Add support for custom tags at run time

[dhpollack]

It would be nice one could add custom tags via a flow/step decorator or environmental variables. Currently the tagging system seems optimized for post-run tagging, but often times one wants to tag a specific run in order to find that run later. I would propose either a decorator on the flow or environmental variables.

# within flow decorator or on a step
@project(name="my_project", tags=("tag1", "tag2:tag2value" , "tag3"))
class MyFlow(FlowSpec):
  @tags(("start_tag1", "start_tag2:start_tag2_value"))
  def start(self):
    ...

# with an env var
export METAFLOW_USER_TAGS="tag1|tag2:tag2value|tag3"
export METAFLOW_USER_TAGS_DELIMITER="|"

[savingoyal]

you can already do this - METAFLOW_RUN_TAGS='mytag another_tag' python helloflow.py run to attach mytag and another_tag to the execution. This is semantically equivalent to python helloflow.py run --tag mytag --tag another_tag. Would this help?

[dhpollack]

The METAFLOW_RUN_TAGS is exactly what I was looking for. This seems like an undocumented feature. My only complaint now is that it should be in the docs. 😄 Thanks for pointing this out!

[dhpollack]

I'll close this for now.