fix(ls/search) --json arg error also sent to stdout

[RammasEchor]

What

Added output to STDOUT via npm.output() when:

• npm search --json: outputs an error to STDOUT in json format.
• npm ls --json & a dependency can't be resolved: the json output to STDOUT has an error embedded.

Why

Preserve backwards compatibility for scripts done for 6.x that rely on an error in STDOUT.

References

Fixes #2740

[ljharb]

Why would that be something desirable? Errors should never be printed on stdout, and scripts expecting it need correcting.

[wraithgar]

We don't have this pattern set up in any of our commands, to my knowledge. If we wanted --json mode to start sending errors to stdout, and in json, that would require some discussion at the very least through our rfc process

Leaving this open for now as a reference for a future discussion.

[ljharb]

@wraithgar if errors appear on stdout with --json that's always a bug - anyone setting --json is likely piping it to a json parser, which won't understand anything that's not in JSON itself.

[nlf]

i think i agree with @ljharb on this one, the behavior in npm 6 was that we hang errors off of the json object and print it as part of the json. npm 7 logging errors in non-json to any stream while printing json feels like a bug (and a regression).

[wraithgar]

As discussed at today's open rfc meeting If we were to implement something like this, it would need to be designed from the ground up as a well-defined way to handle errors in --json mode, and then to make the cli conform to that spec.

If you have a solid idea for how npm should be handling errors (both expected and unexpected) please describe it in an rfc.

[RammasEchor]

Thank you everyone for taking the time to review it, and thanks for letting me know why it was not accepted. Maybe next time!