--argfile behavior

[pkoppstein]

The manual says:

--argfile name filename:

This option passes the first value from the named file as a value to the jq program

This however is inconsistent with the current behavior, which is (in a sense) itself inconsistent. If file a contains a string, then jq -n --argfile a a '$a' prints it out; but if it contains two strings, or is empty, the same program prints an array.

The current behavior is certainly justifiable, but maybe this is a good time to orthogonalize things a bit -- perhaps even to the point of giving the user the same control over each "argfile" as is afforded with respect to stdin. For example, we could have --argfile, --argfile-slurp, argfile-raw, ...

Food for thought? (No slurping, please.)

[nicowilliams]

Yes, it does this: slurp the file, and if the thing is an array of just one element, it uses that, else it uses the slurped array. That's lame, I agree (yes, I wrote that code :). I'll make it just slurp.

[nicowilliams]

@pkoppstein

$foo can't be bound to a stream. It has to be a value. So either --argfile slurps, or it only gives you the first value found (what if none are found? there would be no way to distinguish an empty file from a file that contains whatever value, probably null, we decide to use to denote "empty file").

I wouldn't be against --slurpfile, but I think having --argfile slurp is good enough.

[nicowilliams]

Hmmm, this is a backwards-incompatible change. --argfile shipped as it was in 1.4.

[nicowilliams]

I may have to revert this change.

[pkoppstein]

@nicowilliams wrote:

Hmmm

(1) The current behavior is inconsistent with the manual, so there is quite a lot of wriggle room here. Since p ^ ~p => q is true for all WFFs p and q. The important thing is that q be well-formed.

(2) The current specification of --argfile (if the manual can be read as a specification) has the advantage that it complements --slurpfile. The more orthogonality, the better.

(3) Please do not read (2) as a strong endorsement of the documented behavior: see (1).

(4) Having control on a file-by-file basis would be a Very Good Thing.

[nicowilliams]

The way to distinguish what happened (slurped vs. not slurped) could be to add a second variable named after the given one.

[nicowilliams]

I'll probably do that and revert the change I pushed earlier.

[nicowilliams]

I think I'll restore the original behavior and add a new argument with better behavior.