feat: return header for error ID

.gitignore

@@ -15,3 +15,4 @@ _book/
 dist/
 coverage.*
 .bin
+.claude/

json.go

@@ -17,6 +17,10 @@ type ErrorContainer struct {
 	Error *DefaultError `json:"error"`
 }
 
+func (e *ErrorContainer) ID() string {
+	return e.Error.ID()
+}
+
 type ErrorReporter interface {
 	ReportError(r *http.Request, code int, err error, args ...interface{})
 }
@@ -159,13 +163,15 @@ func (h *JSONWriter) WriteErrorCode(w http.ResponseWriter, r *http.Request, code
 	}
 
 	w.Header().Set("Content-Type", "application/json")
-	w.WriteHeader(code)
 
 	// Enhancing must happen after logging or context will be lost.
 	var payload interface{} = err
 	if h.ErrorEnhancer != nil {
 		payload = h.ErrorEnhancer(r, err)
 	}
+	if id, ok := payload.(interface{ ID() string }); ok {
+		w.Header().Set("Ory-Error-Id", id.ID())
+	}
 	if de, ok := payload.(*DefaultError); ok && !h.EnableDebug {
 		de2 := *de
 		de2.DebugField = ""
@@ -179,6 +185,8 @@ func (h *JSONWriter) WriteErrorCode(w http.ResponseWriter, r *http.Request, code
 		payload = ec2
 	}
 
+	w.WriteHeader(code)
+
 	if err := json.NewEncoder(w).Encode(payload); err != nil {
 		// There was an error, but there's actually not a lot we can do except log that this happened.
 		h.Reporter.ReportError(r, code, errors.WithStack(err), "Could not write ErrorContainer to response writer")

json_test.go

@@ -422,3 +422,51 @@ func TestCanceledJSON(t *testing.T) {
 	assert.Contains(t, string(body), "some unrelated error")
 	assert.Equal(t, 499, resp.StatusCode)
 }
+
+func TestOryErrorIDHeader(t *testing.T) {
+	for k, tc := range []struct {
+		name           string
+		err            error
+		expectedHeader string
+	}{
+		{
+			name:           "sets ID in header",
+			err:            &ErrMisconfiguration,
+			expectedHeader: "invalid_configuration",
+		},
+		{
+			name:           "sets empty header without ID",
+			err:            &ErrNotFound,
+			expectedHeader: "",
+		},
+		{
+			name: "custom error with ID sets header",
+			err: &DefaultError{
+				IDField:     "custom_error_id",
+				CodeField:   http.StatusBadRequest,
+				StatusField: http.StatusText(http.StatusBadRequest),
+				ErrorField:  "custom error",
+			},
+			expectedHeader: "custom_error_id",
+		},
+		{
+			name:           "upstream error sets header",
+			err:            &ErrUpstreamError,
+			expectedHeader: "upstream_error",
+		},
+	} {
+		t.Run(fmt.Sprintf("case=%d/%s", k, tc.name), func(t *testing.T) {
+			h := NewJSONWriter(nil)
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				h.WriteError(w, r, tc.err)
+			}))
+			t.Cleanup(ts.Close)
+
+			resp, err := http.Get(ts.URL + "/do")
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			assert.Equal(t, tc.expectedHeader, resp.Header.Get("Ory-Error-Id"))
+		})
+	}
+}

plain.go

@@ -87,6 +87,9 @@ func (h *TextWriter) WriteErrorCode(w http.ResponseWriter, r *http.Request, code
 	// All errors land here, so it's a really good idea to do the logging here as well!
 	h.Reporter.ReportError(r, code, err, "An error occurred while handling a request")
 
+	if id, ok := err.(interface{ ID() string }); ok {
+		w.Header().Set("Ory-Error-Id", id.ID())
+	}
 	w.Header().Set("Content-Type", h.contentType)
 	w.WriteHeader(code)
 	fmt.Fprintf(w, "%s", err)

plain_test.go

@@ -0,0 +1,62 @@
+// Copyright © 2023 Ory Corp
+// SPDX-License-Identifier: Apache-2.0
+
+package herodot
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTextWriterOryErrorIDHeader(t *testing.T) {
+	for k, tc := range []struct {
+		name           string
+		err            error
+		expectedHeader string
+	}{
+		{
+			name:           "error with ID sets header",
+			err:            &ErrMisconfiguration,
+			expectedHeader: "invalid_configuration",
+		},
+		{
+			name:           "error without ID does not set header",
+			err:            &ErrNotFound,
+			expectedHeader: "",
+		},
+		{
+			name: "custom error with ID sets header",
+			err: &DefaultError{
+				IDField:     "custom_text_error_id",
+				CodeField:   http.StatusBadRequest,
+				StatusField: http.StatusText(http.StatusBadRequest),
+				ErrorField:  "custom error",
+			},
+			expectedHeader: "custom_text_error_id",
+		},
+		{
+			name:           "upstream error sets header",
+			err:            &ErrUpstreamError,
+			expectedHeader: "upstream_error",
+		},
+	} {
+		t.Run(fmt.Sprintf("case=%d/%s", k, tc.name), func(t *testing.T) {
+			h := NewTextWriter(&stdReporter{}, "plain")
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				h.WriteError(w, r, tc.err)
+			}))
+			t.Cleanup(ts.Close)
+
+			resp, err := http.Get(ts.URL + "/do")
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			assert.Equal(t, tc.expectedHeader, resp.Header.Get("Ory-Error-Id"))
+		})
+	}
+}