Default value of null in an union schema causes panic.

[amrx101]

When we have a union type with null and a default value of null, the serialisation causes error at run time.

The schema. Here in we can see that we have union type with null and default value null.

{
	"namespace": "atherenergy.vcu_cloud_connect",
    "type": "record",
	"name": "common",
	"fields" : [
		{"name": "can_id", "type": ["null", "string"], "default": null},
        {"name": "data", "type": ["null", "string"], "default": null},
        {"name": "value", "type": ["null", "string"], "default": null},
        {"name": "key", "type": ["null", "string"], "default": null},
        {"name": "timestamp", "type": ["null", "double"], "default": null},
        {"name": "start_timestamp", "type": ["null", "string"],"default": null },
        {"name": "end_timestamp", "type": ["null", "string"], "default": null},
        {"name": "release_name", "type": ["null", "string"], "default": null},
        {"name": "bms_version", "type":["null", "string"], "default": null},
        {"name": "charger_version", "type":["null","string"], "default": null},
        {"name": "sim_ccid", "type":["null", "string"], "default": null},
        {"name": "sim_cimi", "type":["null", "string"], "default": null},
        {"name":"mender_artifact_ver", "type":["null", "string"], "default": null},
        {"name":"mcu_version", "type": ["null","string"], "default": null},
        {"name": "vin", "type": ["null","string"], "default": null},
        {"name": "bike_type", "type": ["null","string"], "default": null},
        {"name": "motor_version", "type": ["null","string"], "default": null},
        {"name": "system_boot_time", "type": ["null","string"], "default": null},
        {"name": "mode", "type": ["null","int"], "default": null},
        {"name": "ttff_s", "type": ["null","float"], "default": null},
        {"name": "error_code", "type": ["null","string"],  "default": null},
        {"name": "is_valid", "type": ["null","int"],  "default": null},
        {"name": "ACC_X_MPS2", "type": ["null","float"],  "default": null},
		{"name": "ACC_Y_MPS2", "type": ["null","float"],  "default": null},
		{"name": "ACC_Z_MPS2", "type": ["null","float"],  "default": null},
		{"name": "GYR_X_DEG", "type": ["null","float"],  "default": null},
		{"name": "GYR_Y_DEG", "type": ["null","float"],  "default": null},
        {"name": "GYR_Z_DEG", "type": ["null","float"],  "default": null}
	]
}

let sample_data = r#"{
            "ACC_X_MPS2": "33213.322",
            "ACC_Y_MPS2": "323.909803",
            "ACC_Z_MPS2": "2121.443",
            "GYR_X_DEG": "2323.111",
            "GYR_Y_DEG": "223.11274",
            "GYR_Z_DEG": "3434.2211"
        }"#;
        let sample_imu = serde_json::from_str(imu_data).unwrap();
        println!("{:?}", sample_imu);

        let rec = Rr::from_json(sample_imu, &ss).unwrap();

This serialisation results in Err` value: DefaultValueParse

[creativcoder]

Hi @amrx101

Thanks for reporting this. Looks like we need to put priority on iterating over the schema fields when creating fields of the Record instance. Right now from_json iterates over the fields on the provide json value.

Here's how we might solve this:

iterate over the schema fields,
         if the field is in json - use that field
         else parse value if there's a default value in schema.
else we bail with an error.

Code:

avrow/src/value.rs

Line 93 in e79a420

pub fn from_json(

Note: The schema might also be a union so we need to take into account of trying all the variants in the union schema when parsing default value from schema, as is the case with your example.

Wanna make a PR for this?

[amrx101]

Yup will make a PR for that.

[creativcoder]

@amrx101 Any update on this?

[amrx101]

Not yet. Bit busy here due to the releases coming in