Fix caching on JSON body read

httpcache.go

@@ -533,7 +533,7 @@ type cachingReadCloser struct {
 func (r *cachingReadCloser) Read(p []byte) (n int, err error) {
 	n, err = r.R.Read(p)
 	r.buf.Write(p[:n])
-	if err == io.EOF {
+	if err == io.EOF || n < len(p) {
 		r.OnEOF(bytes.NewReader(r.buf.Bytes()))
 	}
 	return n, err

httpcache_test.go

@@ -2,6 +2,7 @@ package httpcache
 
 import (
 	"bytes"
+	"encoding/json"
 	"errors"
 	"flag"
 	"io"
@@ -158,6 +159,15 @@ func setup() {
 			}
 		}
 	}))
+
+	mux.HandleFunc("/json", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "max-age=3600")
+		w.Header().Set("Content-Type", "application/json")
+		// This will force using bufio.Read() instead of chunkedReader.Read()
+		// to miss the EOF.
+		w.Header().Set("Transfer-encoding", "identity")
+		json.NewEncoder(w).Encode(map[string]string{"k": "v"})
+	}))
 }
 
 func teardown() {
@@ -398,6 +408,43 @@ func TestCacheOnlyIfBodyRead(t *testing.T) {
 	}
 }
 
+func TestCacheOnJsonBodyRead(t *testing.T) {
+	resetTest()
+	{
+		req, err := http.NewRequest("GET", s.server.URL+"/json", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := s.client.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer resp.Body.Close()
+		var r json.RawMessage
+		err = json.NewDecoder(resp.Body).Decode(&r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if resp.Header.Get(XFromCache) != "" {
+			t.Fatalf("XFromCache header isn't blank")
+		}
+	}
+	{
+		req, err := http.NewRequest("GET", s.server.URL+"/json", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := s.client.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer resp.Body.Close()
+		if resp.Header.Get(XFromCache) != "1" {
+			t.Fatalf("XFromCache header isn't set")
+		}
+	}
+}
+
 func TestOnlyReadBodyOnDemand(t *testing.T) {
 	resetTest()