Further performance optimization

static_test.go

@@ -1,10 +1,14 @@
 package main
 
 import (
+	"bytes"
+	"compress/gzip"
+	"io"
 	"io/fs"
 	"net/http"
 	"net/http/httptest"
 	"regexp"
+	"strings"
 	"testing"
 )
 
@@ -56,3 +60,52 @@ func TestServeStaticCaching(t *testing.T) {
 		t.Errorf("font: %q", w.Header().Get("Cache-Control"))
 	}
 }
+
+func TestServeStaticGzip(t *testing.T) {
+	h := serveStatic()
+	get := func(url, acceptEncoding, ifNoneMatch string) *httptest.ResponseRecorder {
+		r := httptest.NewRequest(http.MethodGet, url, nil)
+		if acceptEncoding != "" {
+			r.Header.Set("Accept-Encoding", acceptEncoding)
+		}
+		if ifNoneMatch != "" {
+			r.Header.Set("If-None-Match", ifNoneMatch)
+		}
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, r)
+		return w
+	}
+	want, _ := assets.ReadFile("assets/style.css")
+
+	w := get("/_/style.css", "gzip, deflate, br", "")
+	if w.Code != 200 || w.Header().Get("Content-Encoding") != "gzip" || w.Header().Get("Vary") != "Accept-Encoding" {
+		t.Fatalf("gzip: %d %q %q", w.Code, w.Header().Get("Content-Encoding"), w.Header().Get("Vary"))
+	}
+	if ct := w.Header().Get("Content-Type"); !strings.HasPrefix(ct, "text/css") {
+		t.Errorf("content-type: %q", ct)
+	}
+	zr, err := gzip.NewReader(w.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, _ := io.ReadAll(zr)
+	if !bytes.Equal(got, want) {
+		t.Errorf("gzip body does not decompress to style.css")
+	}
+
+	etag := w.Header().Get("ETag")
+	if w := get("/_/style.css", "gzip", etag); w.Code != http.StatusNotModified {
+		t.Errorf("gzip revalidate: got %d, want 304", w.Code)
+	}
+
+	for _, ae := range []string{"", "identity", "gzip;q=0"} {
+		w := get("/_/style.css", ae, "")
+		if w.Header().Get("Content-Encoding") != "" || !bytes.Equal(w.Body.Bytes(), want) {
+			t.Errorf("Accept-Encoding %q: got encoding %q", ae, w.Header().Get("Content-Encoding"))
+		}
+	}
+
+	if w := get("/_/fonts/IosevkaSlab.woff2", "gzip", ""); w.Header().Get("Content-Encoding") != "" {
+		t.Errorf("font should not be re-compressed")
+	}
+}