Support pretty json printing

Signed-off-by: Han Verstraete (OpenFaaS Ltd) <han@openfaas.com>

printer/handler.go

@@ -1,20 +1,53 @@
 package function
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
+	"os"
+	"strconv"
 )
 
+func formatJSON(data []byte) ([]byte, error) {
+	var out bytes.Buffer
+
+	if err := json.Indent(&out, data, "", "    "); err != nil {
+		return data, err
+	}
+
+	return out.Bytes(), nil
+}
+
+func printRaw() bool {
+	val := os.Getenv("RAW")
+	raw, err := strconv.ParseBool(val)
+	if err != nil {
+		return false
+	}
+	return raw
+}
+
 func Handle(w http.ResponseWriter, r *http.Request) {
 	var input []byte
 
+	contentType := r.Header.Get("content-type")
 	if r.Body != nil {
 		defer r.Body.Close()
 
 		body, _ := io.ReadAll(r.Body)
 
-		input = body
+		if !printRaw() && contentType == "application/json" {
+			var err error
+			input, err = formatJSON(body)
+			if err != nil {
+				http.Error(w, fmt.Sprintf("failed to format JSON body: %s", err), http.StatusInternalServerError)
+				return
+			}
+		} else {
+			input = body
+		}
 	}
 
 	for k, v := range r.Header {