@ledgerhq/logs

What is @ledgerhq/logs?

@ledgerhq/logs is an npm package designed to facilitate logging within applications that interact with Ledger hardware wallets. It provides a simple and consistent way to log messages, which can be useful for debugging and monitoring the behavior of applications.

What are @ledgerhq/logs's main functionalities?

Basic Logging

This feature allows you to log messages with a specific type and level. In this example, 'apdu' is the type, 'message' is the content, and 'debug' is the level of the log.

const { log } = require('@ledgerhq/logs');
log('apdu', 'message', 'debug');

Custom Log Listener

You can set up a custom listener to handle log messages. This example demonstrates how to listen for log events and print them to the console.

const { listen } = require('@ledgerhq/logs');
listen(log => {
  console.log(log.type, log.message, log.level);
});

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README

@ledgerhq/logs

Utility library that is used by all Ledger libraries to dispatch logs so we can deal with them in a unified way.

API

Table of Contents

• Log
  • type
  • data
  • context
  • id
• log
  • Parameters
• trace
  • Parameters
• LocalTracer
  • Parameters
  • withType
    • Parameters
  • withContext
    • Parameters
  • withUpdatedContext
    • Parameters
• listen
  • Parameters

Log

A Log object

type

A namespaced identifier of the log (not a level like "debug", "error" but more like "apdu", "hw", etc...)

Type: LogType

data

Data associated to the log event

Type: LogData

context

Context data, coming for example from the caller's parent, to enable a simple tracing system

Type: TraceContext

id

Unique id among all logs

Type: string

log

Logs something

Parameters

• type LogType a namespaced identifier of the log (it is not a level like "debug", "error" but more like "apdu-in", "apdu-out", etc...)
• message string? a clear message of the log associated to the type
• data LogData?

trace

A simple tracer function, only expanding the existing log function

Its goal is to capture more context than a log function. This is simple for now, but can be improved later.

Parameters

• context {type: LogType, message: string?, data: LogData?, context: TraceContext?} Anything representing the context where the log occurred

  • context.type
  • context.message
  • context.data
  • context.context

LocalTracer

A simple tracer class, that can be used to avoid repetition when using the trace function

Its goal is to capture more context than a log function. This is simple for now, but can be improved later.

Parameters

• ``
• ``
• type A given type (not level) for the current local tracer ("hw", "withDevice", etc.)
• context Anything representing the context where the log occurred

withType

Create a new instance of the LocalTracer with an updated type

It does not mutate the calling instance, but returns a new LocalTracer, following a simple builder pattern.

Parameters

• type LogType

Returns LocalTracer

withContext

Create a new instance of the LocalTracer with a new context

It does not mutate the calling instance, but returns a new LocalTracer, following a simple builder pattern.

Parameters

• context TraceContext? A TraceContext, that can undefined to reset the context

Returns LocalTracer

withUpdatedContext

Create a new instance of the LocalTracer with an updated context, on which an additional context is merged with the existing one.

It does not mutate the calling instance, but returns a new LocalTracer, following a simple builder pattern.

Parameters

• contextToAdd TraceContext

Returns LocalTracer

listen

Adds a subscribers to the emitted logs.

Parameters

• cb Subscriber that is called for each future log() with the Log object

Returns Unsubscribe a function that can be called to unsubscribe the listener