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

cmd/strelaypoolsrv/main.go

@@ -268,17 +268,13 @@ func handleAssets(w http.ResponseWriter, r *http.Request) {
 		path = "index.html"
 	}
 
-	content, ok := auto.Assets()[path]
+	as, ok := auto.Assets()[path]
 	if !ok {
 		w.WriteHeader(http.StatusNotFound)
 		return
 	}
 
-	assets.Serve(w, r, assets.Asset{
-		ContentGz: content,
-		Filename:  path,
-		Modified:  time.Unix(auto.Generated, 0).UTC(),
-	})
+	assets.Serve(w, r, as)
 }
 
 func handleRequest(w http.ResponseWriter, r *http.Request) {

lib/api/api.go

@@ -1267,7 +1267,7 @@ func (s *service) getEventSub(mask events.EventType) events.BufferedSubscription
 
 func (s *service) getSystemUpgrade(w http.ResponseWriter, r *http.Request) {
 	if s.noUpgrade {
-		http.Error(w, upgrade.ErrUpgradeUnsupported.Error(), 500)
+		http.Error(w, upgrade.ErrUpgradeUnsupported.Error(), http.StatusServiceUnavailable)
 		return
 	}
 	opts := s.cfg.Options()

lib/api/api_statics.go

@@ -24,7 +24,7 @@ const themePrefix = "theme-assets/"
 
 type staticsServer struct {
 	assetDir        string
-	assets          map[string]string
+	assets          map[string]assets.Asset
 	availableThemes []string
 
 	mut             sync.RWMutex
@@ -118,7 +118,7 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Check for a compiled in asset for the current theme.
-	bs, ok := s.assets[theme+"/"+file]
+	as, ok := s.assets[theme+"/"+file]
 	if !ok {
 		// Check for an overridden default asset.
 		if s.assetDir != "" {
@@ -134,18 +134,15 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 		}
 
 		// Check for a compiled in default asset.
-		bs, ok = s.assets[config.DefaultTheme+"/"+file]
+		as, ok = s.assets[config.DefaultTheme+"/"+file]
 		if !ok {
 			http.NotFound(w, r)
 			return
 		}
 	}
 
-	assets.Serve(w, r, assets.Asset{
-		ContentGz: bs,
-		Filename:  file,
-		Modified:  modificationTime,
-	})
+	as.Modified = modificationTime
+	assets.Serve(w, r, as)
 }
 
 func (s *staticsServer) serveThemes(w http.ResponseWriter, r *http.Request) {

lib/api/api_test.go

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/d4l3k/messagediff"
+	"github.com/syncthing/syncthing/lib/assets"
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/fs"
@@ -152,19 +153,25 @@ func TestAssetsDir(t *testing.T) {
 	gw := gzip.NewWriter(buf)
 	gw.Write([]byte("default"))
 	gw.Close()
-	def := buf.String()
+	def := assets.Asset{
+		Content: buf.String(),
+		Gzipped: true,
+	}
 
 	buf = new(bytes.Buffer)
 	gw = gzip.NewWriter(buf)
 	gw.Write([]byte("foo"))
 	gw.Close()
-	foo := buf.String()
+	foo := assets.Asset{
+		Content: buf.String(),
+		Gzipped: true,
+	}
 
 	e := &staticsServer{
 		theme:    "foo",
 		mut:      sync.NewRWMutex(),
 		assetDir: "testdata",
-		assets: map[string]string{
+		assets: map[string]assets.Asset{
 			"foo/a":     foo, // overridden in foo/a
 			"foo/b":     foo,
 			"default/a": def, // overridden in default/a (but foo/a takes precedence)

lib/api/auto/auto_test.go

@@ -22,9 +22,12 @@ func TestAssets(t *testing.T) {
 	if !ok {
 		t.Fatal("No index.html in compiled in assets")
 	}
+	if !idx.Gzipped {
+		t.Fatal("default/index.html should be compressed")
+	}
 
 	var gr *gzip.Reader
-	gr, _ = gzip.NewReader(strings.NewReader(idx))
+	gr, _ = gzip.NewReader(strings.NewReader(idx.Content))
 	html, _ := ioutil.ReadAll(gr)
 
 	if !bytes.Contains(html, []byte("<html")) {

lib/assets/assets.go

@@ -22,11 +22,13 @@ import (
 	"time"
 )
 
-// Asset is the type of arguments to Serve.
+// An Asset is an embedded file to be served over HTTP.
 type Asset struct {
-	ContentGz string    // gzipped contents of asset.
-	Filename  string    // Original filename, determines Content-Type.
-	Modified  time.Time // Determines ETag and Last-Modified.
+	Content  string // Contents of asset, possibly gzipped.
+	Gzipped  bool
+	Length   int       // Length of (decompressed) Content.
+	Filename string    // Original filename, determines Content-Type.
+	Modified time.Time // Determines ETag and Last-Modified.
 }
 
 // Serve writes a gzipped asset to w.
@@ -53,14 +55,19 @@ func Serve(w http.ResponseWriter, r *http.Request, asset Asset) {
 		return
 	}
 
-	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+	switch {
+	case !asset.Gzipped:
+		header.Set("Content-Length", strconv.Itoa(len(asset.Content)))
+		io.WriteString(w, asset.Content)
+	case strings.Contains(r.Header.Get("Accept-Encoding"), "gzip"):
 		header.Set("Content-Encoding", "gzip")
-		header.Set("Content-Length", strconv.Itoa(len(asset.ContentGz)))
-		io.WriteString(w, asset.ContentGz)
-	} else {
+		header.Set("Content-Length", strconv.Itoa(len(asset.Content)))
+		io.WriteString(w, asset.Content)
+	default:
+		header.Set("Content-Length", strconv.Itoa(asset.Length))
 		// gunzip for browsers that don't want gzip.
 		var gr *gzip.Reader
-		gr, _ = gzip.NewReader(strings.NewReader(asset.ContentGz))
+		gr, _ = gzip.NewReader(strings.NewReader(asset.Content))
 		io.Copy(w, gr)
 		gr.Close()
 	}

lib/assets/assets_test.go

@@ -13,6 +13,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -38,15 +39,23 @@ func decompress(p []byte) (out []byte) {
 	return out
 }
 
-func TestServe(t *testing.T) {
-	indexHTML := `<html>Hello, world!</html>`
-	indexGz := compress(indexHTML)
+func TestServe(t *testing.T)     { testServe(t, false) }
+func TestServeGzip(t *testing.T) { testServe(t, true) }
+
+func testServe(t *testing.T, gzip bool) {
+	const indexHTML = `<html>Hello, world!</html>`
+	content := indexHTML
+	if gzip {
+		content = compress(indexHTML)
+	}
 
 	handler := func(w http.ResponseWriter, r *http.Request) {
 		Serve(w, r, Asset{
-			ContentGz: indexGz,
-			Filename:  r.URL.Path[1:],
-			Modified:  time.Unix(0, 0),
+			Content:  content,
+			Gzipped:  gzip,
+			Length:   len(indexHTML),
+			Filename: r.URL.Path[1:],
+			Modified: time.Unix(0, 0),
 		})
 	}
 
@@ -73,7 +82,17 @@ func TestServe(t *testing.T) {
 		}
 
 		body, _ := ioutil.ReadAll(res.Body)
-		if acceptGzip {
+
+		// Content-Length is the number of bytes in the encoded (compressed) body
+		// (https://stackoverflow.com/a/3819303).
+		n, err := strconv.Atoi(res.Header.Get("Content-Length"))
+		if err != nil {
+			t.Errorf("malformed Content-Length %q", res.Header.Get("Content-Length"))
+		} else if n != len(body) {
+			t.Errorf("wrong Content-Length %d, should be %d", n, len(body))
+		}
+
+		if gzip && acceptGzip {
 			body = decompress(body)
 		}
 		if string(body) != indexHTML {

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,
 			})
 		}