put-metadata does not work as expected since 3.x

[demetz]

We recently upgraded from 2.x to the latest version.

I am no longer able to set metadata for a single property:

url = 'https://xxx/api/2/things/[thingid]/features/myfeature/properties/myproperty/temperature'

metadata = [
    {
        "key":"/unit",
        "value": "°C"
    }
]

r = requests.put(url, headers={"Content-Type":"application/json", "put-metadata":json.dumps(metadata)}, auth=(ditto_user, ditto_pass),json=64.5)

Expected behavior: value is written and metadata is available /features/myfeature/properties/myproperty/temperature/unit

Actual behavior: only value is written

[thjaeckle]

Hi @demetz
Thanks for reporting this issue.

There were some enhancements to metadata in Ditto 3.0, I assume some behavior may have changed.

Could you please try using no trailing slash in the "key", so:

{
        "key":"unit",
        "value": "°C"
    }

I could imagine that this somehow changed if Iook at the docs.

[demetz]

unfortunately, same result: ditto returns a 204 and the actual value is written, however no metadata is created.

specifying a nested key (e.g. /test/unit) for _metadata works as expected.

[thjaeckle]

Could reproduce via sandbox:

curl --location --request PUT 'https://ditto.eclipseprojects.io/api/2/things/org.eclipse.ditto:lamp01/features/LampFeature/properties/powerConsumption' \
--header 'Authorization: Basic ZGl0dG86ZGl0dG8=' \
--header 'put-metadata: [{"key":"unit","value": "Watts"}]' \
--header 'Content-Type: application/json' \
--data '23.23'

Retrieving the metadata:

curl --location --request GET 'https://ditto.eclipseprojects.io/api/2/things/org.eclipse.ditto:lamp01?fields=thingId%2Cfeatures%2C_metadata' \
--header 'Authorization: Basic ZGl0dG86ZGl0dG8='

Did not apply the metadata as expected ("powerConsumption" is an empty object instead of having the "unit" key):

{
    "thingId": "org.eclipse.ditto:lamp01",
    "features": {
        "LampFeature": {
            "properties": {
                "powerConsumption": 23.23
            }
        }
    },
    "_metadata": {
        "features": {
            "LampFeature": {
                "properties": {
                    "powerConsumption": {}
                }
            }
        }
    }
}

As @demetz mentioned, using a nested key works:

curl --location --request PUT 'https://ditto.eclipseprojects.io/api/2/things/org.eclipse.ditto:lamp01/features/LampFeature/properties/powerConsumption' \
--header 'Authorization: Basic ZGl0dG86ZGl0dG8=' \
--header 'put-metadata: [{"key":"test/unit","value": "Watts"}]' \
--header 'Content-Type: application/json' \
--data '23.23'

Result:

{
    "thingId": "org.eclipse.ditto:lamp01",
    "features": {
        "LampFeature": {
            "properties": {
                "powerConsumption": 23.23
            }
        }
    },
    "_metadata": {
        "features": {
            "LampFeature": {
                "properties": {
                    "powerConsumption": {
                        "test": {
                            "unit": "Watts"
                        }
                    }
                }
            }
        }
    }
}

[thjaeckle]

Any help on fixing this bug would be appreciated, I currently don't have the resources to work on a fix.

[thjaeckle]

@demetz will be fixed in upcoming 3.4.0 release