Escape control characters

[lilydjwg]

Feature Request

Crates

• tracing-subscriber

Motivation

Sometimes the string being logged contains control characters (bytes 0..=31). tracing currently outputs them literally, causing:

• some characters are not visible
• bell rings (one way or the other)
• systemd-journald thinks them binary and breaks one log line into multiple records that aren't easy to read

Proposal

When the non-JSON formatter is used, escape control characters inside user-provided event strings.

Alternatives

Let the caller do the escaping. There may be a lot different places to fix across different projects.

See also hickory-dns/hickory-dns#2895.