reduce allocs by re-using string builder

framework/h/base.go

@@ -5,17 +5,18 @@ import (
 	"net/http"
 	"reflect"
 	"runtime"
+	"strings"
 )
 
 type Headers = map[string]string
 
 type Partial struct {
 	Headers *Headers
-	Root    string
+	Root    *Element
 }
 
-func (p *Partial) Render() string {
-	return p.Root
+func (p *Partial) Render(builder *strings.Builder) {
+	p.Root.Render(builder)
 }
 
 type Page struct {
@@ -30,23 +31,23 @@ func NewPage(root Ren) *Page {
 	}
 }
 
-func NewPageWithHttpMethod(httpMethod string, root Ren) *Page {
+func NewPageWithHttpMethod(httpMethod string, root *Element) *Page {
 	return &Page{
 		HttpMethod: httpMethod,
 		Root:       root,
 	}
 }
 
-func NewPartialWithHeaders(headers *Headers, root Ren) *Partial {
+func NewPartialWithHeaders(headers *Headers, root *Element) *Partial {
 	return &Partial{
 		Headers: headers,
-		Root:    root.Render(),
+		Root:    root,
 	}
 }
 
-func NewPartial(root Ren) *Partial {
+func NewPartial(root *Element) *Partial {
 	return &Partial{
-		Root: root.Render(),
+		Root: root,
 	}
 }
 

framework/h/lifecycle.go

@@ -69,12 +69,12 @@ func Increment(amount int) JsCommand {
 
 func SetInnerHtml(r Ren) JsCommand {
 	// language=JavaScript
-	return JsCommand{Command: fmt.Sprintf("this.innerHTML = `%s`", r.Render())}
+	return JsCommand{Command: fmt.Sprintf("this.innerHTML = `%s`", Render(r))}
 }
 
 func SetOuterHtml(r Ren) JsCommand {
 	// language=JavaScript
-	return JsCommand{Command: fmt.Sprintf("this.outerHTML = `%s`", r.Render())}
+	return JsCommand{Command: fmt.Sprintf("this.outerHTML = `%s`", Render(r))}
 }
 
 func AddAttribute(name, value string) JsCommand {

framework/h/render.go

@@ -2,13 +2,15 @@ package h
 
 import (
 	"fmt"
+	"strings"
 	"time"
 )
 
 func Render(node Ren) string {
 	start := time.Now()
-	html := node.Render()
+	builder := &strings.Builder{}
+	node.Render(builder)
 	duration := time.Since(start)
 	fmt.Printf("render took %d microseconds\n", duration.Microseconds())
-	return html
+	return builder.String()
 }

framework/h/renderer.go

@@ -5,15 +5,13 @@ import (
 	"strings"
 )
 
-func (node *Element) Render() string {
-	builder := &strings.Builder{}
-
+func (node *Element) Render(builder *strings.Builder) {
 	// some elements may not have a tag, such as a Fragment
 	if node.tag != "" {
 		builder.WriteString("<" + node.tag)
 		builder.WriteString(" ")
 		for name, value := range node.attributes {
-			builder.WriteString(NewAttribute(name, value).Render())
+			NewAttribute(name, value).Render(builder)
 		}
 	}
 
@@ -34,9 +32,9 @@ func (node *Element) Render() string {
 	for _, child := range node.children {
 		switch child.(type) {
 		case *AttributeMap:
-			builder.WriteString(child.(*AttributeMap).Render())
+			child.Render(builder)
 		case *LifeCycle:
-			builder.WriteString(child.(*LifeCycle).Render())
+			child.Render(builder)
 		}
 	}
 
@@ -53,52 +51,42 @@ func (node *Element) Render() string {
 		case *LifeCycle:
 			continue
 		default:
-			builder.WriteString(child.Render())
+			child.Render(builder)
 		}
 	}
 
 	if node.tag != "" {
 		builder.WriteString("</" + node.tag + ">")
 	}
-
-	str := builder.String()
-	return str
 }
 
-func (a *AttributeR) Render() string {
-	return fmt.Sprintf(`%s="%s"`, a.Name, a.Value)
+func (a *AttributeR) Render(builder *strings.Builder) {
+	builder.WriteString(fmt.Sprintf(`%s="%s"`, a.Name, a.Value))
 }
 
-func (t *TextContent) Render() string {
-	return t.Content
+func (t *TextContent) Render(builder *strings.Builder) {
+	builder.WriteString(t.Content)
 }
 
-func (r *RawContent) Render() string {
-	return r.Content
+func (r *RawContent) Render(builder *strings.Builder) {
+	builder.WriteString(r.Content)
 }
 
-func (c *ChildList) Render() string {
-	builder := &strings.Builder{}
+func (c *ChildList) Render(builder *strings.Builder) {
 	for _, child := range c.Children {
-		builder.WriteString(child.Render())
+		child.Render(builder)
 	}
-	str := builder.String()
-	return str
 }
 
-func (m *AttributeMap) Render() string {
-	builder := &strings.Builder{}
+func (m *AttributeMap) Render(builder *strings.Builder) {
 	m2 := m.ToMap()
 
 	for k, v := range m2 {
-		builder.WriteString(NewAttribute(k, v).Render())
+		NewAttribute(k, v).Render(builder)
+	}
 }
 
-	str := builder.String()
-	return str
-}
-
-func (l *LifeCycle) Render() string {
+func (l *LifeCycle) Render(builder *strings.Builder) {
 	m := make(map[string]string)
 
 	for event, commands := range l.handlers {
@@ -114,8 +102,7 @@ func (l *LifeCycle) Render() string {
 		children = append(children, Attribute(event, js))
 	}
 
-	result := Children(children...).Render()
-	return result
+	Children(children...).Render(builder)
 }
 
 func (m *AttributeMap) ToMap() map[string]string {

framework/h/tag.go

@@ -14,7 +14,7 @@ type Element struct {
 	children   []Ren
 }
 
-func (node *Element) AppendChild(child Ren) Ren {
+func (node *Element) AppendChild(child Ren) *Element {
 	node.children = append(node.children, child)
 	return node
 }
@@ -363,7 +363,7 @@ func List[T any](items []T, mapper func(item T, index int) *Element) *Element {
 	return node
 }
 
-func Fragment(children ...Ren) Ren {
+func Fragment(children ...Ren) *Element {
 	return &Element{
 		tag:      "",
 		children: children,
@@ -541,11 +541,11 @@ func NewSwap(selector string, content *Element) SwapArg {
 	}
 }
 
-func OobSwap(ctx *RequestContext, content *Element) Ren {
+func OobSwap(ctx *RequestContext, content *Element) *Element {
 	return OobSwapWithSelector(ctx, "", content)
 }
 
-func OobSwapWithSelector(ctx *RequestContext, selector string, content *Element) Ren {
+func OobSwapWithSelector(ctx *RequestContext, selector string, content *Element) *Element {
 	if ctx == nil || ctx.Get("HX-Request") == "" {
 		return Empty()
 	}

framework/h/util.go

@@ -4,10 +4,11 @@ import (
 	"encoding/json"
 	"github.com/labstack/echo/v4"
 	"net/url"
+	"strings"
 )
 
 type Ren interface {
-	Render() string
+	Render(builder *strings.Builder)
 }
 
 func Ternary[T any](value bool, a T, b T) T {

todo-list/partials/task/task.go

@@ -215,7 +215,8 @@ func UpdateName(ctx *h.RequestContext) *h.Partial {
 		return h.NewPartial(h.Div(h.Text("failed to update")))
 	}
 
-	return h.NewPartial(h.OobSwap(ctx, Task(task, false)))
+	return h.NewPartial(
+		h.OobSwap(ctx, Task(task, false)))
 }
 
 func EditNameForm(ctx *h.RequestContext) *h.Partial {