Log an error object along with context-specific error message

[raine]

Hello,

Thanks for a great library.

I want to log an error object along with a message that describes the context of the error.

log.error('Error while doing x', err)

However, that results in

[error] Error while doing x

I'm aware you can do log.error(err), which results in a nice log message of the error, but most of time I actually want to include a custom message, without logging two lines.

What if log.error('Error while doing x', err) printed the following?

[error]: Error while doing x error="[object Object]" stack="TypeError: Cannot read prope
rty 'length' of null
    at redis.mgetAsync.then.then
message="Cannot read property 'length' of null"

[ianstormtaylor]

Sounds great to me!

[raine]

How do you feel about this?

try {
  JSON.parse('#')
} catch (err) {
  log.error('failed to parse json', err)
}

[error] failed to parse json message="Unexpected token # in JSON at position 0" stack="SyntaxError: Unexpected token # in JSON at position 0
    at JSON.parse (<anonymous>)

If this makes sense to you, I'll open a PR.

---

Another example that shows how extra properties of Error are merged to data as well.

log.error('failed to update podcast', err)

error] failed to update podcast message="column \"sumary\" of relation \"podcast\" does not exist" stack="error: column \"sumary\" of relation \"podcast\" does not exist
   at Connection.parseE (/node_modules/pg/lib/connection.js:602:11)
   at Connection.parseMessage (/node_modules/pg/lib/connection.js:399:19)
   at Socket.<anonymous> (/node_modules/pg/lib/connection.js:121:22)
   at Socket.emit (events.js:189:13)
   at Socket.EventEmitter.emit (domain.js:441:20)
   at addChunk (_stream_readable.js:284:12)
   at readableAddChunk (_stream_readable.js:265:11)
   at Socket.Readable.push (_stream_readable.js:220:10)
   at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)" name=error length=128 severity=ERROR code=42703 detail= hint= position=40 internalPosition= internalQuery= where= schema= table= column= dataType= constraint= file=analyze.c line=2346 routine=transformUpdateTargetList

[ianstormtaylor]

@raine sounds good to me! As close as possible to the existing log.error(e) behavior but with the updated message would be good.