Bloblang `with` method is not properly filtering arrays

[joreetz-otto]

The with method in bloblang is not working as expected (at least for me after reading the doc on field paths) on objects in arrays.

rpk version v24.1.9 (rev 871368edb0)

Example:

root = {"a": [{"b": 1, "c": 2}, {"b": 3, "c": 4}]}
root = root.with("a.*.b")

Expected result:

{"a":[{"b":1},{"b":3}]}

Result

{"a":[{"b":1,"c":2},{"b":3,"c":4}]}

Even these give the same result

root = {"a": [{"b": 1, "c": 2}, {"b": 3, "c": 4}]}
root = root.with("a.1.b")

root = {"a": [{"b": 1, "c": 2}, {"b": 3, "c": 4}]}
root = root.with("a.*.IDONOTEXIST")

[mihaitodor]

Hey @joreetz-otto 👋 Nice catch, I can reproduce that, but not sure if there's an easy way to get it to work with arrays...

As a workaround, you can do this:

root = this
root.a = this.a.map_each(o -> o.with("b"))

Also, if you have multiple levels of nested arrays, it should be possible to use a recursive mapping to apply this workaround.

[joreetz-otto]

Hey @mihaitodor thanks for confirming this so fast.
I will try your workaround.
Can you tell me where the method is implemented? I couldn't find it. I will see if I can manage to fix this.

[mihaitodor]

You'll probably have to dig into gabs: https://github.com/Jeffail/gabs. The method is implemented here. There's also without() here. They're not implemented in the same place since there's some leftover internal cleanup which should get done eventually...

PS: I just looked at the get() method and that handles arrays just fine. I think it's a bit more tricky in the case of with() / without() because * creates a "view" of the object, so I'm not sure what may need to change.