Problem:

#set two properties for UUID 4294967296

$ jack_property -s 4294967296 "a" 1
$ jack_property -s 4294967296 b "2"

#-l lists them

$ jack_property -l
4294967296
key: b value: 2
key: a value: 1

#-l for UUID doesn't list them  <<<<<<

$ jack_property -l 4294967296
$ jack_property -l 4294967296 a
Value not found for a of 4294967296
$ jack_property -l 4294967296 b
Value not found for b of 4294967296

#it seems that 3 chars is the minimum length for value when querying for UUID

$ jack_property -s 4294967296 a 123
$ jack_property -l 4294967296
key: a value: 123
$ jack_property -l 4294967296 a
123

In example-clients/property.c:

/* list all properties for a given UUID */

                        if ((cnt = jack_get_properties (uuid, &description)) < 0) {
                                fprintf (stderr, "could not retrieve properties for %s\n", subject);
                                exit (1);
                        }

cnt is always 0 for values < 3 chars. Why?

In common/JackMetadata.cpp:

int JackMetadata::GetProperty(jack_uuid_t subject, const char* key, char** value, char** type)
int JackMetadata::GetProperties(jack_uuid_t subject, jack_description_t* desc)

This loop gets results:
while ((ret = cursor->get (cursor, &key, &data, DB_NEXT)) == 0) {

but are dropped because of this check:

/* result must have at least 2 chars plus 2 nulls to be valid
if (data.size < 4) {

This rule isn't understood. Explanations are welcome!
Reducing the check to 2 (1 char + null) will consider single char values.
This makes listing properties for a given UUID the same keys as when listing all UUIDs and keys.
No side-effects of lowering the value has been detected (yet).

Note: there is no problem getting "short" values in this method:
int JackMetadata::GetAllProperties(jack_description_t** descriptions)
(as used by jack_property -l without UUID)

jack_property output after change to (data.size < 2):

$ jack_property -s 4294967296 "a" 1
$ jack_property -s 4294967296 b "2"
$ jack_property -l
4294967296
key: b value: 2
key: a value: 1
$ jack_property -l 4294967296
key: b value: 2
key: a value: 1
$ jack_property -l 4294967296 a
1
$ jack_property -l 4294967296 b
2

Note: This change should be considered also for JACK1 (libjack/metadata.c)
to keep implementations in sync.

* [metadata] Metadata properties implementation.

* [metadata] Fixed for shared server metadata-base accessor; alsofixed coding/naming style.

* [metadata] Fixed a tab for space.

* [metadata] Use of Berkeley DB is now truly optional on configure time.

* [metadata] Fixed tabs for spaces, again.

* [metadata] Fixed for shared metadata-base initialization and external clients.

* [metadata] Blind-fix for windows codebase.

* [metadata] Metadata API moved into client-side library only.

* [metadata] Fixed jack_port_uuid() stubbiness, now returning a proper UUID from port index.

* [metadata] Uniform method names.

* [metadata] Fixed PropertyChangeNotify through server async call.