serve language variants under a prefix

The default locale stays at the root; every other language is the same key under /{lang}/ (ADR-0009). /en/… is never live and redirects to the root form so the URL space cannot fork. Lookup now takes a language and reports which one it served, following requested → default → any rather than 404ing when a translation is missing. That is the second routing case, so the resolver is extracted to resolve.go and the mux keeps one entry: URL shape is the resolver's business. A leading segment counts as a language only when some bundle is written in it, so an unknown prefix is a 404 rather than a stripped path — and a section may not be named after a language in use, now recorded in content-model.md. Because the served variant can differ from the URL requested, Page gained .Canonical (the variant actually served) and .Alternates for hreflang. A theme must never build a path, so both come from the engine. Evidence: /bn/pages/about/ serves the Bengali body with lang="bn" and canonical /bn/pages/about/; /bn/posts/hello-world/ falls back to English with canonical /posts/hello-world/; /en/pages/about/ 301s to /pages/about/; /fr/… is 404.
2026-08-01 02:23:34 +06:00
parent c6d5b4abb7
commit 80057aa183
12 changed files with 301 additions and 47 deletions
@@ -69,3 +69,95 @@ func TestUnknownPathsAre404(t *testing.T) {
 		}
 	}
 }
+
+func multilingualHandler(t *testing.T) http.Handler {
+	t.Helper()
+	fsys := fstest.MapFS{
+		"content/pages/about.md":    {Data: []byte("---\ntitle: About\n---\nEnglish.\n")},
+		"content/pages/about.bn.md": {Data: []byte("---\ntitle: পরিচিতি\n---\nবাংলা।\n")},
+		"content/pages/now.md":      {Data: []byte("---\ntitle: Now\n---\nOnly English.\n")},
+	}
+	bundles, err := content.Scan(fsys)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r, err := render.New()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return Handler(content.NewSite(bundles), r)
+}
+
+func TestPrefixedLanguageServesThatVariant(t *testing.T) {
+	h := multilingualHandler(t)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/bn/pages/about/", nil))
+	if rec.Code != http.StatusOK {
+		t.Fatalf("got %d, want 200", rec.Code)
+	}
+	body := rec.Body.String()
+	if !strings.Contains(body, "বাংলা।") || !strings.Contains(body, `lang="bn"`) {
+		t.Errorf("did not serve the Bengali variant:\n%s", body)
+	}
+	if !strings.Contains(body, `rel="canonical" href="/bn/pages/about/"`) {
+		t.Error("canonical should name the variant actually served")
+	}
+	if !strings.Contains(body, `hreflang="en" href="/pages/about/"`) {
+		t.Error("hreflang should list the English variant at the root form")
+	}
+}
+
+func TestMissingVariantFallsBackAndSaysSo(t *testing.T) {
+	h := multilingualHandler(t)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/bn/pages/now/", nil))
+	if rec.Code != http.StatusOK {
+		t.Fatalf("got %d, want 200: the fallback chain must not 404 (ADR-0009)", rec.Code)
+	}
+	body := rec.Body.String()
+	if !strings.Contains(body, "Only English.") {
+		t.Error("expected the English body as fallback")
+	}
+	if !strings.Contains(body, `rel="canonical" href="/pages/now/"`) {
+		t.Error("canonical must point at the variant served, not the URL requested")
+	}
+}
+
+func TestDefaultLanguagePrefixRedirectsToRoot(t *testing.T) {
+	h := multilingualHandler(t)
+	for path, want := range map[string]string{
+		"/en/pages/about/": "/pages/about/",
+		"/en/pages/about":  "/pages/about/",
+	} {
+		rec := httptest.NewRecorder()
+		h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, path, nil))
+		if rec.Code != http.StatusMovedPermanently {
+			t.Errorf("GET %s = %d, want 301: /en/… must never be live (ADR-0009)", path, rec.Code)
+			continue
+		}
+		if loc := rec.Header().Get("Location"); loc != want {
+			t.Errorf("GET %s → %q, want %q", path, loc, want)
+		}
+	}
+}
+
+func TestPrefixedSlashlessPathRedirectsWithItsPrefix(t *testing.T) {
+	h := multilingualHandler(t)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/bn/pages/about", nil))
+	if rec.Code != http.StatusMovedPermanently {
+		t.Fatalf("got %d, want 301", rec.Code)
+	}
+	if loc := rec.Header().Get("Location"); loc != "/bn/pages/about/" {
+		t.Errorf("Location = %q, want /bn/pages/about/", loc)
+	}
+}
+
+func TestUnknownLanguagePrefixIsNotALanguage(t *testing.T) {
+	h := multilingualHandler(t)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/fr/pages/about/", nil))
+	if rec.Code != http.StatusNotFound {
+		t.Errorf("got %d, want 404: fr is not a language this site has", rec.Code)
+	}
+}