Trait Plugin 

pub trait Plugin:
    Debug
    + Send
    + Sync {
    // Required method
    fn name(&self) -> &str;

    // Provided methods
    fn before_compile(&self, _ctx: &PluginContext) -> Result<(), SsgError> { ... }
    fn after_compile(&self, _ctx: &PluginContext) -> Result<(), SsgError> { ... }
    fn transform_html(
        &self,
        html: &str,
        _path: &Path,
        _ctx: &PluginContext,
    ) -> Result<String, SsgError> { ... }
    fn has_transform(&self) -> bool { ... }
    fn needs_all_files(&self) -> bool { ... }
    fn on_serve(&self, _ctx: &PluginContext) -> Result<(), SsgError> { ... }
}

Trait for SSG plugins.

Implement this trait to create a plugin that hooks into the site generation lifecycle. All hooks have default no-op implementations, so you only need to override the ones you care about.

Stability contract

This trait is part of the SSG public API. The stability commitment for the 1.0 line is:

1. All current hook signatures are frozen. Once 1.0 ships, no parameter, return type, or trait bound on an existing method will change without a major version bump.
2. New hooks land with a default Ok(()) implementation. Adding a new hook is therefore non-breaking — existing impl Plugin for … blocks continue to compile.
3. PluginContext is #[non_exhaustive]. New fields (e.g. additional caches, link graphs, image metadata) can be added without breaking downstream construction sites — those are constructed inside SSG, not by plugin authors.
4. Removing a hook requires a major bump. Hook removal is rare and always preceded by a deprecation cycle of at least one minor release with #[deprecated] and a migration note in the CHANGELOG.

See API stability audit for the full Tier-A inventory.

Required Methods

fn name(&self) -> &str

Returns the unique name of this plugin.

Provided Methods

fn before_compile(&self, _ctx: &PluginContext) -> Result<(), SsgError>

Called before site compilation begins.

Use this hook to preprocess content files, inject metadata, or validate source directories.

fn after_compile(&self, _ctx: &PluginContext) -> Result<(), SsgError>

Called after site compilation completes.

Use this hook to post-process generated HTML, optimize assets, generate sitemaps, or perform any output transformation.

fn transform_html( &self, html: &str, _path: &Path, _ctx: &PluginContext, ) -> Result<String, SsgError>

Per-file HTML transform hook — called once per HTML file during the fused transform pass.

Receives the current HTML content and returns the (possibly modified) HTML. The default implementation returns the input unchanged.

Plugins that implement this hook avoid redundant file I/O — the pipeline reads each HTML file once, pipes it through all plugins’ transform_html hooks, then writes the result once.

fn has_transform(&self) -> bool

Returns true if this plugin implements transform_html. Override to true to opt in to the fused transform pass.

fn needs_all_files(&self) -> bool

Returns true if this plugin must always observe the full cache.html_files() list — even during --incremental rebuilds that only invalidated a handful of pages.

SEO sitemap regeneration, SBOM emission, JSON-LD aggregation, and search-index builders all need the complete view of the site to produce correct output, so they opt in to true (the default). Plugins that genuinely work per-file (and so can be skipped for unaffected pages) override to false. (Issue #524 AC7.)

fn on_serve(&self, _ctx: &PluginContext) -> Result<(), SsgError>

Called before the development server starts serving files.

Use this hook to inject dev-mode scripts, set up live-reload, or modify the serve directory.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl Plugin for AccessibilityPlugin

impl Plugin for AgentApiPlugin

impl Plugin for AgenticDiscoveryPlugin

impl Plugin for AiPlugin

impl Plugin for AtomFeedPlugin

impl Plugin for AuditPlugin

impl Plugin for CanonicalPlugin

impl Plugin for ContentValidationPlugin

impl Plugin for CspPlugin

impl Plugin for ssg::deploy::DeployPlugin

impl Plugin for ssg::plugins::DeployPlugin

impl Plugin for DraftPlugin

impl Plugin for EdgeHeadersPlugin

impl Plugin for FingerprintPlugin

impl Plugin for HighlightPlugin

impl Plugin for HtmlFixPlugin

impl Plugin for I18nPlugin

impl Plugin for ImageOptiPlugin

impl Plugin for ImageOptimizationPlugin

Available on crate feature image-optimization only.

impl Plugin for IslandPlugin

impl Plugin for IsrManifestPlugin

impl Plugin for JsonFeedPlugin

impl Plugin for JsonLdPlugin

impl Plugin for LiveReloadPlugin

impl Plugin for LlmPlugin

impl Plugin for LocalizedSearchPlugin

impl Plugin for ManifestFixPlugin

impl Plugin for MarkdownExtPlugin

impl Plugin for MinifyPlugin

impl Plugin for NewsSitemapFixPlugin

impl Plugin for OembedPlugin

impl Plugin for OgImagePlugin

impl Plugin for PaginationPlugin

impl Plugin for RobotsPlugin

impl Plugin for RpcSchemaPlugin

impl Plugin for RssAggregatePlugin

impl Plugin for ssg::postprocess::SbomPlugin

impl Plugin for ssg::sbom::SbomPlugin

impl Plugin for SearchPlugin

impl Plugin for SeoPlugin

impl Plugin for ShortcodePlugin

impl Plugin for SitemapFixPlugin

impl Plugin for TaxonomyPlugin

impl Plugin for TemplatePlugin

Available on crate feature templates only.

impl Plugin for VectorSearchPlugin

impl Plugin for ViewTransitionsPlugin