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debug logging #33

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debug logging #33

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7e8ed6a
first pass at a debug logging implementation
max-mapper Nov 18, 2014
7445786
simplify context logic, use regex for matching env var
max-mapper Nov 18, 2014
73b2cea
add ids to streams for saner logging
max-mapper Nov 19, 2014
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27 changes: 27 additions & 0 deletions through2.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,20 @@ var Transform = require('readable-stream/transform')
, inherits = require('util').inherits
, xtend = require('xtend')

var debug = process.env['DEBUG'] || ''
var DEBUG = (debug === '*') || (debug === 'through2')
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maybe (debug === '*') || (/through2/.test(debug)) so you can do DEBUG=through2,another-module

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cool, updated in max-mapper@7445786


function DestroyableTransform(opts) {
Transform.call(this, opts)
this._destroyed = false
if (DEBUG) {
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for perf reasons you probably want to put the content of this if inside a function to avoid these functions being hoisted

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it would only happen once though at the time of stream construction, do you think that would make a noticeable perf impact?

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true, probably not

this.on('finish', function() {
console.error(' through2 finish')
})
this.on('end', function() {
console.error(' through2 end')
})
}
}

inherits(DestroyableTransform, Transform)
Expand Down Expand Up @@ -50,8 +61,11 @@ function through2 (construct) {

// main export, just make me a transform stream!
module.exports = through2(function (options, transform, flush) {
if (DEBUG) console.error(' through2 initialize')

var t2 = new DestroyableTransform(options)

if (DEBUG) transform = debugTransform(transform, t2)
t2._transform = transform

if (flush)
Expand All @@ -64,6 +78,8 @@ module.exports = through2(function (options, transform, flush) {
// make me a reusable prototype that I can `new`, or implicitly `new`
// with a constructor call
module.exports.ctor = through2(function (options, transform, flush) {
if (DEBUG) console.error(' through2.ctor initialize')

function Through2 (override) {
if (!(this instanceof Through2))
return new Through2(override)
Expand All @@ -75,6 +91,7 @@ module.exports.ctor = through2(function (options, transform, flush) {

inherits(Through2, DestroyableTransform)

if (DEBUG) transform = debugTransform(transform)
Through2.prototype._transform = transform

if (flush)
Expand All @@ -85,12 +102,22 @@ module.exports.ctor = through2(function (options, transform, flush) {


module.exports.obj = through2(function (options, transform, flush) {
if (DEBUG) console.error(' through2.obj initialize')

var t2 = new DestroyableTransform(xtend({ objectMode: true, highWaterMark: 16 }, options))

if (DEBUG) transform = debugTransform(transform, t2)
t2._transform = transform

if (flush)
t2._flush = flush

return t2
})

function debugTransform(transform, ctx) {
return function debugTransform(chunk, enc, callback) {
console.error(' through2 transform', typeof chunk, {length: chunk.length, encoding: enc})
transform.apply(ctx || this, arguments)
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this should always be this

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good call, I dont know what I was thinking

}
}