Functions that accept and return objects should respect frozenness

For example, with assoc:

var first = Object.freeze({a: 1, b: 2});
var second = R.assoc('c', 3, first);

console.log(Object.isFrozen(second)); // currently false

I believe that Ramda should maintain the frozenness of objects passed in. Discuss!

[kurtmilam]

@matthewp An ESLint rule might help you remain true to your FP principles. It looks like there are multiple options in this area, according to this google search.

That won’t help with libraries that mutate your objects, but it’s a start.

It might be interesting to have a companion library to Ramda that deep-freezes every object returned by any of the library’s functions. I wouldn’t use this in production, and I wouldn’t need it for myself, but it might be useful in a team scenario where not all team members can be trusted to avoid mutation to install the deep-freeze library as a development dependency and have a flag in your app that chooses which version of Ramda to load - deep-freeze for development and vanilla for production.

The excellent partial.lenses library has this behavior baked in. If I understand correctly, it deep freezes all objects returned by its methods if process.env.NODE_ENV is anything other than ‘production’. Everything’s frozen during development, but freezing is turned off in production.

[kurtmilam]

Most Ramda functions that take objects as arguments and return objects work with the objects’ own enumerable properties. There is no isFrozen own enumerable property on any object unless someone has added it explicitly (as you did to first in your example).

Think of R.assoc as being similar to JavaScript’s native Object.assign. This native method, like R.assoc, only takes into account own enumerable properties.

For example, you could naively recreate R.assoc based on Object.assign:

const assocNative =
  ( propName, propVal, target ) =>
    Object.assign( {}, target, { [ propName ]: propVal } )

The object returned by this assocNative function will always be ‘unfrozen’, regardless of whether the target object passed into it was frozen.

See a more thorough example on Ramda’s REPL.

Also, you may be interested in taking a look at Ramda’s Gitter.