Add render cache for SVG icons

Cache the final rendered template.HTML output for SVG icons that use
non-default size or class parameters using sync.Map. Icons rendered with
default parameters bypass the cache and use a direct read-only map lookup.

Co-Authored-By: Claude (Opus 4.6) <noreply@anthropic.com>

Author: silverwind

modules/svg/svg.go

@@ -8,15 +8,33 @@ import (
 	"html/template"
 	"path"
 	"strings"
+	"sync"
+	"sync/atomic"
 
 	gitea_html "code.gitea.io/gitea/modules/htmlutil"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/public"
 )
 
-var svgIcons map[string]string
+type svgCacheKey struct {
+	icon  string
+	size  int
+	class string
+}
+
+var (
+	svgIcons                 map[string]string
+	svgRenderedHTMLCache     sync.Map
+	svgRenderedHTMLCacheSize atomic.Int32
+)
 
 const defaultSize = 16
+const cacheLimit = 10000
+
+func clearSVGRenderCache() {
+	svgRenderedHTMLCache.Clear()
+	svgRenderedHTMLCacheSize.Store(0)
+}
 
 // Init discovers SVG icons and populates the `svgIcons` variable
 func Init() error {
@@ -26,6 +44,7 @@ func Init() error {
 		return err
 	}
 
+	clearSVGRenderCache()
 	svgIcons = make(map[string]string, len(files))
 	for _, file := range files {
 		if path.Ext(file) != ".svg" {
@@ -45,9 +64,12 @@ func MockIcon(icon string) func() {
 	if svgIcons == nil {
 		svgIcons = make(map[string]string)
 	}
+	clearSVGRenderCache()
 	orig, exist := svgIcons[icon]
 	svgIcons[icon] = fmt.Sprintf(`<svg class="svg %s" width="%d" height="%d"></svg>`, icon, defaultSize, defaultSize)
 	return func() {
+		svgRenderedHTMLCache.Clear()
+		svgRenderedHTMLCacheSize.Store(0)
 		if exist {
 			svgIcons[icon] = orig
 		} else {
@@ -63,6 +85,13 @@ func RenderHTML(icon string, others ...any) template.HTML {
 	}
 	size, class := gitea_html.ParseSizeAndClass(defaultSize, "", others...)
 	if svgStr, ok := svgIcons[icon]; ok {
+		if size == defaultSize && class == "" {
+			return template.HTML(svgStr)
+		}
+		cacheKey := svgCacheKey{icon, size, class}
+		if v, ok := svgRenderedHTMLCache.Load(cacheKey); ok {
+			return v.(template.HTML)
+		}
 		// the code is somewhat hacky, but it just works, because the SVG contents are all normalized
 		if size != defaultSize {
 			svgStr = strings.Replace(svgStr, fmt.Sprintf(`width="%d"`, defaultSize), fmt.Sprintf(`width="%d"`, size), 1)
@@ -71,7 +100,13 @@ func RenderHTML(icon string, others ...any) template.HTML {
 		if class != "" {
 			svgStr = strings.Replace(svgStr, `class="`, fmt.Sprintf(`class="%s `, class), 1)
 		}
-		return template.HTML(svgStr)
+		result := template.HTML(svgStr)
+		if svgRenderedHTMLCacheSize.Load() >= cacheLimit {
+			clearSVGRenderCache()
+		}
+		svgRenderedHTMLCache.Store(cacheKey, result)
+		svgRenderedHTMLCacheSize.Add(1)
+		return result
 	}
 	// during test (or something wrong happens), there is no SVG loaded, so use a dummy span to tell that the icon is missing
 	return template.HTML(fmt.Sprintf("<span>%s(%d/%s)</span>", template.HTMLEscapeString(icon), size, template.HTMLEscapeString(class)))

modules/svg/svg_test.go

@@ -0,0 +1,68 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package svg
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRenderHTMLCache(t *testing.T) {
+	svgIcons = map[string]string{
+		"test-icon": `<svg class="svg test-icon" width="16" height="16"><path/></svg>`,
+	}
+	svgRenderedHTMLCache.Clear()
+
+	// default size and no class: fast path, no cache entry
+	result := RenderHTML("test-icon")
+	assert.Equal(t, `<svg class="svg test-icon" width="16" height="16"><path/></svg>`, string(result))
+	_, cached := svgRenderedHTMLCache.Load(svgCacheKey{"test-icon", 16, ""})
+	assert.False(t, cached, "default params should not create a cache entry")
+
+	// custom size: should cache
+	result = RenderHTML("test-icon", 24)
+	assert.Contains(t, string(result), `width="24"`)
+	assert.Contains(t, string(result), `height="24"`)
+	_, cached = svgRenderedHTMLCache.Load(svgCacheKey{"test-icon", 24, ""})
+	assert.True(t, cached, "custom size should create a cache entry")
+
+	// custom class: should cache
+	result = RenderHTML("test-icon", 16, "extra")
+	assert.Contains(t, string(result), `class="extra svg test-icon"`)
+	_, cached = svgRenderedHTMLCache.Load(svgCacheKey{"test-icon", 16, "extra"})
+	assert.True(t, cached, "custom class should create a cache entry")
+
+	// cache hit returns same result
+	result2 := RenderHTML("test-icon", 24)
+	assert.Equal(t, result2, RenderHTML("test-icon", 24))
+
+	// missing icon returns dummy span
+	result = RenderHTML("nonexistent", 16, "cls")
+	assert.Contains(t, string(result), "<span>")
+	assert.Contains(t, string(result), "nonexistent")
+}
+
+func TestMockIconClearsCache(t *testing.T) {
+	svgIcons = map[string]string{
+		"mock-icon": `<svg class="svg mock-icon" width="16" height="16"><path/></svg>`,
+	}
+	svgRenderedHTMLCache.Clear()
+
+	// populate cache
+	RenderHTML("mock-icon", 24)
+	_, cached := svgRenderedHTMLCache.Load(svgCacheKey{"mock-icon", 24, ""})
+	assert.True(t, cached)
+
+	// MockIcon should clear cache
+	restore := MockIcon("mock-icon")
+	_, cached = svgRenderedHTMLCache.Load(svgCacheKey{"mock-icon", 24, ""})
+	assert.False(t, cached, "MockIcon should clear cache")
+
+	// restore should also clear cache
+	RenderHTML("mock-icon", 24)
+	restore()
+	_, cached = svgRenderedHTMLCache.Load(svgCacheKey{"mock-icon", 24, ""})
+	assert.False(t, cached, "restore should clear cache")
+}