPath(current).then((succeeeded) => {
                return succeeeded ? [...acc, current] : acc;
            });
        });
    }, Promise.resolve([]));
}