fix: Unwrap joinErr in gin.Error()

Author: arshukla98

errors.go

@@ -5,6 +5,7 @@
 package gin
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"strings"
@@ -165,11 +166,32 @@ func (a errorMsgs) String() string {
 		return ""
 	}
 	var buffer strings.Builder
-	for i, msg := range a {
-		fmt.Fprintf(&buffer, "Error #%02d: %s\n", i+1, msg.Err)
-		if msg.Meta != nil {
-			fmt.Fprintf(&buffer, "     Meta: %v\n", msg.Meta)
+	count := 1
+	for _, msg := range a {
+		for _, err := range unwrapJoinErr(msg.Err) {
+			fmt.Fprintf(&buffer, "Error #%02d: %s\n", count, err)
+			if msg.Meta != nil {
+				fmt.Fprintf(&buffer, "     Meta: %v\n", msg.Meta)
+			}
+			count++
 		}
 	}
 	return buffer.String()
 }
+
+func unwrapJoinErr(err error) []error {
+	if err == nil {
+		return nil
+	}
+	var result []error
+	if multi, ok := err.(interface{ Unwrap() []error }); ok {
+		for _, e := range multi.Unwrap() {
+			result = append(result, unwrapJoinErr(e)...)
+		}
+	} else if single := errors.Unwrap(err); single != nil {
+		result = append(result, unwrapJoinErr(single)...)
+	} else {
+		result = append(result, err)
+	}
+	return result
+}

errors_test.go

@@ -7,6 +7,7 @@ package gin
 import (
 	"errors"
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/gin-gonic/gin/internal/json"
@@ -138,3 +139,24 @@ func TestErrorUnwrap(t *testing.T) {
 	var testErrNonPointer TestErr
 	require.ErrorAs(t, wrappedErr, &testErrNonPointer)
 }
+
+func TestErrorJoinFormatting(t *testing.T) {
+	// Create a context with errorMsgs slice
+	c, _ := CreateTestContext(nil)
+
+	// Create a joined error
+	err1 := errors.New("service error")
+	err2 := errors.New("store error")
+	joined := errors.Join(err1, err2)
+
+	// Add to context errors
+	c.Error(joined)
+
+	// Call String(), which should now unwrap and format both
+	output := c.Errors.String()
+
+	// Check that both individual errors appear separately
+	if !strings.Contains(output, "Error #01: service error") || !strings.Contains(output, "Error #02: store error") {
+		t.Errorf("expected unwrapped errors in output, got:\n%s", output)
+	}
+}