BitLogger/docs/api/library-logger-warn.md

name, group, category, update-time, description, key-word

name	group	category	update-time	description	key-word
library-logger-warn	api	facade	20260613	Emit a warn-level record through a LibraryLogger facade by delegating to the wrapped logger's warn shortcut.	library facade warn public

Library-logger-warn

Emit a warn-level record through the library-facing sync logger. This is the convenience wrapper for log(Level::Warn, ...) on LibraryLogger[S].

Interface

pub fn[S : Sink] LibraryLogger::warn(
  self : LibraryLogger[S],
  message : String,
  fields~ : Array[Field] = [],
) -> Unit {

input

• self : LibraryLogger[S] - Library-facing logger that should emit the warning record.
• message : String - Warning message text.
• fields : Array[Field] - Optional structured fields attached to the record.

output

• Unit - No return value. The record is handled according to the current threshold and wrapped sink pipeline.

Explanation

Detailed rules explaining key parameters and behaviors

• This helper delegates to warn(...) on the wrapped logger, which in turn uses log(Level::Warn, ...).
• Warning records are useful for abnormal but non-fatal conditions.
• Per-call target override is not exposed here; use log(...) when that is required.
• All sink-side wrappers still participate normally in the write path.
• Broader composition helpers remain on the underlying Logger[S] and require to_logger() first.

How to Use

Here are some specific examples provided.

When Signal A Recoverable Library Problem

When an operation degraded but still continued:

logger.warn("cache miss ratio increased")

In this example, the event is elevated above normal information without being treated as a hard failure.

When Attach Structured Warning Context

When a warning should include machine-readable detail:

logger.warn("retry scheduled", fields=[field("attempt", "3")])

In this example, the warning remains easy to filter and inspect later.

And any shared context already carried by the facade still participates through the wrapped logger pipeline.

Error Case

e.g.:

• If the logger minimum level is above Warn, the call returns without writing a record.

• If a target override is needed at this call site, use log(...) instead of this shortcut.

• If callers need broader composition helpers after logging, they must unwrap first with to_logger().

Notes

1. Use this helper for degraded or suspicious states that do not stop execution.

2. Warning logs are often a practical signal threshold for alerting or separate routing.

3. Use log(...) instead when the call site needs a per-call target override or a dynamic level.