set page canonical link (#1055)

Author: maxence-charriere

pkg/app/http.go

@@ -688,6 +688,11 @@ func (h *Handler) servePage(w http.ResponseWriter, r *http.Request) {
 						Content(v)
 				}),
 				Title().Text(page.Title()),
+				If(page.canonicalLink != "", func() UI {
+					return Link().
+						Rel("canonical").
+						Href(resolveOGResource(h.Domain, page.canonicalLink))
+				}),
 				Range(h.Preconnect).Slice(func(i int) UI {
 					if resource := parseHTTPResource(h.Preconnect[i]); resource.URL != "" {
 						return resource.toLink().Rel("preconnect")

pkg/app/page.go

@@ -65,6 +65,9 @@ type Page interface {
 
 	// Set the Twitter card.
 	SetTwitterCard(v TwitterCard)
+
+	// Set the page's canonical link.
+	SetCanonicalLink(format string, v ...any)
 }
 
 type requestPage struct {
@@ -79,6 +82,7 @@ type requestPage struct {
 	preloads       []Preload
 	loadingLabel   string
 	image          string
+	canonicalLink  string
 	width          int
 	height         int
 	twitterCardMap map[string]string
@@ -173,6 +177,12 @@ func (p *requestPage) SetTwitterCard(v TwitterCard) {
 	p.twitterCardMap = v.toMap()
 }
 
+func (p *requestPage) SetCanonicalLink(format string, v ...any) {
+	if canonicalLink := FormatString(format, v...); canonicalLink != "" {
+		p.canonicalLink = p.resolveURL(canonicalLink)
+	}
+}
+
 type browserPage struct {
 	resolveURL func(string) string
 }
@@ -283,6 +293,9 @@ func (p browserPage) SetTwitterCard(v TwitterCard) {
 	}
 }
 
+func (p browserPage) SetCanonicalLink(format string, v ...any) {
+}
+
 func (p browserPage) metaByName(v string) Value {
 	meta := Window().
 		Get("document").

pkg/app/page_test.go

@@ -57,4 +57,5 @@ func testPage(t *testing.T, p Page) {
 	require.NotZero(t, h)
 
 	p.SetTwitterCard(TwitterCard{Card: "summary"})
+	p.SetCanonicalLink("/canon")
 }