how does spfx get builded? how to build custom spfx generator

SPFx projects are built using a complex Build System that is an npm package. You can find it under node_modules folder under the name - @microsoft/sp-build-web

This package makes use of more packages. You can go into the node_moduels folder and look for packages named @microsoft/gulp-core-build*

The entire build system is built in Object oriented code with lots of classes and interfaces using TypeScript.

If you want to just customize the Build process then you can build custom tasks which are coded in the gulpfile.js.

On good article to learn is at - https://rencore.com/blog/extending-sharepoint-framework-build-process-custom-tasks/

Understanding the Build Process:

• SPFx Project Structure: The SPFx framework automatically handles much of the configuration. The config folder in your SPFx project contains JSON files (e.g., config.json, serve.json, etc.) that manage various aspects of the build and deployment process.

• Gulp Tasks: Even though your gulpfile.js might have limited code, SPFx uses default Gulp tasks like gulp serve, gulp build, and gulp bundle. These tasks are defined internally in the SPFx framework. You can explore them by checking the @microsoft/sp-build-web package, which contains these predefined tasks.

• Custom Gulp Tasks: If you want to add custom tasks, you can modify the gulpfile.js to include your own Gulp tasks. For example, you might add tasks to automate linting, testing, or other custom build steps.

• Creating Your Own Custom SPFx Generator: PNP SPFx Generator: The PnP (Patterns and Practices) SPFx generator is a popular tool that extends the default Yeoman generator provided by Microsoft. You can indeed create your own custom generator if you have specific requirements that aren’t met by existing tools.

• Involving SPFx in Your Node Project: To involve SPFx in a custom Node.js project, you could create a Node.js script that automates the creation of SPFx projects or components. This script could use the Yeoman environment to programmatically run generators (including custom ones you’ve created).

To build your own generator:

• Yeoman Generator: You can create a custom Yeoman generator by defining your own prompts, templates, and scaffolding logic. Extend SPFx Generator: You could extend the SPFx generator by forking the PnP generator or creating a new generator from scratch using Yeoman.