蓝鸟的承诺catch（）不使用Promise.CancellationError调用内部函数

Question

When a file is missing, I am trying to cancel the promise. However, when I do this I see in the output:

Unhandled rejection Error: ENOENT, open '/home/one/github/infrastructure_manager_ui/gulp/util/token-file.json'
  at Error (native)

and also createTokenFile() does not run as it should. Not sure what I am doing wrong:

 function refreshToken() {
        var tokenFile = path.join(__dirname, 'token-file.json');
        return tokenPromise = fs.readFileAsync(tokenFile, {encoding: 'utf-8'})
        .then(JSON.parse)
        .cancellable()
        .catch(Promise.CancellationError, function(err) {
            console.log(err);
            if (err.code !== 'ENOENT') { 
                throw err;
            } else {
                createTokenFile();
                tokenPromise.cancel();
            }
        });
}

Answer 1

.cancellable() is not doing anything here. .cancellable() turns a promise into one can be manually cancelled. You're not doing anything to cancel it here, so it's not being cancelled.

If you want to catch the file read error, you should just catch it:

function refreshToken() {
        var tokenFile = path.join(__dirname, 'token-file.json');
        return tokenPromise = fs.readFileAsync(tokenFile, {encoding: 'utf-8'})
        .then(JSON.parse)
        .catch(function(err) {
            console.log(err);
            if (err.code !== 'ENOENT') { 
                throw err;
            } else {
                return createTokenFile();
            }
        });
}