A custom node for Unity's ShaderGraph to capture lighting and use it into the shader. Works as of July 2018, but the APIs might change!

MainLightNode.cs

//This API to create new nodes has been deprecated in early 2019.
//This means that if you are on a more recent version of Shader Graph and Universal Render Pipeline, you should use instead a pre-made node, which acts like a container that allows you to inject custom HLSL code into Shader Graph without the need to create a node from scratch.
//Please use the new node, not the C# API described here.
//
//You can find more details about that node in the Docs: https://docs.unity3d.com/Packages/com.unity.shadergraph@6.7/manual/Custom-Function-Node.html
//I also blogged about it here: https://connect.unity.com/p/adding-your-own-hlsl-code-to-shader-graph-the-custom-function-node
//
//If you are still on a very old version of Lightweight Render Pipeline (you shouldn't!!), you can still see the C# code for this custom node by rolling back to a previous version.

@earthtojens First off, looking for an answer to your problem I accidently ran into this page which is honestly more hidden that it should be: Custom node documentation (may come in handy).
Secondly, I'm assuming you didn't put 'Light' in the name field of the custom function as this would give a similar error.

Just make this a little clearer, if you call your function "Main Light" you'll get this error, where as "MainLight" is perfectly fine. I guess space in the custom function name is not allowed.

Hey everyone, as I reported in the gist itself, the API described here is really obsolete now. Please refer to this blog post for the explanation: https://connect.unity.com/p/adding-your-own-hlsl-code-to-shader-graph-the-custom-function-node

As such, I hid the code. You shouldn't use it if you're in a recent version of Universal Render Pipeline. Please use the Custom Function Node instead: https://docs.unity3d.com/Packages/com.unity.shadergraph@6.7/manual/Custom-Function-Node.html