Overview

Scriptorium.Parchment is the structured logging layer for the Scriptorium family. It exposes severity-based logging methods, a composable sink system, and child loggers with automatic prefixes.

Installation

dotnet add package Scriptorium.Parchment

Usage

Create a logger with one or more sinks, then call the severity method you need:

open Scriptorium.Parchment
open Scriptorium.Parchment.Sinks

let logger = Parchment.Create(Universal.console ())

logger.info "Server started on port 3000"
logger.warning "Deprecated API called"
logger.error "Connection failed"
logger.infof "Processing %d items" itemCount

// Child loggers prefix every message automatically
let db = logger.Child("db")
db.info "connected" // → [db] connected
db.error "query failed" // → [db] query failed

Six severity levels are available, from highest to lowest priority:

error > warning > info > verbose > debug > silly

Each has a plain and a formatted (f-suffixed) variant.

Filtering

Set logger.Level to suppress messages below a given severity. The default is Info.

logger.Level <- Severity.Warning

logger.error "logged" // ✓ Error ≤ Warning
logger.warning "logged" // ✓ Warning ≤ Warning
logger.info "not logged" // ✗ Info > Warning

Child loggers

logger.Child(prefix) creates a logger that prepends [prefix] to every message:

let db1 = logger.Child("db")
let cache = logger.Child("cache")

db1.info "connected" // → [db] connected
cache.warning "cache miss" // → [cache] cache miss

Children can be nested — prefixes are concatenated in order:

let db2 = logger.Child("db")
let query = db.Child("query")

query.info "SELECT *" // → [db][query] SELECT *
query.error "timeout" // → [db][query] timeout

Custom sinks

A Sink is a Severity -> string -> unit function, so any output target works:

let messages = ResizeArray<string>()

let collectingSink: Sink = fun severity msg -> messages.Add($"[{severity}] {msg}")

let myLogger = Parchment.Create(collectingSink)

Sinks can be added or removed at runtime with logger.Add(sink) and logger.Remove(sink).