undefined values are merged about merge-options HOT 4 CLOSED

Fair enough, but the readme clearly states:

merge-options considers plain objects as Option Objects, everything else as Option Values.

As undefined is not a plain object, your examples describe the expected behavior.

Please note: the more recent (non-recursive) spread operator works the same way:

const defaults = { port: 443 };
const options = { port: process.env.PORT };

mergeOptions(defaults, options)
// => { port: undefined }

{...defaults, ...options}
// => { port: undefined }

Hence, in your case, I would suggest to make your environment variables more useful:

// index.js
const mergeOptions = require('merge-options');

const envKeys = [ 'PORT' ];
const env = Object.fromEntries(Object.entries(process.env)
    .filter(([k]) => envKeys.includes(k))
    .map(([k, v]) => [k.toLowerCase(), v])
);

console.log('env:', env)
const options = mergeOptions({ port: 443 }, env);
console.log('options:', options);

$ PORT=8080 node index.js
# env: { port: '8080' }
# options: { port: '8080' }

$ node index.js
# env: {}
# options: { port: 443 }

from merge-options.

Would you accept a PR that added this behaviour as a config option similar to concatArrays called ignoreUndefined or similar?

I run into situations where this would be useful all the time but don't think the world needs Yet Another Options Merging Module.

from merge-options.

👍 @achingbrain I don't see a problem with an option – ignoreUndefined sounds good to me.

from merge-options.

Thanks to @achingbrain (merge-options@^2.0.0):

const mergeOptions = require('merge-options').bind({ignoreUndefined: true});

const result = mergeOptions({port: 443}, {port: process.env.PORT});
console.log(result);

$ PORT=8080 node index.js 
# { port: '8080' }

$ node index.js 
# { port: 443 }

from merge-options.