`range` expression with invalid input produces infinite output instead of error

[derekleverenz]

If i give range an invalid input, it produces a seemingly infinite sequence of numbers as output, until i terminate it (saw this in an embedded usecase too, where it ended up with the process being killed for OOM) eg:

echo '{"a": 1}' | jaq 'range(.)'

produces a sequence starting from 0 and never terminating. Also replicated with an empty object {}, empty array [], and array with data as inputs.

the jq tool produces an error. echo '{"a": 1}' | jq 'range(.)' results in jq: error (at <stdin>:1): Range bounds must be numeric

This is with jaq 2.3.0, compiled from source via cargo install --locked jaq. Rustc version 1.89, ubuntu linux 22.04, x86_64

[01mf02]

Hi @derekleverenz, I'm aware of this behaviour. This comes from the fact that jq has an (IMO) surprising implementation of range($from; $to), which is not the same as range($from; $to; 1) (where 1 is the step size). The latter will accept non-numeric bounds, whereas the former rejects them. In jaq, both are the same, because range/1 and range/2 are both defined via a fast implementation of range/3. On the other hand, jq defines range/1 via a fast implementation of range/2 and defines range/3 completely differently. As a side effect, jaq has a vastly more rapid range/3 than jq, and it accepts non-numeric bounds for all range variants.

You can check that range/3 accepts non-numeric bounds also in jq via:

$ jq -n 'limit(5; range(""; []; "a"))'
""
"a"
"aa"
"aaa"
"aaaa"

That yields the same output for jq and jaq.

[01mf02]

By the way, the range behaviour was previously brought up in #72, but the other way. Previously, jaq complained when range was used on anything that is not an integer. Now, it does not complain at all. ;)

[wader]

For reference there is a jq PR jqlang/jq#3267 to make it more like jaq but not sure why it was never merged

[derekleverenz]

Ah, i see. I guess i would have liked it better the old way, but since its intentional, doesnt seem like a bug. Thanks