map(select(...)) does not remove entries

[kszafran]

I found a case where jackson-jq returns a different result from jq:

With jq (jq-1.6):

$ jq -cn '{key1: true, key2: false} | map_values(select(.))'
{"key1":true}

With jackson-jq (0.0.10) I get:

{"key1":true,"key2":null}

So key2 is not removed. Perhaps it has something to do with the |= operator, but the footnote in the readme mentions only throwing errors.

[eiiches]

Thank you for reporting! I've confirmed the issue.

$ jq-1.6 -cn '{key1: true, key2: false} | map_values(select(.))'
{"key1":true}
$ jq-1.5 -cn '{key1: true, key2: false} | map_values(select(.))'
null
$ java -jar jackson-jq-cli-0.0.10.jar -cn '{key1: true, key2: false} | map_values(select(.))'
{"key1":true,"key2":null}
$ java -jar jackson-jq-cli-1.0.0-preview.20190925.jar --jq 1.5 -cn '{key1: true, key2: false} | map_values(select(.))'
jq: error: `|= empty` is undefined. See https://github.com/stedolan/jq/issues/897
$ java -jar jackson-jq-cli-1.0.0-preview.20190925.jar --jq 1.6 -cn '{key1: true, key2: false} | map_values(select(.))'
jq: error: `|= empty` is undefined. See https://github.com/stedolan/jq/issues/897

As you've guessed, this is because map_values/1 is defined as def map_values(f): .[] |= f, where ... |= f is undefined when f is empty. I'm not yet sure what to do with this behavior...