Logger-child

Create a child logger by composing the current target with another target segment. This is the standard API for hierarchical target naming such as app.worker or service.http.client.

Interface

pub fn[S] Logger::child(self : Logger[S], target : String) -> Logger[S] {}

input

• self : Logger[S] - Parent logger whose target should be extended.
• target : String - Child target segment or suffix.

output

• Logger[S] - A new logger value whose default target is the composed child path.

Explanation

Detailed rules explaining key parameters and behaviors

• The returned logger is derived from self; the original logger value is not mutated.
• If the parent target is empty, the child target becomes the full target.
• If the child target is empty, the parent target is preserved.
• If both are non-empty, they are joined with ..
• Only the stored target changes. Sink, min level, and timestamp settings are preserved in the returned logger.
• The wider composition surface stays available on the derived logger, so follow-up calls such as with_timestamp() or log writes continue to work with the composed target.

How to Use

Here are some specific examples provided.

When Need Hierarchical Target Naming

When subsystem logs should stay grouped under a shared namespace:

let logger = Logger::new(console_sink(), target="service")
let worker = logger.child("worker")

In this example, worker emits records under service.worker.

And logger still keeps its original stored target, because child(...) returns a derived logger value instead of mutating the parent.

When Build Deeply Scoped Loggers Step By Step

When deeper target composition should remain readable:

let http = Logger::new(console_sink(), target="app")
  .child("http")
  .child("client")

In this example, the final logger target becomes app.http.client.

Error Case

e.g.:

• If target is empty, the returned logger keeps the original parent target.

• If callers need complete replacement rather than composition, with_target(...) should be used instead.

Notes

1. This is the preferred API for hierarchical logger naming.

2. Composition uses . as the separator between parent and child segments.

3. The same compose-and-preserve contract is exercised through the library, configured, and application logger surfaces, not only on the base Logger[S] value.