Fix deleted Content-Length header bug.

middleware/gzip/gzip.go

@@ -3,6 +3,7 @@
 package gzip
 
 import (
+	"bytes"
 	"compress/gzip"
 	"fmt"
 	"io"
@@ -47,9 +48,13 @@ outer:
 		// Delete this header so gzipping is not repeated later in the chain
 		r.Header.Del("Accept-Encoding")
 
-		w.Header().Set("Content-Encoding", "gzip")
-		w.Header().Set("Vary", "Accept-Encoding")
-		gzipWriter, err := newWriter(c, w)
+		// gzipWriter modifies underlying writer at init,
+		// use a buffer instead to leave ResponseWriter in
+		// original form.
+		var buf = &bytes.Buffer{}
+		defer buf.Reset()
+
+		gzipWriter, err := newWriter(c, buf)
 		if err != nil {
 			// should not happen
 			return http.StatusInternalServerError, err
@@ -60,6 +65,8 @@ outer:
 		var rw http.ResponseWriter
 		// if no response filter is used
 		if len(c.ResponseFilters) == 0 {
+			// replace buffer with ResponseWriter
+			gzipWriter.Reset(w)
 			rw = gz
 		} else {
 			// wrap gzip writer with ResponseFilterWriter
@@ -88,7 +95,7 @@ outer:
 // newWriter create a new Gzip Writer based on the compression level.
 // If the level is valid (i.e. between 1 and 9), it uses the level.
 // Otherwise, it uses default compression level.
-func newWriter(c Config, w http.ResponseWriter) (*gzip.Writer, error) {
+func newWriter(c Config, w io.Writer) (*gzip.Writer, error) {
 	if c.Level >= gzip.BestSpeed && c.Level <= gzip.BestCompression {
 		return gzip.NewWriterLevel(w, c.Level)
 	}
@@ -108,6 +115,8 @@ type gzipResponseWriter struct {
 // be wrong because it doesn't know it's being gzipped.
 func (w gzipResponseWriter) WriteHeader(code int) {
 	w.Header().Del("Content-Length")
+	w.Header().Set("Content-Encoding", "gzip")
+	w.Header().Set("Vary", "Accept-Encoding")
 	w.ResponseWriter.WriteHeader(code)
 }
 

middleware/gzip/gzip_test.go

@@ -80,6 +80,8 @@ func TestGzipHandler(t *testing.T) {
 
 func nextFunc(shouldGzip bool) middleware.Handler {
 	return middleware.HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
+		w.WriteHeader(200)
+		w.Write([]byte("test"))
 		if shouldGzip {
 			if r.Header.Get("Accept-Encoding") != "" {
 				return 0, fmt.Errorf("Accept-Encoding header not expected")

middleware/gzip/response_filter.go

@@ -1,6 +1,7 @@
 package gzip
 
 import (
+	"compress/gzip"
 	"net/http"
 	"strconv"
 )
@@ -29,7 +30,6 @@ func (l LengthFilter) ShouldCompress(w http.ResponseWriter) bool {
 // uncompressed data otherwise.
 type ResponseFilterWriter struct {
 	filters        []ResponseFilter
-	validated      bool
 	shouldCompress bool
 	gzipResponseWriter
 }
@@ -40,21 +40,33 @@ func NewResponseFilterWriter(filters []ResponseFilter, gz gzipResponseWriter) *R
 }
 
 // Write wraps underlying Write method and compresses if filters
-// are satisfied
-func (r *ResponseFilterWriter) Write(b []byte) (int, error) {
-	// One time validation to determine if compression should
-	// be used or not.
-	if !r.validated {
-		r.shouldCompress = true
-		for _, filter := range r.filters {
-			if !filter.ShouldCompress(r) {
-				r.shouldCompress = false
-				break
-			}
+// are satisfied.
+func (r *ResponseFilterWriter) WriteHeader(code int) {
+	// Determine if compression should be used or not.
+	r.shouldCompress = true
+	for _, filter := range r.filters {
+		if !filter.ShouldCompress(r) {
+			r.shouldCompress = false
+			break
 		}
-		r.validated = true
 	}
 
+	if r.shouldCompress {
+		// replace buffer with ResponseWriter
+		if gzWriter, ok := r.gzipResponseWriter.Writer.(*gzip.Writer); ok {
+			gzWriter.Reset(r.ResponseWriter)
+		}
+		// use gzip WriteHeader to include and delete
+		// necessary headers
+		r.gzipResponseWriter.WriteHeader(code)
+	} else {
+		r.ResponseWriter.WriteHeader(code)
+	}
+}
+
+// Write wraps underlying Write method and compresses if filters
+// are satisfied
+func (r *ResponseFilterWriter) Write(b []byte) (int, error) {
 	if r.shouldCompress {
 		return r.gzipResponseWriter.Write(b)
 	}

middleware/gzip/response_filter_test.go

@@ -3,8 +3,11 @@ package gzip
 import (
 	"compress/gzip"
 	"fmt"
+	"net/http"
 	"net/http/httptest"
 	"testing"
+
+	"github.com/mholt/caddy/middleware"
 )
 
 func TestLengthFilter(t *testing.T) {
@@ -30,7 +33,8 @@ func TestLengthFilter(t *testing.T) {
 		for j, filter := range filters {
 			r := httptest.NewRecorder()
 			r.Header().Set("Content-Length", fmt.Sprint(ts.length))
-			if filter.ShouldCompress(r) != ts.shouldCompress[j] {
+			wWriter := NewResponseFilterWriter([]ResponseFilter{filter}, gzipResponseWriter{gzip.NewWriter(r), r})
+			if filter.ShouldCompress(wWriter) != ts.shouldCompress[j] {
 				t.Errorf("Test %v: Expected %v found %v", i, ts.shouldCompress[j], filter.ShouldCompress(r))
 			}
 		}
@@ -47,16 +51,32 @@ func TestResponseFilterWriter(t *testing.T) {
 		{"Hello \t\t\nfrom gzip", true},
 		{"Hello gzip\n", false},
 	}
+
 	filters := []ResponseFilter{
 		LengthFilter(15),
 	}
+
+	server := Gzip{Configs: []Config{
+		{ResponseFilters: filters},
+	}}
+
 	for i, ts := range tests {
+		server.Next = middleware.HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
+			w.Header().Set("Content-Length", fmt.Sprint(len(ts.body)))
+			w.WriteHeader(200)
+			w.Write([]byte(ts.body))
+			return 200, nil
+		})
+
+		r := urlRequest("/")
+		r.Header.Set("Accept-Encoding", "gzip")
+
 		w := httptest.NewRecorder()
-		w.Header().Set("Content-Length", fmt.Sprint(len(ts.body)))
-		gz := gzipResponseWriter{gzip.NewWriter(w), w}
-		rw := NewResponseFilterWriter(filters, gz)
-		rw.Write([]byte(ts.body))
+
+		server.ServeHTTP(w, r)
+
 		resp := w.Body.String()
+
 		if !ts.shouldCompress {
 			if resp != ts.body {
 				t.Errorf("Test %v: No compression expected, found %v", i, resp)