Allowing empty strings by default for string types

[maldimirov]

The regularString method makes, by default, an empty string a valid value for almost all string formats. This is a bug, since an empty string is not a valid value for e.g. an ipv4 string (which by the JSON Schema spec should be in "dotted quad" format as per RFC 2673).

Seems like the original reasoning behind this is that by default joi marks an empty string as an invalid value for any string type schema. But as I pointed out this breaks the logic for most string formats.

[tlivings]

Yeah I think there was a bug around the way joi handled this.

[maldimirov]

It isn't an issue with joi itself. It's this line in the resolver code. Some string formats don't return in the switch, but break and go to the regularString function, which sets '' as a valid value.

[yosheeck]

This is not fixed yet. Empty string still passes regex validation.
So empty string of '' passes validation against regex of /theText/ which shouldn't be the case I think ?
I proposed a PR to fix it...

[svrnwnsch]

Hey, how is it possible to get the old behavior back which also allows empty strings?

[svrnwnsch]

Ah I see setting minLength: 0 in the json schema works.

[iudex-]

Although @svrnwnsch is correct that setting minLength: 0 fixes the issue, not accepting empty string for the string type directly contradicts the JSON schema specification (as well as the openapi spec).

I can see the point of not accepting empty strings if a format (optional part of the JSON schema spec) is set, but could the behavior of v6.0.0 of accepting empty string be restored for strings without formats?