Firestore: __add__ function for FieldPaths

[chemelnucfin]

No description provided.

[tseaver]

I'm not sure of the utility here. Can @jba or @schmidt-sebastian comment on how / when concatenating FieldPath instances would be used?

[chemelnucfin]

@tseaver For something like this

It's just for convenience, not necessity.

[schmidt-sebastian]

I don't have any concerns if this internal only. Note that this is called append in the Node/Java clients.

[jba]

I have no objections to overloading + to mean append. But in Go I decided to make FieldPaths immutable, because I thought the extra cost was worth avoiding aliasing bugs.

[schmidt-sebastian]

I have no objections to overloading + to mean append. But in Go I decided to make FieldPaths immutable, because I thought the extra cost was worth avoiding aliasing bugs.

The Node and Java implementations return new copies, so maybe that's the route we should go down everywhere?

[jba]

LGTM.