httpserver: support more file types of custom error page (#3196)

Co-authored-by: Aapeli.Smith <aapelismith@users.noreply.github.com>

caddyhttp/errors/errors.go

@@ -18,8 +18,10 @@ package errors
 import (
 	"fmt"
 	"io"
+	"mime"
 	"net/http"
 	"os"
+	"path/filepath"
 	"runtime"
 	"strings"
 
@@ -83,9 +85,13 @@ func (h ErrorHandler) errorPage(w http.ResponseWriter, r *http.Request, code int
 			return
 		}
 		defer errorPage.Close()
-
+		// Get content type by extension
+		contentType := mime.TypeByExtension(filepath.Ext(pagePath))
+		if contentType == "" {
+			contentType = "text/html; charset=utf-8"
+		}
 		// Copy the page body into the response
-		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.Header().Set("Content-Type", contentType)
 		w.WriteHeader(code)
 		_, err = io.Copy(w, errorPage)
 

caddyhttp/errors/errors_test.go

@@ -167,6 +167,7 @@ func TestVisibleErrorWithPanic(t *testing.T) {
 func TestGenericErrorPage(t *testing.T) {
 	// create temporary generic error page
 	const genericErrorContent = "This is a generic error page"
+	const badRequestErrorJSONContent = `{"message":"This is a error json message"}`
 
 	genericErrorPagePath, err := createErrorPageFile("generic_error_test.html", genericErrorContent)
 	if err != nil {
@@ -183,11 +184,18 @@ func TestGenericErrorPage(t *testing.T) {
 	}
 	defer os.Remove(notFoundErrorPagePath)
 
+	badRequestErrorJSONPath, err := createErrorPageFile("not_found.json", badRequestErrorJSONContent)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(badRequestErrorJSONPath)
+
 	buf := bytes.Buffer{}
 	em := ErrorHandler{
 		GenericErrorPage: genericErrorPagePath,
 		ErrorPages: map[int]string{
 			http.StatusNotFound: notFoundErrorPagePath,
+			http.StatusBadRequest:badRequestErrorJSONPath,
 		},
 		Log: httpserver.NewTestLogger(&buf),
 	}
@@ -198,6 +206,7 @@ func TestGenericErrorPage(t *testing.T) {
 		expectedBody string
 		expectedLog  string
 		expectedErr  error
+		expectedContentType string
 	}{
 		{
 			next:         genErrorHandler(http.StatusNotFound, nil, ""),
@@ -205,6 +214,15 @@ func TestGenericErrorPage(t *testing.T) {
 			expectedBody: notFoundErrorContent,
 			expectedLog:  "",
 			expectedErr:  nil,
+			expectedContentType: "text/html; charset=utf-8",
+		},
+		{
+			next:         genErrorHandler(http.StatusBadRequest, nil, ""),
+			expectedCode: 0,
+			expectedBody: badRequestErrorJSONContent,
+			expectedLog:  "",
+			expectedErr:  nil,
+			expectedContentType: "application/json",
 		},
 		{
 			next:         genErrorHandler(http.StatusInternalServerError, nil, ""),
@@ -212,6 +230,7 @@ func TestGenericErrorPage(t *testing.T) {
 			expectedBody: genericErrorContent,
 			expectedLog:  "",
 			expectedErr:  nil,
+			expectedContentType:"text/html; charset=utf-8",
 		},
 	}
 
@@ -238,6 +257,10 @@ func TestGenericErrorPage(t *testing.T) {
 			t.Errorf("Test %d: Expected body %q, but got %q",
 				i, test.expectedBody, body)
 		}
+		if contentType := rec.Header().Get("Content-Type"); contentType != test.expectedContentType{
+			t.Errorf("Test %d: Expected Content-Type %s, but got %s",
+				i, test.expectedContentType, contentType)
+		}
 		if log := buf.String(); !strings.Contains(log, test.expectedLog) {
 			t.Errorf("Test %d: Expected log %q, but got %q",
 				i, test.expectedLog, log)