Bind: return 413 status code when error is http.MaxBytesError

The Go standard library includes a method `http.MaxBytesReader` that allows limiting the request body. For example, users can create a middleware like:

```go
func MiddlewareMaxBodySize(c *gin.Context) {
	// Limit request body to 100 bytes
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 100)
	c.Next()
}
```

When the body exceeds the limit, reading from the request body returns an error of type `http.MaxBytesError`.

This PR makes sure that when the error is of kind `http.MaxBytesError`, Gin returns the correct status code 413 (Request Entity Too Large) instead of a generic 400 (Bad Request).

context.go

@@ -769,8 +769,15 @@ func (c *Context) BindUri(obj any) error {
 // It will abort the request with HTTP 400 if any error occurs.
 // See the binding package.
 func (c *Context) MustBindWith(obj any, b binding.Binding) error {
-	if err := c.ShouldBindWith(obj, b); err != nil {
+	err := c.ShouldBindWith(obj, b)
-		c.AbortWithError(http.StatusBadRequest, err).SetType(ErrorTypeBind) //nolint: errcheck
+	if err != nil {
+		maxBytesErr := &http.MaxBytesError{}
+		switch {
+		case errors.As(err, &maxBytesErr):
+			c.AbortWithError(http.StatusRequestEntityTooLarge, err).SetType(ErrorTypeBind) //nolint: errcheck
+		default:
+			c.AbortWithError(http.StatusBadRequest, err).SetType(ErrorTypeBind) //nolint: errcheck
+		}
 		return err
 	}
 	return nil

context_test.go

@@ -671,7 +671,7 @@ func TestContextDefaultQueryOnEmptyRequest(t *testing.T) {
 
 func TestContextQueryAndPostForm(t *testing.T) {
 	c, _ := CreateTestContext(httptest.NewRecorder())
-	body := bytes.NewBufferString("foo=bar&page=11&both=&foo=second")
+	body := strings.NewReader("foo=bar&page=11&both=&foo=second")
 	c.Request, _ = http.NewRequest(http.MethodPost,
 		"/?both=GET&id=main&id=omit&array[]=first&array[]=second&ids[a]=hi&ids[b]=3.14", body)
 	c.Request.Header.Add("Content-Type", MIMEPOSTForm)
@@ -946,7 +946,7 @@ func TestContextRenderJSONPWithoutCallback(t *testing.T) {
 	c.JSONP(http.StatusCreated, H{"foo": "bar"})
 
 	assert.Equal(t, http.StatusCreated, w.Code)
-	assert.Equal(t, "{\"foo\":\"bar\"}", w.Body.String())
+	assert.Equal(t, `{"foo":"bar"}`, w.Body.String())
 	assert.Equal(t, "application/json; charset=utf-8", w.Header().Get("Content-Type"))
 }
 
@@ -972,7 +972,7 @@ func TestContextRenderAPIJSON(t *testing.T) {
 	c.JSON(http.StatusCreated, H{"foo": "bar"})
 
 	assert.Equal(t, http.StatusCreated, w.Code)
-	assert.Equal(t, "{\"foo\":\"bar\"}", w.Body.String())
+	assert.Equal(t, `{"foo":"bar"}`, w.Body.String())
 	assert.Equal(t, "application/vnd.api+json", w.Header().Get("Content-Type"))
 }
 
@@ -1432,7 +1432,7 @@ func TestContextNegotiationWithJSON(t *testing.T) {
 	})
 
 	assert.Equal(t, http.StatusOK, w.Code)
-	assert.Equal(t, "{\"foo\":\"bar\"}", w.Body.String())
+	assert.Equal(t, `{"foo":"bar"}`, w.Body.String())
 	assert.Equal(t, "application/json; charset=utf-8", w.Header().Get("Content-Type"))
 }
 
@@ -1848,9 +1848,29 @@ func TestContextContentType(t *testing.T) {
 	assert.Equal(t, "application/json", c.ContentType())
 }
 
+func TestContextBindRequestTooLarge(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
+	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 10)
+
+	var obj struct {
+		Foo string `json:"foo"`
+		Bar string `json:"bar"`
+	}
+	require.Error(t, c.BindJSON(&obj))
+	c.Writer.WriteHeaderNow()
+
+	assert.Empty(t, obj.Bar)
+	assert.Empty(t, obj.Foo)
+	assert.Equal(t, http.StatusRequestEntityTooLarge, w.Code)
+	assert.True(t, c.IsAborted())
+}
+
 func TestContextAutoBindJSON(t *testing.T) {
 	c, _ := CreateTestContext(httptest.NewRecorder())
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("{\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
 	c.Request.Header.Add("Content-Type", MIMEJSON)
 
 	var obj struct {
@@ -1867,7 +1887,7 @@ func TestContextBindWithJSON(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("{\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
 	c.Request.Header.Add("Content-Type", MIMEXML) // set fake content-type
 
 	var obj struct {
@@ -1884,7 +1904,7 @@ func TestContextBindWithXML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString(`<?xml version="1.0" encoding="UTF-8"?>
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`<?xml version="1.0" encoding="UTF-8"?>
 		<root>
 			<foo>FOO</foo>
 		   	<bar>BAR</bar>
@@ -1951,7 +1971,7 @@ func TestContextBindWithQuery(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/?foo=bar&bar=foo", bytes.NewBufferString("foo=unused"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/?foo=bar&bar=foo", strings.NewReader("foo=unused"))
 
 	var obj struct {
 		Foo string `form:"foo"`
@@ -1967,7 +1987,7 @@ func TestContextBindWithYAML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("foo: bar\nbar: foo"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader("foo: bar\nbar: foo"))
 	c.Request.Header.Add("Content-Type", MIMEXML) // set fake content-type
 
 	var obj struct {
@@ -1984,7 +2004,7 @@ func TestContextBindWithTOML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("foo = 'bar'\nbar = 'foo'"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader("foo = 'bar'\nbar = 'foo'"))
 	c.Request.Header.Add("Content-Type", MIMEXML) // set fake content-type
 
 	var obj struct {
@@ -2001,7 +2021,7 @@ func TestContextBadAutoBind(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "http://example.com", bytes.NewBufferString("\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "http://example.com", strings.NewReader("\"foo\":\"bar\", \"bar\":\"foo\"}"))
 	c.Request.Header.Add("Content-Type", MIMEJSON)
 	var obj struct {
 		Foo string `json:"foo"`
@@ -2020,7 +2040,7 @@ func TestContextBadAutoBind(t *testing.T) {
 
 func TestContextAutoShouldBindJSON(t *testing.T) {
 	c, _ := CreateTestContext(httptest.NewRecorder())
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("{\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
 	c.Request.Header.Add("Content-Type", MIMEJSON)
 
 	var obj struct {
@@ -2037,7 +2057,7 @@ func TestContextShouldBindWithJSON(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("{\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
 	c.Request.Header.Add("Content-Type", MIMEXML) // set fake content-type
 
 	var obj struct {
@@ -2054,7 +2074,7 @@ func TestContextShouldBindWithXML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString(`<?xml version="1.0" encoding="UTF-8"?>
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`<?xml version="1.0" encoding="UTF-8"?>
 		<root>
 			<foo>FOO</foo>
 			<bar>BAR</bar>
@@ -2121,7 +2141,7 @@ func TestContextShouldBindWithQuery(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/?foo=bar&bar=foo&Foo=bar1&Bar=foo1", bytes.NewBufferString("foo=unused"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/?foo=bar&bar=foo&Foo=bar1&Bar=foo1", strings.NewReader("foo=unused"))
 
 	var obj struct {
 		Foo  string `form:"foo"`
@@ -2141,7 +2161,7 @@ func TestContextShouldBindWithYAML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("foo: bar\nbar: foo"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader("foo: bar\nbar: foo"))
 	c.Request.Header.Add("Content-Type", MIMEXML) // set fake content-type
 
 	var obj struct {
@@ -2158,7 +2178,7 @@ func TestContextShouldBindWithTOML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("foo='bar'\nbar= 'foo'"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader("foo='bar'\nbar= 'foo'"))
 	c.Request.Header.Add("Content-Type", MIMETOML) // set fake content-type
 
 	var obj struct {
@@ -2175,7 +2195,7 @@ func TestContextBadAutoShouldBind(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
 
-	c.Request, _ = http.NewRequest(http.MethodPost, "http://example.com", bytes.NewBufferString("\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "http://example.com", strings.NewReader(`"foo":"bar", "bar":"foo"}`))
 	c.Request.Header.Add("Content-Type", MIMEJSON)
 	var obj struct {
 		Foo string `json:"foo"`
@@ -2239,7 +2259,7 @@ func TestContextShouldBindBodyWith(t *testing.T) {
 			w := httptest.NewRecorder()
 			c, _ := CreateTestContext(w)
 			c.Request, _ = http.NewRequest(
-				http.MethodPost, "http://example.com", bytes.NewBufferString(tt.bodyA),
+				http.MethodPost, "http://example.com", strings.NewReader(tt.bodyA),
 			)
 			// When it binds to typeA and typeB, it finds the body is
 			// not typeB but typeA.
@@ -2257,7 +2277,7 @@ func TestContextShouldBindBodyWith(t *testing.T) {
 			w := httptest.NewRecorder()
 			c, _ := CreateTestContext(w)
 			c.Request, _ = http.NewRequest(
-				http.MethodPost, "http://example.com", bytes.NewBufferString(tt.bodyB),
+				http.MethodPost, "http://example.com", strings.NewReader(tt.bodyB),
 			)
 			objA := typeA{}
 			require.Error(t, c.ShouldBindBodyWith(&objA, tt.bindingA))
@@ -2603,7 +2623,7 @@ func TestContextShouldBindBodyWithPlain(t *testing.T) {
 
 func TestContextGolangContext(t *testing.T) {
 	c, _ := CreateTestContext(httptest.NewRecorder())
-	c.Request, _ = http.NewRequest(http.MethodPost, "/", bytes.NewBufferString("{\"foo\":\"bar\", \"bar\":\"foo\"}"))
+	c.Request, _ = http.NewRequest(http.MethodPost, "/", strings.NewReader(`{"foo":"bar", "bar":"foo"}`))
 	require.NoError(t, c.Err())
 	assert.Nil(t, c.Done())
 	ti, ok := c.Deadline()
@@ -2651,7 +2671,7 @@ func TestGetRequestHeaderValue(t *testing.T) {
 
 func TestContextGetRawData(t *testing.T) {
 	c, _ := CreateTestContext(httptest.NewRecorder())
-	body := bytes.NewBufferString("Fetch binary post data")
+	body := strings.NewReader("Fetch binary post data")
 	c.Request, _ = http.NewRequest(http.MethodPost, "/", body)
 	c.Request.Header.Add("Content-Type", MIMEPOSTForm)
 

gin_test.go

@@ -338,7 +338,7 @@ func TestLoadHTMLFSTestMode(t *testing.T) {
 	)
 	defer ts.Close()
 
-	res, err := http.Get(fmt.Sprintf("%s/test", ts.URL))
+	res, err := http.Get(ts.URL + "/test")
 	if err != nil {
 		t.Error(err)
 	}
@@ -358,7 +358,7 @@ func TestLoadHTMLFSDebugMode(t *testing.T) {
 	)
 	defer ts.Close()
 
-	res, err := http.Get(fmt.Sprintf("%s/test", ts.URL))
+	res, err := http.Get(ts.URL + "/test")
 	if err != nil {
 		t.Error(err)
 	}
@@ -378,7 +378,7 @@ func TestLoadHTMLFSReleaseMode(t *testing.T) {
 	)
 	defer ts.Close()
 
-	res, err := http.Get(fmt.Sprintf("%s/test", ts.URL))
+	res, err := http.Get(ts.URL + "/test")
 	if err != nil {
 		t.Error(err)
 	}
@@ -405,7 +405,7 @@ func TestLoadHTMLFSUsingTLS(t *testing.T) {
 		},
 	}
 	client := &http.Client{Transport: tr}
-	res, err := client.Get(fmt.Sprintf("%s/test", ts.URL))
+	res, err := client.Get(ts.URL + "/test")
 	if err != nil {
 		t.Error(err)
 	}
@@ -425,7 +425,7 @@ func TestLoadHTMLFSFuncMap(t *testing.T) {
 	)
 	defer ts.Close()
 
-	res, err := http.Get(fmt.Sprintf("%s/raw", ts.URL))
+	res, err := http.Get(ts.URL + "/raw")
 	if err != nil {
 		t.Error(err)
 	}