feat: add project-owned error catalogs and HTTP 200 failure contracts

middleware/idempotency.go

@@ -31,6 +31,7 @@ type IdempotencyConfig struct {
 
 type replay struct {
 	fingerprint     [32]byte
+	errorCode       string
 	status          int
 	headers         http.Header
 	body            []byte
@@ -150,8 +151,12 @@ func (i *Idempotency) Middleware() httpx.Middleware {
 					return apierrors.New(409, "IDEMPOTENCY_UNAVAILABLE", "request is in progress or its outcome cannot be replayed")
 				}
 				status, headers, data := saved.status, saved.headers.Clone(), append([]byte(nil), saved.body...)
+				errorCode := saved.errorCode
 				i.mu.Unlock()
 				headers.Set("Idempotency-Replayed", "true")
+				if errorCode != "" {
+					c.RecordError(apierrors.New(status, errorCode, ""))
+				}
 				return c.WriteResponse(status, headers, data)
 			}
 			if len(i.items) >= i.config.MaxEntries {
@@ -171,6 +176,9 @@ func (i *Idempotency) Middleware() httpx.Middleware {
 				saved.failed = true
 				saved.expires = i.now().Add(i.config.TTL)
 				size := buffer.body.Len()
+				if failure := c.Failure(); failure != nil {
+					size += len(failure.Code)
+				}
 				for k, values := range buffer.headers {
 					size += len(k)
 					for _, v := range values {
@@ -180,6 +188,9 @@ func (i *Idempotency) Middleware() httpx.Middleware {
 				if buffer.complete && buffer.err == nil && buffer.status < 500 && buffer.headers.Get("Set-Cookie") == "" && !strings.Contains(strings.ToLower(buffer.headers.Get("Cache-Control")), "no-store") && size <= i.config.MaxBytes-i.bytes {
 					saved.failed = false
 					saved.status = buffer.status
+					if failure := c.Failure(); failure != nil {
+						saved.errorCode = failure.Code
+					}
 					saved.headers = buffer.headers.Clone()
 					saved.body = append([]byte(nil), buffer.body.Bytes()...)
 					saved.size = size
@@ -202,6 +213,9 @@ func (i *Idempotency) Middleware() httpx.Middleware {
 			if buffer.status == 0 {
 				buffer.status = 200
 			}
+			if failure := child.Failure(); failure != nil {
+				c.RecordError(failure)
+			}
 			buffer.complete = true
 			return c.WriteResponse(buffer.status, buffer.headers, buffer.body.Bytes())
 		}