BitLogger/docs/api/library-logger-with-context-fields.md

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

name	group	category	update-time	description	key-word
library-logger-with-context-fields	api	facade	20260613	Attach reusable structured fields to a LibraryLogger facade.	library facade fields public

Library-logger-with-context-fields

Bind shared structured fields to a LibraryLogger[S]. This is the library-facing API for attaching stable metadata such as component name, plugin id, or request scope without repeating those fields on every log call.

Interface

pub fn[S] LibraryLogger::with_context_fields(
  self : LibraryLogger[S],
  fields : Array[Field],
) -> LibraryLogger[ContextSink[S]] {

input

• self : LibraryLogger[S] - Base facade that should gain shared fields.
• fields : Array[Field] - Structured fields that will be prepended to each emitted record.

output

• LibraryLogger[ContextSink[S]] - New library-facing facade wrapping the original sink with context-field merging behavior.

Explanation

Detailed rules explaining key parameters and behaviors

• This API delegates to the wrapped logger's with_context_fields(...) behavior and then narrows the result back to LibraryLogger.
• Context fields are merged at write time rather than by mutating previously created records.
• The returned facade carries ContextSink[S] because the sink pipeline has been extended.
• bind(...) is an ergonomic alias for this same behavior.

How to Use

Here are some specific examples provided.

When Need Stable Library Metadata On Every Record

When a package should attach fixed metadata to all emitted records:

let logger = default_library_logger()
  .with_target("plugin")
  .with_context_fields([field("plugin", "alpha"), field("region", "cn")])

In this example, both fields are automatically included on every later write.

When Combine Target Scoping And Shared Fields

When a subsystem facade should carry both a target and stable context:

let worker = LibraryLogger::new(console_sink(), target="sdk")
  .child("worker")
  .with_context_fields([field("component", "worker")])

In this example, target composition and field binding stay separate but compose cleanly.

Error Case

e.g.:

• If fields is empty, the returned facade remains valid and simply adds no extra metadata.

• If duplicate field keys are provided, all fields are still emitted for downstream formatting or inspection.

Notes

1. Use this for stable shared metadata, not highly dynamic event-specific values.

2. The narrower LibraryLogger surface is preserved after context binding.