Hi,

I noticed that our incremental builds started to be considerably slower than they used to, so I ran webpack with --profile --progress and older versions of ts-loader to see if there are differences. It seems that v0.5.2 is twice as fast as the latest version. I'm unsure how to interpret the profiling data and the webpack source code is a complete mess, so it doesn't help much in that regard.

Here are the stats:

// ts-loader v0.5.2
379ms build modules   
19ms seal
39ms optimize
60ms hashing
35ms create chunk assets
2ms additional chunk assets 
0ms optimize chunk assets 
0ms optimize assets 
99ms emit
Hash: fdd096aa48ded051dda3
Version: webpack 1.12.2
Time: 639ms

// ts-loader v0.5.6
357ms build modules   
19ms seal
50ms optimize
51ms hashing
40ms create chunk assets
4ms additional chunk assets 
0ms optimize chunk assets 
826ms optimize assets
78ms emit
Hash: fdd096aa48ded051dda3
Version: webpack 1.12.2
Time: 1429ms

It looks like there is a lot of time spent in "optimize assets". I don't know what's causing this, but I have a feeling that ts-loader is using some extra dependencies now which may have the side-effect of enabling some webpack optimizations that are meant for production, not development.