added template.Registry.LoadFS method

tools/template/registry_test.go

@@ -1,6 +1,7 @@
 package template
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
@@ -138,3 +139,78 @@ func TestRegistryLoadString(t *testing.T) {
 		}
 	})
 }
+
+func TestRegistryLoadFS(t *testing.T) {
+	r := NewRegistry()
+
+	t.Run("invalid fs", func(t *testing.T) {
+		fs := os.DirFS("__missing__")
+
+		files := []string{"missing1", "missing2"}
+
+		key := fmt.Sprintf("%v%v", fs, files)
+
+		r.LoadFS(fs, files...)
+
+		renderer := r.cache.Get(key)
+
+		if renderer == nil {
+			t.Fatal("Expected renderer to be initialized even if invalid, got nil")
+		}
+
+		if renderer.template != nil {
+			t.Fatalf("Expected renderer template to be nil, got %v", renderer.template)
+		}
+
+		if renderer.parseError == nil {
+			t.Fatalf("Expected renderer parseError to be set, got nil")
+		}
+	})
+
+	t.Run("valid fs", func(t *testing.T) {
+		// create test templates
+		dir, err := os.MkdirTemp(os.TempDir(), "template_test2")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, "base.html"), []byte(`Base:{{template "content"}}`), 0644); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, "content.html"), []byte(`{{define "content"}}Content:123{{end}}`), 0644); err != nil {
+			t.Fatal(err)
+		}
+		defer os.RemoveAll(dir)
+
+		fs := os.DirFS(dir)
+
+		files := []string{"base.html", "content.html"}
+
+		key := fmt.Sprintf("%v%v", fs, files)
+
+		r.LoadFS(fs, files...)
+
+		renderer := r.cache.Get(key)
+
+		if renderer == nil {
+			t.Fatal("Expected renderer to be initialized even if invalid, got nil")
+		}
+
+		if renderer.template == nil {
+			t.Fatal("Expected renderer template to be set, got nil")
+		}
+
+		if renderer.parseError != nil {
+			t.Fatalf("Expected renderer parseError to be nil, got %v", renderer.parseError)
+		}
+
+		result, err := renderer.Render(nil)
+		if err != nil {
+			t.Fatalf("Unexpected Render() error, got %v", err)
+		}
+
+		expected := "Base:Content:123"
+		if result != expected {
+			t.Fatalf("Expected Render() result %q, got %q", expected, result)
+		}
+	})
+}