Sub2API v1.0 - AI API 网关（二开初始版本，基于上游 Wei-Shaw/sub2api）

backend/internal/handler/gateway_handler_error_fallback_test.go

@@ -0,0 +1,184 @@
+package handler
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGatewayEnsureForwardErrorResponse_WritesFallbackWhenNotWritten(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, false)
+
+	require.True(t, wrote)
+	require.Equal(t, http.StatusBadGateway, w.Code)
+
+	var parsed map[string]any
+	err := json.Unmarshal(w.Body.Bytes(), &parsed)
+	require.NoError(t, err)
+	assert.Equal(t, "error", parsed["type"])
+	errorObj, ok := parsed["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errorObj["type"])
+	assert.Equal(t, "Upstream request failed", errorObj["message"])
+}
+
+// Writer 已写后 ensureForwardErrorResponse 必须把错误以 SSE 形式追加，
+// 而不是 silent EOF。非 /responses 路径走 legacy data:{"type":"error"} 分支。
+func TestGatewayEnsureForwardErrorResponse_AppendsSSEAfterWritten(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+	c.String(http.StatusTeapot, "already written")
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, false)
+
+	require.True(t, wrote)
+	require.Equal(t, http.StatusTeapot, w.Code)
+	assert.Contains(t, w.Body.String(), "already written")
+	assert.Contains(t, w.Body.String(), `data: {"type":"error"`)
+}
+
+func TestGatewayEnsureForwardErrorResponse_SkipsCommittedSSEError(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodPost, EndpointResponses, nil)
+	c.Header("Content-Type", "text/event-stream")
+	_, _ = c.Writer.WriteString("event: error\ndata: {\"type\":\"error\"}\n\n")
+	service.MarkResponseCommitted(c)
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, true)
+
+	require.False(t, wrote)
+	require.Equal(t, 1, strings.Count(w.Body.String(), "event: error"))
+}
+
+// case B 回归：Anthropic-backed /responses，Writer 已被写过时
+// ensureForwardErrorResponse 仍要发 response.failed。
+func TestGatewayEnsureForwardErrorResponse_ResponsesRouteAfterWrittenEmitsResponseFailed(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodPost, EndpointResponses, nil)
+	_, _ = c.Writer.WriteString(":\n\n")
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, false)
+
+	require.True(t, wrote)
+	body := w.Body.String()
+	assert.Contains(t, body, ":\n\n")
+	assert.Contains(t, body, "event: response.failed\n")
+	assert.Contains(t, body, `"type":"response.failed"`)
+}
+
+func TestGatewayForwardErrorAlreadyCommunicated(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	t.Run("json error already written", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+		before := c.Writer.Size()
+		c.JSON(http.StatusBadGateway, gin.H{
+			"type": "error",
+			"error": gin.H{
+				"type":    "upstream_error",
+				"message": "Your Claude Code version (2.1.39) is below the minimum required version (2.1.81). Please update: npm update -g @anthropic-ai/claude-code",
+			},
+		})
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, before, errors.New("upstream error: 400 message=version too low"))
+
+		require.True(t, reported)
+		body := w.Body.String()
+		assert.NotContains(t, body, `data: {"type":"error"`)
+	})
+
+	t.Run("sse ping still needs fallback", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+		c.Header("Content-Type", "text/event-stream")
+		before := c.Writer.Size()
+		_, _ = c.Writer.WriteString(":\n\n")
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, before, errors.New("stream read error: unexpected EOF"))
+
+		require.False(t, reported)
+	})
+
+	t.Run("no write still needs fallback", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, c.Writer.Size(), errors.New("upstream request failed"))
+
+		require.False(t, reported)
+	})
+
+	// apikey 场景核心回归：复刻 GatewayService.handleErrorResponse 的 case 400 ——
+	// 原样透传上游 JSON body 后返回 err。此时错误已经完整告知客户端，
+	// handler 不得再追加 data:{"type":"error"} 帧，否则响应被污染成「JSON + 一行 data:」。
+	t.Run("upstream 400 json passthrough via c.Data", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+		before := c.Writer.Size()
+		upstreamBody := []byte(`{"type":"error","error":{"type":"upstream_error","message":"Your Claude Code version (2.1.39) is below the minimum required version (2.1.81). Please update: npm update -g @anthropic-ai/claude-code"}}`)
+		c.Data(http.StatusBadRequest, "application/json", upstreamBody)
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, before, errors.New("upstream error: 400 message=version too low"))
+
+		require.True(t, reported)
+		body := w.Body.String()
+		assert.NotContains(t, body, `data: {"type":"error"`)
+		// 客户端只应收到上游那一份错误，没有被追加第二份。
+		assert.Equal(t, 1, strings.Count(body, `"type":"error"`))
+	})
+
+	// 流式已开始（已 flush 真实 SSE 事件，不只是 ping）+ 上游中途 400：
+	// HTTP 200 已固化，仍需 handler 补协议级终止帧，故不算「已完整告知」。
+	t.Run("streaming 400 mid-stream still needs fallback", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+		c.Header("Content-Type", "text/event-stream")
+		before := c.Writer.Size()
+		_, _ = c.Writer.WriteString("event: message_start\ndata: {\"type\":\"message_start\"}\n\n")
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, before, errors.New("upstream error: 400 message=version too low"))
+
+		require.False(t, reported)
+	})
+
+	// 防御边界：err 为 nil 时永远不算「已告知」，避免在成功路径误吞兜底逻辑。
+	t.Run("nil error never reports communicated", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodPost, EndpointMessages, nil)
+		c.JSON(http.StatusOK, gin.H{"ok": true})
+
+		reported := gatewayForwardErrorAlreadyCommunicated(c, 0, nil)
+
+		require.False(t, reported)
+	})
+}