cue export --output=list for ldjson format

[mikelnrd]

Hi.

I'm experimenting with using cue to import and export ldjson formatted data (basically a list of json structs that are each placed on a single line, separated by a new line character).

I'm able to import this format successfully using the --list option:

cue import --list file.json (after renaming my file.ldjson to file.json)

The feature request: as --list is available as an import option, could something similar be supported as an export option as well?

eg:
cue export --out=list . (or something similar, like --out=ldjson perhaps)

Additionally, perhaps support could be added for the .ldjson extension:
cue import file.ldjson

Loving cue so far. Thanks for your time!

[mpvl]

So IIUC, --list takes a stream and interprets it as a single list value. So the idea is that if the output of CUE is a list, the --list flag, so some list label would cause a list to be exported as a JSON stream. I think it would be best in that case to generate an error if the generated value is not a list.

We could indeed also go off the file name. This is a bit trickier. The CUE tool allows streaming semantics without interpreting it as a list (e.g. for vet). So it may be strange to interpret .ldjson or .jsonl files as lists by default. Conversely, one should then also not assume list semantics when outputing by default, I think. Actually, I think the file.ldjson is already supported, but one would need to use --list.

[mpvl]

FYI, if the list tag were to be supported in the current command line syntax, one could indeed write -o list+stream:foo.json to override writing multiple values to a JSON file (invalid JSON), or write -o list:foo.yaml or -o list:foo.jsonl. Maybe list should be the default for jsonl files, but that would mean that the output will be expected to be a list and not a stream. That said, the mechanism already allows different defaults for different operational modes, so it is not out of the question. But it should become too magical.

[mpvl]

I believe this will be addressed by the CLs that will be submitted soon.

[cueckoo]

This issue has been migrated to cue-lang/cue#280.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.