fix: capture jikan api error body in api error struct

integrations/jikan/transport/client.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"strconv"
@@ -34,6 +35,7 @@ type Config struct {
 type APIError struct {
 	StatusCode int
 	URL        string
+	Body       json.RawMessage
 }
 
 func (e *APIError) Error() string {
@@ -177,7 +179,7 @@ func handleRequestRetry(ctx context.Context, err error, attempt int, maxRetries
 
 func handleResponseRetry(ctx context.Context, resp *http.Response, urlStr string, out any, attempt int, maxRetries int) (int, bool, error) {
 	if resp.StatusCode != http.StatusOK {
-		return handleStatusRetry(ctx, resp, urlStr, out, attempt, maxRetries)
+		return handleStatusRetry(ctx, resp, urlStr, attempt, maxRetries)
 	}
 
 	err := json.NewDecoder(resp.Body).Decode(out)
@@ -195,7 +197,7 @@ func handleResponseRetry(ctx context.Context, resp *http.Response, urlStr string
 	return resp.StatusCode, false, fmt.Errorf("failed to decode jikan response: %w", err)
 }
 
-func handleStatusRetry(ctx context.Context, resp *http.Response, urlStr string, out any, attempt int, maxRetries int) (int, bool, error) {
+func handleStatusRetry(ctx context.Context, resp *http.Response, urlStr string, attempt int, maxRetries int) (int, bool, error) {
 	statusCode := resp.StatusCode
 	apiErr := &APIError{StatusCode: statusCode, URL: urlStr}
 
@@ -211,13 +213,27 @@ func handleStatusRetry(ctx context.Context, resp *http.Response, urlStr string,
 		return statusCode, true, nil
 	}
 
-	// Best-effort decode (often useful for debugging), but still treat non-200 as error.
-	if err := json.NewDecoder(resp.Body).Decode(out); err != nil {
-		return statusCode, false, errors.Join(apiErr, fmt.Errorf("failed to decode error response: %w", err))
-	}
+	apiErr.Body = readErrorBody(resp)
 	return statusCode, false, apiErr
 }
 
+func readErrorBody(resp *http.Response) json.RawMessage {
+	if resp.Body == nil {
+		return nil
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil
+	}
+	body = []byte(strings.TrimSpace(string(body)))
+	if len(body) == 0 || !json.Valid(body) {
+		return nil
+	}
+
+	return json.RawMessage(body)
+}
+
 func isRetryableStatus(statusCode int) bool {
 	if statusCode == http.StatusTooManyRequests {
 		return true

integrations/jikan/transport/client_test.go

@@ -0,0 +1,55 @@
+package transport
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func TestHandleStatusRetryLeavesOutputUntouched(t *testing.T) {
+	out := struct {
+		Data []struct {
+			MalID int `json:"mal_id"`
+		} `json:"data"`
+	}{
+		Data: []struct {
+			MalID int `json:"mal_id"`
+		}{{MalID: 123}},
+	}
+	resp := &http.Response{
+		StatusCode: http.StatusNotFound,
+		Body:       io.NopCloser(strings.NewReader(`{"data":[{"mal_id":999}]}`)),
+		Header:     make(http.Header),
+	}
+
+	statusCode, retry, err := handleResponseRetry(context.Background(), resp, "https://example.test/anime/1", &out, 0, 1)
+	if statusCode != http.StatusNotFound {
+		t.Fatalf("statusCode = %d, want %d", statusCode, http.StatusNotFound)
+	}
+	if retry {
+		t.Fatal("retry = true, want false")
+	}
+	var apiErr *APIError
+	if !errors.As(err, &apiErr) {
+		t.Fatalf("err = %v, want APIError", err)
+	}
+	if len(out.Data) != 1 || out.Data[0].MalID != 123 {
+		t.Fatalf("out = %+v, want original value", out)
+	}
+
+	var body struct {
+		Data []struct {
+			MalID int `json:"mal_id"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(apiErr.Body, &body); err != nil {
+		t.Fatalf("unmarshal APIError body: %v", err)
+	}
+	if len(body.Data) != 1 || body.Data[0].MalID != 999 {
+		t.Fatalf("APIError body = %+v, want decoded error body", body)
+	}
+}