pretty-print json in http requests/responses

helper/logging/transport.go

@@ -1,9 +1,12 @@
 package logging
 
 import (
+	"bytes"
+	"encoding/json"
 	"log"
 	"net/http"
 	"net/http/httputil"
+	"strings"
 )
 
 type transport struct {
@@ -15,7 +18,7 @@ func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	if IsDebugOrHigher() {
 		reqData, err := httputil.DumpRequestOut(req, true)
 		if err == nil {
-			log.Printf("[DEBUG] "+logReqMsg, t.name, string(reqData))
+			log.Printf("[DEBUG] "+logReqMsg, t.name, prettyPrintJsonLines(reqData))
 		} else {
 			log.Printf("[ERROR] %s API Request error: %#v", t.name, err)
 		}
@@ -29,7 +32,7 @@ func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	if IsDebugOrHigher() {
 		respData, err := httputil.DumpResponse(resp, true)
 		if err == nil {
-			log.Printf("[DEBUG] "+logRespMsg, t.name, string(respData))
+			log.Printf("[DEBUG] "+logRespMsg, t.name, prettyPrintJsonLines(respData))
 		} else {
 			log.Printf("[ERROR] %s API Response error: %#v", t.name, err)
 		}
@@ -42,6 +45,20 @@ func NewTransport(name string, t http.RoundTripper) *transport {
 	return &transport{name, t}
 }
 
+// prettyPrintJsonLines iterates through a []byte line-by-line,
+// transforming any lines that are complete json into pretty-printed json.
+func prettyPrintJsonLines(b []byte) string {
+	parts := strings.Split(string(b), "\n")
+	for i, p := range parts {
+		if b := []byte(p); json.Valid(b) {
+			var out bytes.Buffer
+			json.Indent(&out, b, "", " ")
+			parts[i] = out.String()
+		}
+	}
+	return strings.Join(parts, "\n")
+}
+
 const logReqMsg = `%s API Request Details:
 ---[ REQUEST ]---------------------------------------
 %s