Add `--format` flag to `language core|plugin|theme`

[RoundAboutWEB]

All update commands for language files with "- json" generate an error.

wp language core update --dry-run --json
wp language plugin update --all --dry-run --json
wp language theme update --all --dry-run --json
wp language core update --json
wp language plugin update --all --json
wp language theme update --all --json

[schlessera]

There's two things happening here:
a.) --json is a deprecated flag that was later replaced by the more generic --format=json, as we also support other formats by now. WP-CLI automatically turns --json into --format=json for backward compatibility.
b.) The above three commands don't support a --format flag, so the error just tells you that you're using an unknown flag for these commands.

So the behavior of WP-CLI is correct here, even if it might be slightly misleading due to backward compatibility logic.

As to whether we would want to add --format support to these commands, it would help to know what specific use case you are trying to solve.

[RoundAboutWEB]

json is needed to see if any updates are pending

[RoundAboutWEB]

Is there any hope that this case (reported September 2019) will be handled?

[schlessera]

It is not a current priority.

Are you interested in looking into this for creating a PR? If so, I'm happy to assist you in whatever way I can to get this implemented.