lib/assets: Allow assets to remain uncompressed (#6661)

script/genassets.go

@@ -15,6 +15,7 @@ import (
 	"fmt"
 	"go/format"
 	"io"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -27,20 +28,35 @@ var tpl = template.Must(template.New("assets").Parse(`// Code generated by genas
 
 package auto
 
-const Generated int64 = {{.Generated}}
+import (
+	"time"
+
+	"github.com/syncthing/syncthing/lib/assets"
+)
+
+func Assets() map[string]assets.Asset {
+	var ret = make(map[string]assets.Asset, {{.Assets | len}})
+	t := time.Unix({{.Generated}}, 0)
 
-func Assets() map[string]string {
-	var assets = make(map[string]string, {{.Assets | len}})
 {{range $asset := .Assets}}
-	assets["{{$asset.Name}}"] = {{$asset.Data}}{{end}}
-	return assets
+	ret["{{$asset.Name}}"] = assets.Asset{
+		Content:  {{$asset.Data}},
+		Gzipped:  {{$asset.Gzipped}},
+		Length:   {{$asset.Length}},
+		Filename: {{$asset.Name | printf "%q"}},
+		Modified: t,
+	}
+{{end}}
+	return ret
 }
 
 `))
 
 type asset struct {
-	Name string
-	Data string
+	Name    string
+	Data    string
+	Length  int
+	Gzipped bool
 }
 
 var assets []asset
@@ -57,22 +73,32 @@ func walkerFor(basePath string) filepath.WalkFunc {
 		}
 
 		if info.Mode().IsRegular() {
-			fd, err := os.Open(name)
+			data, err := ioutil.ReadFile(name)
 			if err != nil {
 				return err
 			}
+			length := len(data)
 
 			var buf bytes.Buffer
-			gw := gzip.NewWriter(&buf)
-			io.Copy(gw, fd)
-			fd.Close()
-			gw.Flush()
+			gw, _ := gzip.NewWriterLevel(&buf, gzip.BestCompression)
+			gw.Write(data)
 			gw.Close()
 
+			// Only replace asset by gzipped version if it is smaller.
+			// In practice, this means HTML, CSS, SVG etc. get compressed,
+			// while PNG and WOFF files are left uncompressed.
+			// lib/assets detects gzip and sets headers/decompresses.
+			gzipped := buf.Len() < len(data)
+			if gzipped {
+				data = buf.Bytes()
+			}
+
 			name, _ = filepath.Rel(basePath, name)
 			assets = append(assets, asset{
-				Name: filepath.ToSlash(name),
-				Data: fmt.Sprintf("%q", buf.String()),
+				Name:    filepath.ToSlash(name),
+				Data:    fmt.Sprintf("%q", string(data)),
+				Length:  length,
+				Gzipped: gzipped,
 			})
 		}