A logger layout that renders through logtree

Bridges the logger package (https://daroczig.github.io/logger/) into logtree's tree rendering. logger's own per-call pipeline is formatter() -> layout() -> appender(): only the layout stage receives the structured level object (an integer with a "level" attribute such as "INFO") – appender() only ever sees a pre-formatted character line – so a custom layout, not a custom appender, is the correct integration point. Register it as logger's layout and pair it with logger::appender_void (a ready-made no-op) so that logtree's rendering, which happens as a side effect of the layout call, is the only visible output:

Usage

layout_logtree(
  level,
  msg,
  namespace = NA_character_,
  .logcall = sys.call(),
  .topcall = sys.call(-1),
  .topenv = parent.frame(),
  .timestamp = Sys.time()
)

Arguments

level

A logger log level object (e.g. logger::INFO), as passed in by logger's internal dispatch.

msg

Character scalar, already formatted by logger's formatter stage (glue interpolation has already happened by this point).

namespace, .logcall, .timestamp

Unused; accepted only because logger's dispatcher calls every layout with this exact signature (see logger::layout_simple).

.topcall

The call logger was invoked from, supplied by its dispatcher. Used as the leaf's call site for the trace column.

.topenv

Unused; part of logger's layout signature.

Value

character(0), invisibly. The record is discarded by logger::appender_void() regardless, so its content is irrelevant; a zero-length character vector matches logger's layout contract.

Details

logger::log_layout(logtree::layout_logtree)
logger::log_appender(logger::appender_void)

logger severities map onto logtree leaf levels as: FATAL/ERROR -> log_error(), WARN -> log_warn(), SUCCESS -> log_success(), INFO -> log_info(), DEBUG/TRACE -> log_debug() (logger has two debug-ish tiers, logtree has one, so both collapse to the same leaf). Note logger's own log_threshold() already gates before the layout is ever invoked; logtree_threshold() is then an independent, second gate applied on top of that – both legitimately apply at once, this is not a bug.

When the trace theme slot is on, the leaf's call site is taken from logger's own .topcall rather than from logtree's usual frame walk. That matters: this layout is what calls the leaf, so a frame walk would report layout_logtree as the origin of every routed line instead of the logger::log_info() call in your code.

Examples

if (rlang::is_installed("logger", version = "0.3.0")) {
  logtree_reset()
  logger::log_layout(layout_logtree, namespace = "logtree_demo")
  logger::log_appender(logger::appender_void, namespace = "logtree_demo")
  log_step("Demo step")
  logger::log_info("hello", namespace = "logtree_demo")
}
#> ▶ Demo step
#> ├─ ℹ hello
#> └─ ◌ Done  0.01s