Correction: Dagit displays all of the metadata correctly for the materialized asset. 🤷🏻‍♂️

Based on debugging the stack trace from the error below, it looks like PyYAML is having trouble parsing the MetaData objects passed to the RunConfig. I theorize that Dagster may need to create a representer for the Dagster-specific objects for the

dump

function to use:

Operation name: RunRootQuery

Message: ('cannot represent an object', TextMetadataValue(text='12'))

Path: [ "pipelineRunOrError","runConfigYaml" ]

Locations: [ { "line": 14,"column": 3 } ]

Stack Trace:
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\graphql\execution\execute.py", line 521, in execute_field
    result = resolve_fn(source, info, **args)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\dagster_graphql\schema\pipelines\pipeline.py", line 488, in resolve_runConfigYaml
    return dump_run_config_yaml(self._pipeline_run.run_config)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\dagster\_utils\yaml_utils.py", line 150, in dump_run_config_yaml
    return yaml.dump(
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\__init__.py", line 253, in dump
    return dump_all([data], stream, Dumper=Dumper, **kwds)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\__init__.py", line 241, in dump_all
    dumper.represent(data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 27, in represent
    node = self.represent_data(data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:<http://yaml.org|yaml.org>,2002:map', data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:<http://yaml.org|yaml.org>,2002:map', data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:<http://yaml.org|yaml.org>,2002:map', data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:<http://yaml.org|yaml.org>,2002:map', data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 48, in represent_data
    node = self.yaml_representers[data_types[0]](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 207, in represent_dict
    return self.represent_mapping('tag:<http://yaml.org|yaml.org>,2002:map', data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 118, in represent_mapping
    node_value = self.represent_data(item_value)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 58, in represent_data
    node = self.yaml_representers[None](self, data)
  File "C:\Users\<REDACTED>\Miniconda3\envs\<REDACTED>\lib\site-packages\yaml\representer.py", line 231, in represent_undefined
    raise RepresenterError("cannot represent an object", data)

I was able to figure out the issue here and thought I'd share in case anyone else ran into it. In short, I had an asset_sensor where I was grabbing the metadata from the asset materialization event log and using

serialize_value

function to pass it to the op_config for the job triggered by the asset_sensor. The values of the

EventLogEntry.asset_materialization.metadata

are contained in Dagster NamedTuple types such as

TextMetadataValue

and

JsonMetadataValue

. Serializing that metadata object with

serialize_value

resulted in those Dagster-specific types being passed to the downstream job and - because I was trying to deserialize them using

json.loads

- Dagit didn't know how to display those class instances in the job config, resulting in the error and stack trace above. I resolved the issue by replacing the use of

serialize_value

in the sensor to the snippet below:

asset_event_metadata = {
        key: val.value
        for key, val in asset_event.asset_materialization.metadata.items()
    }

I hope this is helpful for others folks in the future. I know our use case of passing metadata from an asset to a downstream job is probably non-standard, so - with my upfront apologies for the direct callout - I'm going to tag @daniel, who has helped me in the past to review this for any unexpected behavior. Please let me know if I can provide any further context or details here.