Plugins and Slots

Plugins extend Kiln's functionality without modifying core code. Slots are the extension points where plugins hook in.

What are Slots?

Slots are predefined hook points in Kiln's build pipeline where custom logic runs:

Creating a Plugin

A plugin is a .NET class implementing IKilnPlugin:

using Kiln.Core.Plugins;
                
                public class MyCustomPlugin : IKilnPlugin
                {
                    public string Name => "My Custom Plugin";
                    public string Version => "1.0.0";
                
                    public void Register(IPluginContext context)
                    {
                        context.OnSlot("content:loaded", OnContentLoaded);
                        context.OnSlot("build:after", OnBuildAfter);
                    }
                
                    private void OnContentLoaded(IContentMetadata metadata)
                    {
                        // Modify frontmatter here
                        if (metadata.Tags.Count == 0)
                        {
                            metadata.Tags.Add("untagged");
                        }
                    }
                
                    private void OnBuildAfter(IBuildContext context)
                    {
                        Console.WriteLine($"Build completed: {context.PagesGenerated} pages");
                    }
                }
                

Installing Plugins

Plugins can be distributed as:

1. NuGet Packages: Add to project dependencies
2. Local Assemblies: Place in plugins/ directory
3. Source Files: Include .cs files in plugin directory

Register plugins in site.yaml:

plugins:
                  - name: MyCustomPlugin
                    enabled: true
                

Plugin Use Cases

• SEO Optimization: Auto-generate meta tags, sitemaps
• Analytics: Track page generation, build time
• Media Processing: Resize images, generate WebP variants
• Validation: Check broken links, missing images
• Notifications: Alert on build failures, new posts

Filesystem Plugin Location

Kiln scans plugins/ directory for plugin assemblies:

plugins/
                ├── MyPlugin.dll
                ├── MyPlugin.pdb
                └── MyPlugin.deps.json
                

Plugin Discovery

Kiln automatically:

• Discovers plugins in plugins/ and registered NuGet packages
• Loads plugin assemblies
• Calls Register() on each plugin
• Executes slot handlers in order

Best Practices

• Keep it simple: Focus on one responsibility
• Document slots: Explain what data is available
• Handle errors: Don't crash the build
• Use meaningful names: Clear plugin and slot names
• Version your plugins: Semantic versioning

Plugins make Kiln infinitely extensible!