Passing a bogus value to --with-jsondir=XXX does not make any noise

[strk]

Try ./configure --with-jsondir=/tmp

It won't error out. It'll go looking around for your library and if found would tell you json is enabled.

Didn't try not having the library but I suspect it would just tell you json is disabled.

I think it should error out instead, as the user specification must be meaningful.

[strk]

For comparison: ./configure --with-pgconfig=/tmp errors out:

configure: error: the user-specified pg_config file /tmp does not exist

[strk]

Fixed in r9503