Fix deferred header ops

modules/caddyhttp/headers/headers.go

@@ -17,16 +17,16 @@ func init() {
 
 // Headers is a middleware which can mutate HTTP headers.
 type Headers struct {
-	Request  HeaderOps
-	Response RespHeaderOps
+	Request  HeaderOps     `json:"request"`
+	Response RespHeaderOps `json:"response"`
 }
 
 // HeaderOps defines some operations to
 // perform on HTTP headers.
 type HeaderOps struct {
-	Add    http.Header
-	Set    http.Header
-	Delete []string
+	Add    http.Header `json:"add"`
+	Set    http.Header `json:"set"`
+	Delete []string    `json:"delete"`
 }
 
 // RespHeaderOps is like HeaderOps, but
@@ -68,9 +68,21 @@ func apply(ops HeaderOps, hdr http.Header) {
 type responseWriterWrapper struct {
 	*caddyhttp.ResponseWriterWrapper
 	headerOps   HeaderOps
+	wroteHeader bool
+}
+
+func (rww *responseWriterWrapper) Write(d []byte) (int, error) {
+	if !rww.wroteHeader {
+		rww.WriteHeader(http.StatusOK)
+	}
+	return rww.ResponseWriterWrapper.Write(d)
 }
 
 func (rww *responseWriterWrapper) WriteHeader(status int) {
+	if rww.wroteHeader {
+		return
+	}
+	rww.wroteHeader = true
 	apply(rww.headerOps, rww.ResponseWriterWrapper.Header())
 	rww.ResponseWriterWrapper.WriteHeader(status)
 }

modules/caddyhttp/staticresp.go

@@ -17,7 +17,7 @@ func init() {
 
 // Static implements a simple responder for static responses.
 type Static struct {
-	StatusCode    int         `json:"status_code"`
+	StatusCode    int         `json:"status_code"` // TODO: should we turn this into a string so that only one field is needed? (string allows replacements)
 	StatusCodeStr string      `json:"status_code_str"`
 	Headers       http.Header `json:"headers"`
 	Body          string      `json:"body"`
@@ -30,7 +30,7 @@ func (s Static) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
 	// close the connection after responding
 	r.Close = s.Close
 
-	// set all headers, with replacements
+	// set all headers
 	for field, vals := range s.Headers {
 		field = repl.ReplaceAll(field, "")
 		for i := range vals {
@@ -39,7 +39,7 @@ func (s Static) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
 		w.Header()[field] = vals
 	}
 
-	// write the headers with a status code
+	// get the status code
 	statusCode := s.StatusCode
 	if statusCode == 0 && s.StatusCodeStr != "" {
 		intVal, err := strconv.Atoi(repl.ReplaceAll(s.StatusCodeStr, ""))
@@ -50,9 +50,11 @@ func (s Static) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
 	if statusCode == 0 {
 		statusCode = http.StatusOK
 	}
+
+	// write headers
 	w.WriteHeader(statusCode)
 
-	// write the response body, with replacements
+	// write response body
 	if s.Body != "" {
 		fmt.Fprint(w, repl.ReplaceAll(s.Body, ""))
 	}