Library-async-logger-warn

Enqueue a warning-level record through the library-facing async logger. This is the convenience wrapper for log(Level::Warn, ...) on LibraryAsyncLogger[S].

Interface

pub async fn[S] LibraryAsyncLogger::warn(
  self : LibraryAsyncLogger[S],
  message : String,
  fields~ : Array[@bitlogger.Field] = [],
) -> Unit {

input

• self : LibraryAsyncLogger[S] - Library-facing async logger that should receive the warning record.
• message : String - Warning message text.
• fields : Array[@bitlogger.Field] - Optional structured fields added to the record.

output

• Unit - No return value. The record is handled according to logger state and policy.

Explanation

Detailed rules explaining key parameters and behaviors

• This helper delegates to warn(...) on the wrapped async logger, which in turn uses log(Level::Warn, ...).
• The record is still subject to min-level gating, stored shared context fields, patching, filtering, and overflow policy.
• This helper does not accept a per-call target override. It uses the facade's stored target unless the facade was derived earlier with with_target(...) or child(...).
• Warning records are useful for degraded but non-fatal runtime conditions.
• Use this helper when a named warning call is clearer than a raw log(...) call.
• Async state helpers remain on the underlying AsyncLogger[S] and require to_async_logger() first.

How to Use

Here are some specific examples provided.

When Need Async Degradation Signals In Library Code

When the system should report a non-fatal problem:

logger.warn("retry budget running low")

In this example, the event is surfaced at warning severity without using the generic log(...) form.

When Attach Structured Warning Detail

When a warning event should include context:

logger.warn(
  "queue near capacity",
  fields=[@bitlogger.field("pending", "64")],
)

In this example, the warning carries structured operational detail.

And any shared context fields already stored on the facade are still prepended before these per-call fields.

And the write still uses the facade's stored target because this shortcut does not take a one-off target= override.

Error Case

e.g.:

• If the logger minimum level is above Warn, the record is skipped before enqueue.

• If the logger is closed or overflow policy prevents acceptance, the write may not become a normal queued record.

• If callers need a per-call target override, they should use log(...) instead of this fixed-level shortcut.

Notes

1. Use this helper for notable but non-fatal async runtime conditions.

2. Pair warnings with structured fields when operators need quick context.

3. Use to_async_logger() first when later code needs queue or failure inspection rather than another write shortcut.