Fix Result[T] status code inconsistency when both Code and Err are set

edge_cases_test.go

@@ -0,0 +1,100 @@
+package m
+
+import (
+	"errors"
+	"net/http/httptest"
+	"testing"
+)
+
+// TestResultEdgeCases tests edge cases for Result handling
+func TestResultEdgeCases(t *testing.T) {
+	Reset()
+
+	t.Run("Result with zero Code should default to 200", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Code: 0,  // Zero value
+				Data: "test data",
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		// Should default to 200 OK
+		if rec.Code != 200 {
+			t.Errorf("expected HTTP status 200, got %d", rec.Code)
+		}
+	})
+
+	t.Run("Result with negative Code should be handled", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Code: -1,  // Invalid negative code
+				Data: "test",
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		t.Logf("Response Code: %d", rec.Code)
+		// Negative codes should be handled - ResponseWriter will convert to 200
+	})
+
+	t.Run("Result with both Data and Err - should prioritize Err", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Code: 500,
+				Data: "this should not appear",
+				Err:  errors.New("error occurred"),
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		if rec.Code != 500 {
+			t.Errorf("expected HTTP status 500, got %d", rec.Code)
+		}
+
+		// Should return error, not data
+		if rec.Body.String() == "this should not appear" {
+			t.Error("should not return data when error is set")
+		}
+
+		// Should contain error JSON
+		var httpErr HTTPError
+		parseJSONResponse(t, rec.Body.Bytes(), &httpErr)
+		if httpErr.Code != 500 {
+			t.Errorf("expected error code 500 in JSON, got %d", httpErr.Code)
+		}
+	})
+
+	t.Run("Result with invalid status code and Err - should use inferred code", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Code: 9999,  // Invalid status code
+				Err:  errors.New("not found"),
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		// Should use inferred code (404 from "not found") instead of invalid 9999
+		if rec.Code != 404 {
+			t.Errorf("expected HTTP status 404 (inferred), got %d", rec.Code)
+		}
+
+		var httpErr HTTPError
+		parseJSONResponse(t, rec.Body.Bytes(), &httpErr)
+		if httpErr.Code != 404 {
+			t.Errorf("expected error code 404 in JSON, got %d", httpErr.Code)
+		}
+	})
+}

mint.go

@@ -855,18 +855,31 @@ func handleResult(w http.ResponseWriter, result Result[any]) error {
 		WriteHeaders(w, result.Headers)
 	}
 
-	if result.Code != 0 {
-		w.WriteHeader(result.Code)
-	}
-
 	if result.Err != nil {
+		// If both Code and Err are set, use the explicit Code for the error response
+		if result.Code != 0 {
+			return handleErrorWithCode(w, result.Err, result.Code)
+		}
 		return handleError(w, result.Err)
 	}
 
+	if result.Code != 0 {
+		w.WriteHeader(result.Code)
+	}
+
 	return handleCommonTypes(w, result.Data)
 }
 
+// handleError handles error responses with automatic status code inference.
+// It delegates to handleErrorWithCode with statusCode=0 to use inferred codes.
 func handleError(w http.ResponseWriter, err error) error {
+	return handleErrorWithCode(w, err, 0)
+}
+
+// handleErrorWithCode handles error responses with an optional explicit status code.
+// If statusCode is 0, the status is inferred from the error type/message.
+// If statusCode is provided, it overrides the inferred status code.
+func handleErrorWithCode(w http.ResponseWriter, err error, statusCode int) error {
 	if errorHandler() != nil {
 		errorHandler()(w, err)
 		return nil
@@ -882,6 +895,16 @@ func handleError(w http.ResponseWriter, err error) error {
 		return nil
 	}
 
+	// If an explicit status code is provided, use it instead of the inferred one
+	// Status codes should be in the valid HTTP range (100-599)
+	if statusCode != 0 {
+		if statusCode < 100 || statusCode > 599 {
+			logger().Printf("warning: invalid HTTP status code %d, using inferred code %d", statusCode, httpErr.Code)
+		} else {
+			httpErr.Code = statusCode
+		}
+	}
+
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
 
 	if !statusWritten {

mint_test.go

@@ -1966,3 +1966,86 @@ func TestCompleteConfigurationScenario(t *testing.T) {
 		}
 	})
 }
+
+// ========== Bug Fix Tests ==========
+
+// TestResultWithCodeAndErr tests the fix for the bug where Result[T] with both
+// Code and Err set would write status codes twice, causing inconsistency
+func TestResultWithCodeAndErr(t *testing.T) {
+	Reset()
+
+	t.Run("Result with both Code and Err - should use explicit Code", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Code: 403,  // Forbidden - should be used
+				Err:  errors.New("access denied"),
+				Data: "should not be returned",
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		t.Logf("Status Code: %d", rec.Code)
+		t.Logf("Response Body: %s", rec.Body.String())
+
+		// Fixed: Both HTTP status and error JSON code should be 403
+		if rec.Code != 403 {
+			t.Errorf("expected HTTP status 403, got %d", rec.Code)
+		}
+
+		var errResp HTTPError
+		parseJSONResponse(t, rec.Body.Bytes(), &errResp)
+		if errResp.Code != 403 {
+			t.Errorf("expected error code 403 in JSON, got %d", errResp.Code)
+		}
+	})
+
+	t.Run("Result with only Err - should infer code", func(t *testing.T) {
+		handler := H(func() Result[string] {
+			return Result[string]{
+				Err: errors.New("something went wrong"),
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		// Should infer 500 from generic error
+		if rec.Code != 500 {
+			t.Errorf("expected HTTP status 500, got %d", rec.Code)
+		}
+
+		var errResp HTTPError
+		parseJSONResponse(t, rec.Body.Bytes(), &errResp)
+		if errResp.Code != 500 {
+			t.Errorf("expected error code 500 in JSON, got %d", errResp.Code)
+		}
+	})
+
+	t.Run("Result with Code and Data - no error", func(t *testing.T) {
+		handler := H(func() Result[map[string]string] {
+			return Result[map[string]string]{
+				Code: 201,
+				Data: map[string]string{"status": "created"},
+			}
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest("GET", "/", nil)
+		handler(rec, req)
+
+		if rec.Code != 201 {
+			t.Errorf("expected HTTP status 201, got %d", rec.Code)
+		}
+
+		var resp map[string]string
+		parseJSONResponse(t, rec.Body.Bytes(), &resp)
+		if resp["status"] != "created" {
+			t.Errorf("expected status=created in response")
+		}
+	})
+}
+