log error for responseWriter.Write() call when writing conjure errors to response writer

conjure-go-contract/errors/http.go

@@ -15,10 +15,12 @@
 package errors
 
 import (
+	"context"
 	"encoding/json"
 	"net/http"
 
 	"github.com/palantir/conjure-go-runtime/v2/conjure-go-contract/codecs"
+	"github.com/palantir/witchcraft-go-logging/wlog/svclog/svc1log"
 )
 
 // WriteErrorResponse writes error to the response writer.
@@ -52,3 +54,35 @@ func WriteErrorResponse(w http.ResponseWriter, e Error) {
 	w.WriteHeader(e.Code().StatusCode())
 	_, _ = w.Write(marshaledError) // There is nothing we can do on write failure.
 }
+
+func WriteErrorResponseWithContext(ctx context.Context, w http.ResponseWriter, e Error) {
+	var marshaledError []byte
+	var err error
+
+	// First try to marshal with custom handling (if present)
+	if marshaler, ok := e.(json.Marshaler); ok {
+		marshaledError, err = codecs.JSON.Marshal(marshaler)
+	}
+	// If we fail, use best-effort conversion to SerializableError.
+	if marshaledError == nil || err != nil {
+		params, err := codecs.JSON.Marshal(mergeParams(e)) // on failure, params will be nil
+		if err != nil {
+			params = nil
+		}
+		// This should never fail, since all fields other than params are primitives
+		// and we fall back to empty params if they fail above. Nothing we can do otherwise.
+		marshaledError, _ = codecs.JSON.Marshal(SerializableError{
+			ErrorCode:       e.Code(),
+			ErrorName:       e.Name(),
+			ErrorInstanceID: e.InstanceID(),
+			Parameters:      params,
+		})
+	}
+
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(e.Code().StatusCode())
+	_, rwWriteErr := w.Write(marshaledError) // There is nothing we can do on write failure.
+	if rwWriteErr != nil {
+		svc1log.FromContext(ctx).Error("Failed to write response", svc1log.Stacktrace(rwWriteErr))
+	}
+}

conjure-go-server/httpserver/handlers.go

@@ -66,7 +66,7 @@ func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		switch e := cause.(type) {
 		case errors.Error:
 			// if error is a conjure error, use WriteErrorResponse utility
-			errors.WriteErrorResponse(w, e)
+			errors.WriteErrorResponseWithContext(r.Context(), w, e)
 		case json.Marshaler:
 			// else if error is a json marshaler, write as json
 			WriteJSONResponse(w, e, status)