Provide access to tracing-subscriber::fmt::spans or similar API.

[klotzambein]

Feature Request

Crates

tracing-subscriber (version 0.1.3)

Motivation

I would like to add a different logging backend which requires JSON output. Currently, there is no way to do this without reimplementing all of the span tracking done by fmt::Formatter. Most of this logic is in fmt::spans, however, this module is private.

Proposal

Make fmt::spans public or provide some other API.

Workaround

For now, I will just copy the fmt::spans into my project.

PR

I could work on a PR to implement this.

[davidbarsky]

The underlying use-case will be solved using #377, and with the merging of #241, you can be unblocked in writing your own subscriber.