filter Filter will convert null and undefined to strings

[rince1013]

filterFilter will convert null and undefined to strings and use that to filter
This makes the default comparator unusable with arrays that have fields with null or undefined values.
This seems to be a regression - it works as expected in <=1.3.5

Here is plnkr
http://plnkr.co/edit/P67JlZv83ea8J5ZFw9Ce?p=preview

[Narretz]

I don't see it, maybe I don't understand the problem.
If you have search.name = null, it will filter correctly. If you have search.name = undefined, it will not match something with name: undefined , neither <= 1.3.5 nor after.

[pkozlowski-opensource]

This sounds somehow similar to #11312 - different filter but the same root cause.

[rince1013]

Maybe this update plunker will make it a bit clearer
http://plnkr.co/edit/f7trY8?p=preview

I have two values in the array where name is not a string - one is null and one is undefined

[{name:null, phone:'The value of name is null'},
{name:undefined, phone:'The value of name is undefined'},
{name:'Mike', phone:'555-4321'},
{name:'Adam', phone:'555-5678'},
{name:'Julie', phone:'555-8765'},
{name:'Juliette', phone:'555-5678'}]

If I search this array for names with 'u', you would expect only Julie and Juliette to return. But, also the null and undefined results are returned. The filter filter is treating null and undefined as strings, and then using the converted string value to determine if the array matches the search.

If I change the Angular version to 1.3.5, the filter filter works as expected

[rince1013]

And here is the offending line
https://github.com/angular/angular.js/blob/master/src/ng/filter/filter.js#L180
in function createPredicateFn

actual = lowercase('' + actual);

This line implicitly converts null into "null" and undefined into "undefined"

[hamfastgamgee]

Agree that it's very similar to my bug, #11312. Sadly, the broken code isn't shared. :)

[pkozlowski-opensource]

Yeh, this is a valid one.

[gkalpak]

I always have a hard time differentiating between bug fixes and breaking changes when it comes to filterFilter. So, if I understand correctly, this is considered a bug/regression.

The desired behaviour is:

1. null item property | any string filter expression -> NO MATCH
2. null item property | null filter expression -> MATCH
3. undefined item property | any string filter expression -> NO MATCH
4. undefined item property | undefined filter expression -> (irrelevant; no filtering anyway)

(Currently, (1) and (3) match if the filter expression is a subtring of "null"/"undefined" respectively.)

Do I miss something ?

[hamfastgamgee]

I think it's probably expected behavior that null/undefined filter
expressions will match everything as they do today. (I don't think that's
directly stated in gkalpak's post.)

[gkalpak]

They don't do that today (nor did they do it pre 1.3.6) and I don't think they (both) should.

An undefined property of the filter expression is indeed ignored, so it will effectively match anything, since there is no filtering going on (this is mentioned in my previous comment and is what happens today).

A null property of the filter expression, should imo only match against a null property. I don't think null should match anything, since it is specific value and there are cases where you want to find nulls. (I also think this has been discussed and agreed upon during/after the v1.3.6 refactoring of filterFilter, but I am not 100% sure.)
Note, that null did not match anything before the v1.3.6 refactoring either.

[hamfastgamgee]

I think I got confused and probably was conflating explicit null in a filter with the empty string. Yes, I agree that what you say here.