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Delighted to see work continue on jq, which I use for altogether way too many things. I ask this as a fan of both the project and the new pick() feature: are t

Delighted to see work continue on jq, which I use for altogether way too many things. I ask this as a fan of both the project and the new pick() feature: are there any other functions in jq whose interpretation of their arguments is "non-regular" in the sense the PR author means [here][1]? More concretely, the expression `.a, .b.c, .x` means something very different outside a pick call. It represents a uncollected stream of more than one value, rather than a reduction of an object into a subset of itself. The syntax inside a pick call is (I believe) impossible to implement in jq; it has to be a builtin. There's no way to get "regular jq" to extract the path expressions as strings with which to set an object's keys. Ultimately I do think like the addition, but I recognize the tradeoff of "pure" consistency for syntactical brevity. I'd be curious to hear from the maintainers A) whether I'm off-base about the pathexp syntax limitation and B) if there's some philosophy or design principle guiding why and when they might decide to add specialized interpretations of pathexps. [1]: https://github.com/jqlang/jq/pull/2656#issuecomment-1622822023 https://github.com/jqlang/jq/pull/2656#issuecomment-16228220...

wwader 3y ago
Hey, pick is implemented in jq here https://github.com/jqlang/jq/blob/master/src/builtin.jq#L258-L262 https://github.com/jqlang/jq/blob/master/src/builtin.jq#L258... using various path functions. When the jq manual say "path expression" like the argument to pick you can think of it as just normal jq expression but instead outputting values when path/1 is used it will instead output the paths to those values. The limitation is that you only can index into the input (actually including the null value) and don't construct new literals etc. btw an alternative to pick that might be handy at times is the destruction and shorter object construction syntax: # use {a:{b:1},c:2} as input # . as {a:{$b}} will bind $b to 1 # {$b} is shorthand for {b:$b} # {a} is shorthand for {a:.a} $ jq -n '{a:{b:1},c:2} | (. as {a:{$b}} | {$b}), {a}' { "b": 1 } { "a": { "b": 1 } }

wwader 3y ago

Hey, pick is implemented in jq here https://github.com/jqlang/jq/blob/master/src/builtin.jq#L258-L262 https://github.com/jqlang/jq/blob/master/src/builtin.jq#L258... using various path functions. When the jq manual say "path expression" like the argument to pick you can think of it as just normal jq expression but instead outputting values when path/1 is used it will instead output the paths to those values. The limitation is that you only can index into the input (actually including the null value) and don't construct new literals etc. btw an alternative to pick that might be handy at times is the destruction and shorter object construction syntax: # use {a:{b:1},c:2} as input # . as {a:{$b}} will bind $b to 1 # {$b} is shorthand for {b:$b} # {a} is shorthand for {a:.a} $ jq -n '{a:{b:1},c:2} | (. as {a:{$b}} | {$b}), {a}' { "b": 1 } { "a": { "b": 1 } }