Allow configuring JSON encoder for `job.get_meta()` serialization in `web.py`

[Flix6x]

Problem

Viewing the job page leads to a server error if the job.meta contains objects that are not serializable by the default JSONEncoder.

Currently, rq-dashboard serializes job metadata like this (in web.py):

json.dumps(job.get_meta())

This uses the default JSON encoder. In some cases, job metadata may contain types that aren’t JSON-serializable by default (e.g., datetime.datetime, datetime.timedelta, and corresponding Pandas classes). This causes serialization errors when viewing job details in the dashboard.

Proposal

It would be helpful if rq-dashboard allowed users to configure or pass a custom json.JSONEncoder (or a callable) for this serialization step. For example:

• Add a configuration option (e.g., RQ_DASHBOARD_JSON_ENCODER) that points to a JSONEncoder subclass or function.
• Or, allow passing an encoder when initializing the dashboard app.

For example:

from datetime import datetime

class CustomEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, datetime):
            return obj.isoformat()
        return super().default(obj)

# somewhere in config
RQ_DASHBOARD_JSON_ENCODER = CustomEncoder

And the desired change in web.py:

json.dumps(job.get_meta(), cls=current_app.config.get("RQ_DASHBOARD_JSON_ENCODER", json.JSONEncoder))

Would you be open to a PR adding this configurability?

[cjlapao]

@Flix6x sure, create the pr so we can have a look