field_filter_spans intermittently fails

[jyn514]

Bug Report

Version

Master branch (currently a8cc977).

Platform

I noticed the failure on MacOS, but it may appear on other platforms.

Crates

tracing and tracing-subscriber.

Description

Occasionally field_filter_spans fails with the following error:

}
[field_filter_spans] enabled -> true
thread 'field_filter_spans' panicked at '[field_filter_spans] more notifications expected: [Enter(MockSpan { metadata: Expect { name: Some("span3"), level: None, target: None } }), Event(MockEvent { fields: Some(Expect { fields: {"something": Any}, only: false }), parent: None, metadata: Expect { name: None, level: Some(Level(Debug)), target: None } }), Exit(MockSpan { metadata: Expect { name: Some("span3"), level: None, target: None } }), Nothing]', tracing-subscriber/tests/../../tracing/tests/support/subscriber.rs:528:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

See also #991 (comment)

[hawkw]

see also #449

[jyn514]

Oops, this is a duplicate then.

[hawkw]

Technically it's not, since #449 is for a different test in the same file :) But, I think the issue is caused by an interaction between the filtering directives for those two tests.