External objects should not be modified

[micnic]

Hey, I was playing around with Object.seal() and Object.freeze() and discovered that internally Node is trying to modify my objects and I got the following in fs.watch:

TypeError: Can't add property recursive, object is not extensible

In my opinion external objects should not be modified by Node, as I observed sometimes this rule is respected, sometimes - only partially (in case of fs.appendFile).

Do we have anywhere this rule specified?

cc @nodejs/collaborators

[targos]

I don't know of any written rule but I agree that we should not modify user-supplied objects.

[thefourtheye]

We can solve this problem for options in #7165 by making a copy.

[targos]

We can solve this problem for options in #7165 by making a copy.

Another way is to do options = Object.create(options);

[micnic]

@thefourtheye yes, it would be a good place to add a solution for the fs module, I could not find yet this issue for other core modules.

util._extend() should be used in this case I guess

[thefourtheye]

@micnic I used Object.assign and introduced a commit in #7165.

[micnic]

@thefourtheye as I know from #7208 and #7255 Object.assign() performs slower than util._extend() and it was decided to use it until Object.assign() will have a better performance

[thefourtheye]

@micnic Right. I use util._extend now.

[thefourtheye]

Fixed in 7542bdd