halo-dark-mode-plugin/.agents/skills/halo-theme-dev/references/annotations.md

Model Metadata (Annotations)

Themes can extend built-in Halo models with custom fields via AnnotationSetting resources (e.g. adding an icon to menu items, or a download URL to posts), then read those values in templates via the #annotations utility.

Defining a Metadata Form (AnnotationSetting)

Create a file (any name) in the theme root, e.g. annotation-setting.yaml, and declare an AnnotationSetting resource:

apiVersion: v1alpha1
kind: AnnotationSetting
metadata:
  name: theme-foo-menuitem-abc123 # recommended: add theme prefix + random suffix to avoid conflicts
spec:
  targetRef:
    group: ""
    kind: MenuItem
  formSchema:
    - $formkit: text
      name: icon
      label: Menu icon class
      value: ""

Multiple models can be declared in the same file separated by ---:

apiVersion: v1alpha1
kind: AnnotationSetting
metadata:
  name: theme-foo-post-abc123
spec:
  targetRef:
    group: content.halo.run
    kind: Post
  formSchema:
    - $formkit: text
      name: download_url
      label: Download URL
      value: ""

---
apiVersion: v1alpha1
kind: AnnotationSetting
metadata:
  name: theme-foo-menuitem-abc123
spec:
  targetRef:
    group: ""
    kind: MenuItem
  formSchema:
    - $formkit: text
      name: icon
      label: Icon
      value: ""

Supported Models

Model	group	kind
Post	content.halo.run	Post
Single page	content.halo.run	SinglePage
Post category	content.halo.run	Category
Post tag	content.halo.run	Tag
Menu item	""	MenuItem
User	""	User

Notes

• All values in metadata.annotations are strings, so form values must also be strings.
• Do not use components with non-string output such as number, group, or repeater.
• For checkbox, explicitly set on-value / off-value to string values (e.g. "true" / "false").
• Use a theme-name prefix plus a random suffix for metadata.name to avoid conflicts with other themes/plugins, e.g. theme-earth-post-wanfs5.

Reading Metadata in Templates

Halo provides a #annotations utility object in Thymeleaf with three methods:

#annotations.get(object, key) — Get a value

<div th:with="menu = ${menuFinder.getPrimary()}">
  <li th:each="item : ${menu.menuItems}">
    <i th:class="${#annotations.get(item, 'icon')}"></i>
    <a th:href="${item.status.href}" th:text="${item.status.displayName}"></a>
  </li>
</div>

#annotations.getOrDefault(object, key, defaultValue) — Get a value with fallback

<i th:class="${#annotations.getOrDefault(menuItem, 'icon', 'fa fa-link')}"></i>

#annotations.contains(object, key) — Check if a key exists

<i
  th:if="${#annotations.contains(menuItem, 'icon')}"
  th:class="${#annotations.get(menuItem, 'icon')}"
></i>

Online Docs

AnnotationSetting spec and supported models may change across Halo versions. Fetch the relevant doc if unsure about supported group/kind combinations or form schema constraints.

• Using metadata in templates: https://raw.githubusercontent.com/halo-dev/docs/refs/heads/main/docs/developer-guide/theme/annotations.md
• Defining annotation forms: https://raw.githubusercontent.com/halo-dev/docs/refs/heads/main/docs/developer-guide/annotations-form.md