Hook System

GoPress hooks are the Go equivalent of WordPress do_action and apply_filters. They are the primary way plugins and themes extend core without importing one another.

API

// Action: side effects only.
e.Hooks.AddAction(name, fn, priority) hook.Handle
e.Hooks.RemoveAction(handle)
e.Hooks.DoAction(ctx, name, args...)

// Filter: transform one value through an ordered chain.
e.Hooks.AddFilter(name, fn, priority) hook.Handle
e.Hooks.RemoveFilter(handle)
e.Hooks.ApplyFilter(name, value, args...) interface{}

Lower priority numbers run first. Every registration returns a hook.Handle; plugins must retain those handles and remove them during Deactivate so runtime disable is complete.

Hook names and payloads are public contracts. Keep payloads stable and generic; do not expose a theme-private struct or provider SDK type to the other side. A filter with no subscribers must return its input unchanged, and an action with no subscribers must have no effect.

Engine Lifecycle Hooks

Hook	Timing	Arguments
`engine.init`	After bootstrap completes.	`*core.Engine`
`middleware.early`	Before page-cache middleware.	`*gin.Engine`
`routes.register`	After admin routes and before the frontend catch-all.	`*gin.Engine`
`options.bulk_updated`	After admin saves options in bulk.	None

Theme Template Slots

Plugins contribute local frontend HTML through semantic slots declared by the theme:

Hook	Go constant	Location and typical use
`header.nav.after`	`hook.ThemeHeaderNavAfter`	End of the primary navigation list; language switchers or account menus.
`theme.head.end`	`hook.ThemeHeadEnd`	Before `</head>`; verification meta, analytics, preconnect, or CSS.
`theme.body.open`	`hook.ThemeBodyOpen`	Immediately after `<body>`; noscript tags, bootstrap code, or banners.
`theme.footer.end`	`hook.ThemeFooterEnd`	Before `</body>` after theme scripts; deferred scripts or widgets.

<ul class="nav-menu">
  {{$homeURL := langPrefixURL .Ctx "/"}}
  <li><a href="{{$homeURL}}" class="{{if isMenuURLActive .Ctx $homeURL}}active{{end}}">{{T .Ctx "nav_home"}}</a></li>
  {{renderHook "header.nav.after" .}}
</ul>

Global slots belong in the base layout and should appear exactly once:

<head>
  ...
  {{renderHook "theme.head.end" .}}
</head>
<body>
  {{renderHook "theme.body.open" .}}
  ...
  {{renderHook "theme.footer.end" .}}
</body>

See Theme Frontend Slots.

Hook	Go constant	Contract
`menu.location.resolve`	`hook.MenuLocationResolve`	Filter after location lookup. Value: `*menu.Menu`; args: `location string`.
`menu.deleted`	`hook.MenuDeleted`	Action after deletion. Args: `menuID uint`.

Language-aware menu assignment is implemented through these generic hooks; core/menu has no multilingual-specific branch.

Admin Extension Hooks

Hook	Go constant	Contract
`admin.content_list.tabs`	`admin.HookContentListTabs`	Filter list tabs. Value: `[]admin.ContentListTab`; args: `*gin.Context, typeName string`.
`admin.content.permalink_prefix`	`admin.HookContentPermalinkPrefix`	Filter an editor permalink prefix. Value: `string`; args: `gin.Context, content.Content`.
`admin.content_form.fields`	`hook.AdminContentFormFields`	Filter editor meta-box HTML. Value: `template.HTML`; args: `content.Content, content.ContentTypeDef`.
`admin.content.saved`	`hook.AdminContentSaved`	Action after the content row is saved. Args: `gin.Context, content.Content`.

See Admin Extension Points.

SEO Hook

seo.content.meta (hook.SEOContentMeta) filters a single content page's rewrite.SEOMeta before rendering. Its arguments are the content row and its metadata map. The SEO Extras plugin is the reference implementation.

Sitemap Transformers

type TransformerHandle
handle := e.Sitemap.AddTransformer(fn)
e.Sitemap.RemoveTransformer(handle)

A transformer can add alternate-language links or derived URL entries. The remove handle provides the same hot-disable guarantee as actions and filters.

Extension Pattern

Core defines the data contract, hook name, and trigger point.
A plugin registers actions or filters during activation and saves handles.
With no plugin, filters pass values through and actions have no side effects.
Deactivation removes every handle and any symmetric transformer registration.

This pattern keeps core complete on its own while allowing features to be composed without theme/plugin cross-dependencies.