Propagate tags to child spans

[LumaC0]

Description

A logfire.span argument that allows child spans and records to inherit tags. All child spans (a relationship that looks to be defined by index in OPEN_SPANS) would inherit tags from surrounding spans that have propagate_tags=True. Spans that set the argument to False (the default) do not pass tags to child spans.

Proposal

logfire.config()

with logfire.span("first span", _tags=["one"], _propagate_tags=True): # has tag ["one"]
    logfire.info("first") # has tag ["one"]

    with logfire.span("second span", _tags=["two"]): # has tags ["one", "two"]
        logfire.info("second", _tags=["t1"]) # has tag ["one", "t1"]

        with logfire.span("third span", _tags=["three"], _propagate_tags=True) # has tags ["one", "three"]
            logfire.info("third") # has tags ["one", "three"]

[alexmojaki]

Try logfire.with_tags

[LumaC0]

@alexmojaki I don't think that will work across files. logfire.with_tags creates a new instance of logfire. if I create that new instance in file1.py and, within that file, create a span that encapsulates ClassInFile2().create() which exists in file2.py, I can't import the logfire instance from file1.py because of circular import issues.

Sorry if this is unclear or I am missing something

[alexmojaki]

Can't you define the instance in another file that both file1 and file2 import?

[LumaC0]

I could hack this together in each of my projects.

(I would instantiate a Logfire instance (not using with_tags) in file3 and just keep updating its internal _tags attribute)

this is fine but it's not really a long term solution.

[alexmojaki]

OK, I guess you're using tags in a way that's more dynamic than what with_tags was intended for.

I would recommend creating a context variable and passing the value to _tags rather than modifying a global shared logfire instance. But I understand that this is still inconvenient. We should create an API that automates this, without requiring opening a span, and that also propagates things like attributes and levels.