Merge cd9b91bb2ef67d3b409e8c2465c806a2d68f5178 into d3ffc9985281dcf4d3bef604cce4e662b1a327a6

binding/json.go

@@ -7,6 +7,7 @@ package binding
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 
@@ -50,7 +51,12 @@ func decodeJSON(r io.Reader, obj any) error {
 		decoder.DisallowUnknownFields()
 	}
 	if err := decoder.Decode(obj); err != nil {
+		if errors.Is(err, io.EOF) {
+			return fmt.Errorf("empty request body: %w", err)
+		}
+
 		return err
 	}
+
 	return validate(obj)
 }

binding/json_external_test.go

@@ -0,0 +1,39 @@
+package binding_test
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestJSONBindingEmptyBodyReturnsHelpfulError(t *testing.T) {
+	type Req struct {
+		Name string `json:"name" binding:"required"`
+	}
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+
+	req, err := http.NewRequest(http.MethodPost, "/", bytes.NewBuffer(nil))
+	require.NoError(t, err)
+	req.Header.Set("Content-Type", "application/json")
+
+	c.Request = req
+
+	var r Req
+	err = c.ShouldBindJSON(&r)
+
+	require.Error(t, err)
+
+	// Error message should be more descriptive than plain EOF,
+	// while still preserving io.EOF via wrapping.
+	assert.NotEqual(t, "EOF", err.Error())
+	assert.Contains(t, err.Error(), "empty request body")
+	assert.ErrorIs(t, err, io.EOF)
+}