Suggested alternative for deprecated angular.merge doesn't behave exactly like the deprecated method.

[absrd]

I'm submitting a ...

• bug report
• feature request
• other (Please do not submit support requests here (see above))

Current behavior:

It's more a misguided suggestion in documentation. It is with regards to deprecation of angular.merge and the suggested alternative, Lodash.merge. Lodash doesn't handle defined keys with undefined values, i.e. if I have an object a = {b: 1} and merge it with another object Lodash.merge(a, {b: undefined}) then the result is {b: 1}, which would be {b: undefined} in angular.merge.

Expected / new behavior:

The alternative library should be as close to the deprecated method.

Minimal reproduction of the problem with instructions:

Look above.

AngularJS version: 1.x.y

Browser: all

Anything else:

Suggest another library, e.g: https://www.npmjs.com/package/deepmerge
I'm not associated with the above library other than I'm now using that instead of Lodash.

[frederikprijck]

Interesting, looks like it's idd not the same behavior, see: https://plnkr.co/edit/zVoIVIz52ZAUTUsN133T?p=preview

I guess this should be changed:

angular.js/src/Angular.js

Line 426 in 464dde8

* This function is deprecated, but will not be removed in the 1.x lifecycle.

Not sure deepmerge is the best approach as I'm not familiar with it so I can't realy tell.

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Note: even tho Object.assign() is not deep cloning, it's interesting to note _.merge is also different from Object.assign when it comes to first level properties.

[gkalpak]

I don't think we need a function that is 100% compatible with angular.merge(). Maybe we should make it more clear that we recommend using a similar (not identical) general purpose merge function and that lodash.merge is a popular example, not necessarily the "officially recommended" replacement.