fix(unhead): safer removal of leading / trailing separators

harlan-zw · harlan-zw · commit d450124a6e90 · 2025-07-31T19:02:53.000+10:00
Fixes #561
diff --git a/packages/unhead/src/utils/templateParams.ts b/packages/unhead/src/utils/templateParams.ts
@@ -1,7 +1,6 @@
 import type { TemplateParams } from '../types'
 
 const SepSub = '%separator'
-const SepSubRE = new RegExp(`${SepSub}(?:\\s*${SepSub})*`, 'g')
 
 // for each %<word> token replace it with the corresponding runtime config or an empty value
 function sub(p: TemplateParams, token: string, isJson = false) {
@@ -61,12 +60,10 @@ export function processTemplateParams(s: string, p: TemplateParams, sep?: string
   // we need to remove separators if they're next to each other or if they're at the start or end of the string
   // for example: %separator %separator %title should return %title
   if (hasSepSub) {
-    if (s.endsWith(SepSub))
-      s = s.slice(0, -SepSub.length)
-    if (s.startsWith(SepSub))
-      s = s.slice(SepSub.length)
-    // make sure we don't have two separators next to each other
-    s = s.replace(SepSubRE, sep || '').trim()
+    s = s.split(SepSub)
+      .map(part => part.trim())
+      .filter(Boolean)
+      .join(` ${sep || ''} `)
   }
   return s
 }
diff --git a/packages/unhead/test/unit/client/templateParams.test.ts b/packages/unhead/test/unit/client/templateParams.test.ts
@@ -220,4 +220,30 @@ describe('templateParams', () => {
       </body></html>"
     `)
   })
+
+  it('edge case #561', async () => {
+    const dom = useDom({
+      headTags: '<title>Vite</title>',
+    })
+    const head = createClientHeadWithContext({
+      document: dom.window.document,
+      plugins: [TemplateParamsPlugin],
+    })
+    // The test should ensure that:
+    // 1. The existing title "Vite" is captured as %s
+    // 2. Empty string companyName stays empty (not converted to true)
+    // 3. The separator adjacent to empty values should be removed
+    useHead(head, {
+      titleTemplate: `%s %separator %companyName %separator %siteTitle`,
+      templateParams: {
+        companyName: '',
+        siteTitle: 'Site title',
+      },
+    })
+    const html = await new Promise<string>((resolve) => {
+      setTimeout(() => resolve(dom!.serialize()), 250)
+    })
+
+    expect(html).toContain('<title>Site title</title>')
+  })
 })
