Why can't I use the membership operator together with the pipe operator?

[stephanos]

One of the examples on the playground is

tweets | filter(.Content contains "Hello") | map(.User) | first()

which is very sleek and elegant. However, what would be even more convenient is

tweets | find(.Content contains "Hello") | .User

Is there anything I'm missing to make this work?

There's

tweets | find(.Content contains "Hello") | get("User")

but now you're losing type-safety, I suppose.

[antonmedv]

In Expr, pipes designed to always work with function. Expr parser checks if there is a function call after a pipe. This approach simplifies a lot of things and makes syntax consistent.

One way to solve it is to use variables.

let user = tweets | find(.Content contains "Hello"); 
user.User

The get built-in keep it's type information. It's a special built-in and have a special handling in type check.

[stephanos]

Thank you for the swift response! That's a reasonable workaround 👍

For what it's worth, I don't know if it's worth considering, but maybe - given the constraint you outlined - a new function like get that takes a membership expression instead of a string would be nice. Like:

tweets | find(.Content contains "Hello") | get(.User)

Just throwing it out there :)

[antonmedv]

Nice idea actually. Only a few coronal cases which need to be understood.

get(.User.Name)
get(.Func())
get(.Math + 42)
get(42)

[stephanos]

I'd disallow anything that isn't a membership operation (ie the first line), to be honest.