Improve alterItems hook: can map to a newly created object

[beeplin]

Previously alterItems only accept a function that use item as a reference, and we have to create/mutate/delete properties. upon the original reference This makes a bunch of lodash tools unusable, since most lodash functions return a new object rather than changing the original input.

This PR allows alterItems accepting a function with a returned value. If the function returns a non-null value, the original item/items are replaced with the returned value; if the function returns nothing, just keep the previous behavior.

Example:

alterItems(item => {
  return _.omit(item, ['a', 'b', 'c'])
}

Please check the code and the tests with caution in case I make some terrible mistakes. ;)

[beeplin]

I realized this is a breaking change, and maybe we should create a new hook for this purpose?

[eddyystop]

Is it really a breaking change? The current version ignores any return value and the docs state "Function modifies item in place."

I would prefer using if (typeof result === 'object' && object !== null).

I might have to delay updating the docs for 1 or 2 weeks as I'm focused on something else.

[beeplin]

Is it really a breaking change?

Say someone has the following code:

alterItems(item => doSomethingForItem())

Before this PR it would work fine, but after the PR the item will be replaced by the returned value of doSomethingForItem, because item => doSomethingForItem() is equal to item => { return doSomethingForItem() }. Note the hidden return.

[eddyystop]

doSomethingForItem would have to return something to have a problem. I could agrue that's bad code; that people get burned when playing with edge cases.

alterItems has not be out very long so the 'install base' is small. Buzzard is not yet released. V4.x.x is not yet published to npm.

I would rather not create YAH (yet another hook).

[beeplin]

Agree. Me too hate YAH :))

So I will take your if (typeof result === 'object' && object !== null) and update the PR.

[beeplin]

done.

[eddyystop]

feathers-plus/docs#10

I'll wait to bump the semver.