SPFx overclockers or how to significantly speed up the "gulp serve" command

A few months ago I wrote an article about SharePoint Framework build performance - SPFx overclockers or how to significantly improve your SharePoint Framework build performance. I've tried to reduce the amount of time the "gulp serve" command uses to re-build your code and to finally refresh a browser. I used different optimization technics for that purpose. The idea was to tweak the default SPFx build pipeline. However, those post only partially solves the problem. 

In this post, I will solve the problem from another way around (spoiler: I managed to make "serve" 10-15 times faster). 

The idea

How SharePoint Framework's "gulp serve" works? It gets your sources and outputs javascript bundles. But "gulp serve" becomes slow when your solution grows. How to fix that issue? Well, since it's slow, then don't use it! 

So this is the idea - don't use "gulp serve", use completely custom webpack based build to transform your sources into exactly the same javascript bundles which are produced by "gulp serve". 

What is the input for "gulp serve"? - TypeScript sources, styles. What is the output? - Javascript files. Can we get sources and produce exactly the same javascript? -Yes.

How it works

Some nerdy content goes below. If you don't want to read about internal implementation, go directly to "How can I use it?"

To make it work, we need custom webpack config and webpack dev server to serve webpack output. More...

SPFx overclockers or how to significantly improve your SharePoint Framework build performance

Please also check out this post - SPFx overclockers or how to significantly speed up the "gulp serve" command which uses different approach in performance tweaking and gives you extremely fast "serve" speed

Today's post will be about SharePoint Framework build performance. Especially about "serve" command, because it's the most frequently used command among developers. gulp serve is a kind of "watch" mode for your SharePoint Framework solution. As soon as you update a file, it will spin up the build process and will refresh your browser finally, so that you can see changes.

However, from here and there, I hear complaints about the poor performance of gulp serve command, especially if you have more than 10 web parts in a solution, or if your webparts are quite complicated (with lots of code and \ or additional heavy dependencies). Checkout Gulp webpack slow build and Long build times for SPFx projects with many components GitHub issues as well. I'm also not satisfied with the build performance in case of medium and of course big SharePoint Framework solutions. In a few recent weeks, I spent some time trying to go deeper and understanding all possible ways on how to improve performance for gulp serve command.

Read further and you will find a list of tricks, which reduce the amount of time to build a common SharePoint Framework solution. By build I mean serve or bundle (without --ship parameter) command, because they are very identical. The only difference is that serve is never-ending and has an additional step which refreshes your browser. In all other cases, they are the same, running tslint, typescript, sass, webpack, copy assets, etc. tasks. I will start with the easiest tricks, going to more complicated technics. I don't use any heavy hacks here. 

At the end of the post, you will find a detailed report on how any particular trick reduces build time on the example of SharePoint Starter Kit:

This is a solution designed for SharePoint Online which provides numerous web parts, extensions, and other components which you can use as an example and inspiration for your own customizations.

It contains 20+ webparts and quite slow when you use gulp serve command. Which makes it a good candidate for improvements. More...