🐛 fix: Nil pointer dereference with Must Bind binding (#3171)

* Fix nil pointer dereference with Must Bind binding error

if err is nil err.Error() panics
(eg. c.Bind().Must().JSON(...) successfully binds but panics

* Added returnErr test

make sure returnErr works with nil error

* Reordered returnErr nil check

as in majority of cases we expect err to be nil, this should provide better short-cutting

* Use require.NoError

* Update bind_test.go

* Renamed Must to WithAutoHandling

* Update bind.md

Added a requested clarification

* renamed Should to WithoutAutoHandling and Bind.should to Bind.dontHandle

* renamed dontHandle to dontHandleErrs

* fixed formatting

* fixed a typo

* Update binder documentation

---------

Co-authored-by: Juan Calderon-Perez <[email protected]>

bind.go

@@ -19,34 +19,35 @@ type StructValidator interface {
 
 // Bind struct
 type Bind struct {
-	ctx    Ctx
-	should bool
+	ctx            Ctx
+	dontHandleErrs bool
 }
 
-// Should To handle binder errors manually, you can prefer Should method.
+// If you want to handle binder errors manually, you can use `WithoutAutoHandling`.
 // It's default behavior of binder.
-func (b *Bind) Should() *Bind {
-	b.should = true
+func (b *Bind) WithoutAutoHandling() *Bind {
+	b.dontHandleErrs = true
 
 	return b
 }
 
-// Must If you want to handle binder errors automatically, you can use Must.
-// If there's an error it'll return error and 400 as HTTP status.
-func (b *Bind) Must() *Bind {
-	b.should = false
+// If you want to handle binder errors automatically, you can use `WithAutoHandling`.
+// If there's an error, it will return the error and set HTTP status to `400 Bad Request`.
+// You must still return on error explicitly
+func (b *Bind) WithAutoHandling() *Bind {
+	b.dontHandleErrs = false
 
 	return b
 }
 
-// Check Should/Must errors and return it by usage.
+// Check WithAutoHandling/WithoutAutoHandling errors and return it by usage.
 func (b *Bind) returnErr(err error) error {
-	if !b.should {
-		b.ctx.Status(StatusBadRequest)
-		return NewError(StatusBadRequest, "Bad request: "+err.Error())
+	if err == nil || b.dontHandleErrs {
+		return err
 	}
 
-	return err
+	b.ctx.Status(StatusBadRequest)
+	return NewError(StatusBadRequest, "Bad request: "+err.Error())
 }
 
 // Struct validation.
@@ -62,7 +63,7 @@ func (b *Bind) validateStruct(out any) error {
 // Custom To use custom binders, you have to use this method.
 // You can register them from RegisterCustomBinder method of Fiber instance.
 // They're checked by name, if it's not found, it will return an error.
-// NOTE: Should/Must is still valid for Custom binders.
+// NOTE: WithAutoHandling/WithAutoHandling is still valid for Custom binders.
 func (b *Bind) Custom(name string, dest any) error {
 	binders := b.ctx.App().customBinders
 	for _, customBinder := range binders {
@@ -92,7 +93,7 @@ func (b *Bind) RespHeader(out any) error {
 	return b.validateStruct(out)
 }
 
-// Cookie binds the requesr cookie strings into the struct, map[string]string and map[string][]string.
+// Cookie binds the request cookie strings into the struct, map[string]string and map[string][]string.
 // NOTE: If your cookie is like key=val1,val2; they'll be binded as an slice if your map is map[string][]string. Else, it'll use last element of cookie.
 func (b *Bind) Cookie(out any) error {
 	if err := b.returnErr(binder.CookieBinder.Bind(b.ctx.RequestCtx(), out)); err != nil {

bind_test.go

@@ -19,6 +19,15 @@ import (
 
 const helloWorld = "hello world"
 
+// go test -run Test_returnErr -v
+func Test_returnErr(t *testing.T) {
+	app := New()
+	c := app.AcquireCtx(&fasthttp.RequestCtx{})
+
+	err := c.Bind().WithAutoHandling().returnErr(nil)
+	require.NoError(t, err)
+}
+
 // go test -run Test_Bind_Query -v
 func Test_Bind_Query(t *testing.T) {
 	t.Parallel()
@@ -1616,8 +1625,8 @@ func Test_Bind_CustomBinder(t *testing.T) {
 	require.Equal(t, "john", d.Name)
 }
 
-// go test -run Test_Bind_Must
-func Test_Bind_Must(t *testing.T) {
+// go test -run Test_Bind_WithAutoHandling
+func Test_Bind_WithAutoHandling(t *testing.T) {
 	app := New()
 	c := app.AcquireCtx(&fasthttp.RequestCtx{})
 
@@ -1626,7 +1635,7 @@ func Test_Bind_Must(t *testing.T) {
 	}
 	rq := new(RequiredQuery)
 	c.Request().URI().SetQueryString("")
-	err := c.Bind().Must().Query(rq)
+	err := c.Bind().WithAutoHandling().Query(rq)
 	require.Equal(t, StatusBadRequest, c.Response().StatusCode())
 	require.Equal(t, "Bad request: bind: name is empty", err.Error())
 }

binder/README.md

@@ -1,17 +1,19 @@
 # Fiber Binders
 
-Binder is a new request/response binding feature for Fiber. Against the old Fiber parsers, it supports custom binder registration, struct validation, `map[string]string`, `map[string][]string`, and more. It's introduced in Fiber v3 and a replacement of:
+**Binder** is a new request/response binding feature for Fiber introduced in Fiber v3. It replaces the old Fiber parsers and offers enhanced capabilities such as custom binder registration, struct validation, support for `map[string]string`, `map[string][]string`, and more. Binder replaces the following components:
 
-- BodyParser
-- ParamsParser
-- GetReqHeaders
-- GetRespHeaders
-- AllParams
-- QueryParser
-- ReqHeaderParser
+- `BodyParser`
+- `ParamsParser`
+- `GetReqHeaders`
+- `GetRespHeaders`
+- `AllParams`
+- `QueryParser`
+- `ReqHeaderParser`
 
 ## Default Binders
 
+Fiber provides several default binders out of the box:
+
 - [Form](form.go)
 - [Query](query.go)
 - [URI](uri.go)
@@ -23,12 +25,12 @@ Binder is a new request/response binding feature for Fiber. Against the old Fibe
 
 ## Guides
 
-### Binding into the Struct
+### Binding into a Struct
 
-Fiber supports binding into the struct with [gorilla/schema](https://github.com/gorilla/schema). Here's an example:
+Fiber supports binding request data directly into a struct using [gorilla/schema](https://github.com/gorilla/schema). Here's an example:
 
 ```go
-// Field names should start with an uppercase letter
+// Field names must start with an uppercase letter
 type Person struct {
     Name string `json:"name" xml:"name" form:"name"`
     Pass string `json:"pass" xml:"pass" form:"pass"`
@@ -41,56 +43,63 @@ app.Post("/", func(c fiber.Ctx) error {
         return err
     }
 
-    log.Println(p.Name) // john
-    log.Println(p.Pass) // doe
+    log.Println(p.Name) // Output: john
+    log.Println(p.Pass) // Output: doe
 
-    // ...
+    // Additional logic...
 })
 
 // Run tests with the following curl commands:
 
-// curl -X POST -H "Content-Type: application/json" --data "{\"name\":\"john\",\"pass\":\"doe\"}" localhost:3000
+// JSON
+curl -X POST -H "Content-Type: application/json" --data "{\"name\":\"john\",\"pass\":\"doe\"}" localhost:3000
 
-// curl -X POST -H "Content-Type: application/xml" --data "<login><name>john</name><pass>doe</pass></login>" localhost:3000
+// XML
+curl -X POST -H "Content-Type: application/xml" --data "<login><name>john</name><pass>doe</pass></login>" localhost:3000
 
-// curl -X POST -H "Content-Type: application/x-www-form-urlencoded" --data "name=john&pass=doe" localhost:3000
+// URL-Encoded Form
+curl -X POST -H "Content-Type: application/x-www-form-urlencoded" --data "name=john&pass=doe" localhost:3000
 
-// curl -X POST -F name=john -F pass=doe http://localhost:3000
+// Multipart Form
+curl -X POST -F name=john -F pass=doe http://localhost:3000
 
-// curl -X POST "http://localhost:3000/?name=john&pass=doe"
+// Query Parameters
+curl -X POST "http://localhost:3000/?name=john&pass=doe"
 ```
 
-### Binding into the Map
+### Binding into a Map
 
-Fiber supports binding into the `map[string]string` or `map[string][]string`. Here's an example:
+Fiber allows binding request data into a `map[string]string` or `map[string][]string`. Here's an example:
 
 ```go
 app.Get("/", func(c fiber.Ctx) error {
-    p := make(map[string][]string)
+    params := make(map[string][]string)
 
-    if err := c.Bind().Query(p); err != nil {
+    if err := c.Bind().Query(params); err != nil {
         return err
     }
 
-    log.Println(p["name"])     // john
-    log.Println(p["pass"])     // doe
-    log.Println(p["products"]) // [shoe, hat]
+    log.Println(params["name"])     // Output: [john]
+    log.Println(params["pass"])     // Output: [doe]
+    log.Println(params["products"]) // Output: [shoe hat]
 
-    // ...
+    // Additional logic...
+    return nil
 })
+
 // Run tests with the following curl command:
 
-// curl "http://localhost:3000/?name=john&pass=doe&products=shoe,hat"
+curl "http://localhost:3000/?name=john&pass=doe&products=shoe&products=hat"
 ```
 
-### Behaviors of Should/Must
+### Automatic Error Handling with `WithAutoHandling`
 
-Normally, Fiber returns binder error directly. However; if you want to handle it automatically, you can prefer `Must()`.
+By default, Fiber returns binder errors directly. To handle errors automatically and return a `400 Bad Request` status, use the `WithAutoHandling()` method.
 
-If there's an error it'll return error and 400 as HTTP status. Here's an example for it:
+**Example:**
 
 ```go
-// Field names should start with an uppercase letter
+// Field names must start with an uppercase letter
 type Person struct {
     Name string `json:"name,required"`
     Pass string `json:"pass"`
@@ -99,23 +108,24 @@ type Person struct {
 app.Get("/", func(c fiber.Ctx) error {
     p := new(Person)
 
-    if err := c.Bind().Must().JSON(p); err != nil {
+    if err := c.Bind().WithAutoHandling().JSON(p); err != nil {
         return err 
-        // Status code: 400 
+        // Automatically returns status code 400
         // Response: Bad request: name is empty
     }
 
-    // ...
+    // Additional logic...
+    return nil
 })
 
 // Run tests with the following curl command:
 
-// curl -X GET -H "Content-Type: application/json" --data "{\"pass\":\"doe\"}" localhost:3000
+curl -X GET -H "Content-Type: application/json" --data "{\"pass\":\"doe\"}" localhost:3000
 ```
 
-### Defining Custom Binder
+### Defining a Custom Binder
 
-We didn't add much binder to make Fiber codebase minimal. If you want to use your own binders, it's easy to register and use them. Here's an example for TOML binder.
+Fiber maintains a minimal codebase by not including every possible binder. If you need to use a custom binder, you can easily register and utilize it. Here's an example of creating a `toml` binder.
 
 ```go
 type Person struct {
@@ -147,24 +157,26 @@ func main() {
             return err
         }
 
-        // or you can use like:
+        // Alternatively, specify the custom binder:
         // if err := c.Bind().Custom("toml", out); err != nil {
-        //      return err
+        //     return err
         // }
 
-        return c.SendString(out.Pass) // test
+        return c.SendString(out.Pass) // Output: test
     })
 
     app.Listen(":3000")
 }
 
-// curl -X GET -H "Content-Type: application/toml" --data "name = 'bar'
-// pass = 'test'" localhost:3000
+// Run tests with the following curl command:
+
+curl -X GET -H "Content-Type: application/toml" --data "name = 'bar'
+pass = 'test'" localhost:3000
 ```
 
-### Defining Custom Validator
+### Defining a Custom Validator
 
-All Fiber binders supporting struct validation if you defined validator inside of the config. You can create own validator, or use [go-playground/validator](https://github.com/go-playground/validator), [go-ozzo/ozzo-validation](https://github.com/go-ozzo/ozzo-validation)... Here's an example of simple custom validator:
+All Fiber binders support struct validation if a validator is defined in the configuration. You can create your own validator or use existing ones like [go-playground/validator](https://github.com/go-playground/validator) or [go-ozzo/ozzo-validation](https://github.com/go-ozzo/ozzo-validation). Here's an example of a simple custom validator:
 
 ```go
 type Query struct {
@@ -174,27 +186,29 @@ type Query struct {
 type structValidator struct{}
 
 func (v *structValidator) Engine() any {
-    return ""
+    return nil // Implement if using an external validation engine
 }
 
 func (v *structValidator) ValidateStruct(out any) error {
-    out = reflect.ValueOf(out).Elem().Interface()
-    sq := out.(Query)
+    data := reflect.ValueOf(out).Elem().Interface()
+    query := data.(Query)
 
-    if sq.Name != "john" {
-        return errors.New("you should have entered right name!")
+    if query.Name != "john" {
+        return errors.New("you should have entered the correct name!")
     }
 
     return nil
 }
 
 func main() {
-    app := fiber.New(fiber.Config{StructValidator: &structValidator{}})
+    app := fiber.New(fiber.Config{
+        StructValidator: &structValidator{},
+    })
 
     app.Get("/", func(c fiber.Ctx) error {
         out := new(Query)
         if err := c.Bind().Query(out); err != nil {
-            return err // you should have entered right name!
+            return err // Returns: you should have entered the correct name!
         }
         return c.SendString(out.Name)
     })
@@ -204,5 +218,5 @@ func main() {
 
 // Run tests with the following curl command:
 
-// curl "http://localhost:3000/?name=efe"
+curl "http://localhost:3000/?name=efe"
 ```

ctx.go

@@ -640,7 +640,7 @@ func (c *DefaultCtx) Get(key string, defaultValue ...string) string {
 }
 
 // GetReqHeader returns the HTTP request header specified by filed.
-// This function is generic and can handle differnet headers type values.
+// This function is generic and can handle different headers type values.
 func GetReqHeader[V GenericType](c Ctx, key string, defaultValue ...V) V {
 	var v V
 	return genericParseType[V](c.App().getString(c.Request().Header.Peek(key)), v, defaultValue...)
@@ -1083,7 +1083,7 @@ func (c *DefaultCtx) Params(key string, defaultValue ...string) string {
 }
 
 // Params is used to get the route parameters.
-// This function is generic and can handle differnet route parameters type values.
+// This function is generic and can handle different route parameters type values.
 //
 // Example:
 //
@@ -1860,8 +1860,8 @@ func (c *DefaultCtx) IsFromLocal() bool {
 func (c *DefaultCtx) Bind() *Bind {
 	if c.bind == nil {
 		c.bind = &Bind{
-			ctx:    c,
-			should: true,
+			ctx:            c,
+			dontHandleErrs: true,
 		}
 	}
 	return c.bind