feat: introduce link tag filter hook (#71)

* fix: Do not generate link tags when both prefetch+preload are set to false

Fixes: #70

* feat: introduce link filter hook

Using this hook a hook can be set that allows for
filtering the list of link tags that are generated
by this plugin. The hook can both supress generating
link tags or modify the contents of the links.

Fixes: #7
Fixes: #10

Author: BenBE

src/index.ts

@@ -87,7 +87,13 @@ export default createUnplugin<Options | undefined>((userOptions) => {
         handler: (html, ctx) => {
           const tags = getHeadLinkTags(options)
           const files = Object.keys(ctx.bundle ?? {}).filter(key => fontFileRegex.test(key))
+          const { prefetch: wantPrefetch, preload: wantPreload } = options?.custom || {}
           for (const file of files) {
+            if (!(
+              wantPrefetch === true || wantPreload === true ||
+              (wantPrefetch === undefined && wantPreload === undefined)
+            ))
+              continue
             const ext = extname(file)
             tags.push({
               tag: 'link',
@@ -101,7 +107,16 @@ export default createUnplugin<Options | undefined>((userOptions) => {
               },
             })
           }
-          return tags
+          let tagsReturned = tags
+          if (options?.custom?.linkFilter) {
+            const newTags: object[] | boolean = options?.custom?.linkFilter(tags)
+            if (Array.isArray(newTags)) {
+              tagsReturned = newTags
+            } else {
+              tagsReturned = newTags ? tags : []
+            }
+          }
+          return tagsReturned
         },
       },
     },
@@ -121,7 +136,14 @@ function generateVitepressBundle(
 
   const tags = getHeadLinkTags(options)
   const files = Object.keys(bundle ?? {}).filter(key => fontFileRegex.test(key))
+  const { prefetch: wantPrefetch, preload: wantPreload } = options?.custom || {}
   for (const file of files) {
+    if (!(
+      wantPrefetch === true || wantPreload === true ||
+      (wantPrefetch === undefined && wantPreload === undefined)
+    ))
+      continue
+
     const ext = extname(file)
     tags.push({
       tag: 'link',
@@ -136,7 +158,17 @@ function generateVitepressBundle(
     })
   }
 
-  for (const tag of tags) {
+  let tagsReturned = tags
+  if (options?.custom?.linkFilter) {
+    const newTags: object[] | boolean = options?.custom?.linkFilter(tags)
+    if (Array.isArray(newTags)) {
+      tagsReturned = newTags
+    } else {
+      tagsReturned = newTags ? tags : []
+    }
+  }
+
+  for (const tag of tagsReturned) {
     vitepressConfig?.site?.head?.push([
       tag.tag,
       tag.attrs?.onload === 'this.rel=\'stylesheet\''

src/types.ts

@@ -97,6 +97,13 @@ export interface CustomFonts {
    */
   prefetch?: boolean
   prefetchPrefix?: string
+  /**
+   * Provides a hook for filtering which `<link>` tags should be actually
+   * generated.
+   * @default true
+   */
+  linkFilter?: (tags: object[]) => object[] | boolean
+
   /**
    * @default: 'head-prepend'
    */