🧹 chore: Refactor internal errors to use sentinel values

bind.go

@@ -1,7 +1,6 @@
 package fiber
 
 import (
-	"errors"
 	"reflect"
 	"slices"
 	"sync"
@@ -41,7 +40,7 @@ type Bind struct {
 func AcquireBind() *Bind {
 	b, ok := bindPool.Get().(*Bind)
 	if !ok {
-		panic(errors.New("failed to type-assert to *Bind"))
+		panic(errBindPoolTypeAssertion)
 	}
 
 	return b

binder/binder.go

@@ -10,8 +10,12 @@ var (
 	ErrSuitableContentNotFound = errors.New("binder: suitable content not found to parse body")
 	ErrMapNotConvertible       = errors.New("binder: map is not convertible to map[string]string or map[string][]string")
 	ErrMapNilDestination       = errors.New("binder: map destination is nil and cannot be initialized")
+	ErrInvalidDestinationValue = errors.New("binder: invalid destination value")
+	ErrUnmatchedBrackets       = errors.New("unmatched brackets")
 )
 
+var errPoolTypeAssertion = errors.New("failed to type-assert to T")
+
 var HeaderBinderPool = sync.Pool{
 	New: func() any {
 		return &HeaderBinding{}
@@ -77,7 +81,7 @@ var MsgPackBinderPool = sync.Pool{
 func GetFromThePool[T any](pool *sync.Pool) T {
 	binder, ok := pool.Get().(T)
 	if !ok {
-		panic(errors.New("failed to type-assert to T"))
+		panic(errPoolTypeAssertion)
 	}
 
 	return binder

binder/mapping.go

@@ -1,7 +1,6 @@
 package binder
 
 import (
-	"errors"
 	"fmt"
 	"maps"
 	"mime/multipart"
@@ -108,7 +107,7 @@ func parseToStruct(aliasTag string, out any, data map[string][]string, files ...
 // thanks to https://github.com/gin-gonic/gin/blob/master/binding/binding.go
 func parseToMap(target reflect.Value, data map[string][]string) error {
 	if !target.IsValid() {
-		return errors.New("binder: invalid destination value")
+		return ErrInvalidDestinationValue
 	}
 
 	if target.Kind() == reflect.Interface && !target.IsNil() {
@@ -179,7 +178,7 @@ func parseParamSquareBrackets(k string) (string, error) {
 		if b == ']' {
 			openBracketsCount--
 			if openBracketsCount < 0 {
-				return "", errors.New("unmatched brackets")
+				return "", ErrUnmatchedBrackets
 			}
 			continue
 		}
@@ -190,7 +189,7 @@ func parseParamSquareBrackets(k string) (string, error) {
 	}
 
 	if openBracketsCount > 0 {
-		return "", errors.New("unmatched brackets")
+		return "", ErrUnmatchedBrackets
 	}
 
 	return bb.String(), nil

binder/mapping_test.go

@@ -1,7 +1,6 @@
 package binder
 
 import (
-	"errors"
 	"mime/multipart"
 	"reflect"
 	"strconv"
@@ -91,17 +90,17 @@ func Test_ParseParamSquareBrackets(t *testing.T) {
 			expected: "foo.bar.baz",
 		},
 		{
-			err:      errors.New("unmatched brackets"),
+			err:      ErrUnmatchedBrackets,
 			input:    "foo[bar",
 			expected: "",
 		},
 		{
-			err:      errors.New("unmatched brackets"),
+			err:      ErrUnmatchedBrackets,
 			input:    "foo[bar][baz",
 			expected: "",
 		},
 		{
-			err:      errors.New("unmatched brackets"),
+			err:      ErrUnmatchedBrackets,
 			input:    "foo]bar[",
 			expected: "",
 		},
@@ -133,8 +132,7 @@ func Test_ParseParamSquareBrackets(t *testing.T) {
 
 			result, err := parseParamSquareBrackets(tt.input)
 			if tt.err != nil {
-				require.Error(t, err)
-				require.EqualError(t, err, tt.err.Error())
+				require.ErrorIs(t, err, tt.err)
 			} else {
 				require.NoError(t, err)
 				require.Equal(t, tt.expected, result)

client/cookiejar.go

@@ -3,7 +3,6 @@ package client
 
 import (
 	"bytes"
-	"errors"
 	"net"
 	"strings"
 	"sync"
@@ -23,7 +22,7 @@ var cookieJarPool = sync.Pool{
 func AcquireCookieJar() *CookieJar {
 	jar, ok := cookieJarPool.Get().(*CookieJar)
 	if !ok {
-		panic(errors.New("failed to type-assert to *CookieJar"))
+		panic(errCookieJarTypeAssertion)
 	}
 
 	return jar

client/core.go

@@ -233,7 +233,7 @@ var responseChanPool = &sync.Pool{
 func acquireResponseChan() chan *Response {
 	ch, ok := responseChanPool.Get().(chan *Response)
 	if !ok {
-		panic(errors.New("failed to type-assert to *Response"))
+		panic(errResponseChanTypeAssertion)
 	}
 	return ch
 }
@@ -258,7 +258,7 @@ var errChanPool = &sync.Pool{
 func acquireErrChan() chan error {
 	ch, ok := errChanPool.Get().(chan error)
 	if !ok {
-		panic(errors.New("failed to type-assert to chan error"))
+		panic(errErrChanTypeAssertion)
 	}
 	return ch
 }

client/errors.go

@@ -0,0 +1,12 @@
+package client
+
+import "errors"
+
+var (
+	errResponseChanTypeAssertion = errors.New("failed to type-assert to *Response")
+	errErrChanTypeAssertion      = errors.New("failed to type-assert to chan error")
+	errRequestTypeAssertion      = errors.New("failed to type-assert to *Request")
+	errFileTypeAssertion         = errors.New("failed to type-assert to *File")
+	errCookieJarTypeAssertion    = errors.New("failed to type-assert to *CookieJar")
+	errSyncPoolBuffer            = errors.New("failed to retrieve buffer from a sync.Pool")
+)

client/hooks.go

@@ -2,7 +2,6 @@ package client
 
 import (
 	"crypto/rand"
-	"errors"
 	"fmt"
 	"io"
 	"mime/multipart"
@@ -265,7 +264,7 @@ func parserRequestBodyFile(req *Request) error {
 	// Add files.
 	fileBuf, ok := fileBufPool.Get().(*[]byte)
 	if !ok {
-		return errors.New("failed to retrieve buffer from a sync.Pool")
+		return errSyncPoolBuffer
 	}
 
 	defer fileBufPool.Put(fileBuf)

client/request.go

@@ -983,7 +983,7 @@ var requestPool = &sync.Pool{
 func AcquireRequest() *Request {
 	req, ok := requestPool.Get().(*Request)
 	if !ok {
-		panic(errors.New("failed to type-assert to *Request"))
+		panic(errRequestTypeAssertion)
 	}
 	return req
 }
@@ -1034,7 +1034,7 @@ func AcquireFile(setter ...SetFileFunc) *File {
 	if fv != nil {
 		f, ok := fv.(*File)
 		if !ok {
-			panic(errors.New("failed to type-assert to *File"))
+			panic(errFileTypeAssertion)
 		}
 		for _, v := range setter {
 			v(f)

ctx_interface.go

@@ -4,11 +4,7 @@
 
 package fiber
 
-import (
-	"errors"
-
-	"github.com/valyala/fasthttp"
-)
+import "github.com/valyala/fasthttp"
 
 // CustomCtx extends Ctx with the additional methods required by Fiber's
 // internals and middleware helpers.
@@ -53,7 +49,7 @@
 	ctx, ok := app.pool.Get().(CustomCtx)
 
 	if !ok {
-		panic(errors.New("failed to type-assert to CustomCtx"))
+		panic(errCustomCtxTypeAssertion)
 	}
 
 	if app.hasCustomCtx {

errors_internal.go

@@ -0,0 +1,12 @@
+package fiber
+
+import "errors"
+
+var (
+	errBindPoolTypeAssertion  = errors.New("failed to type-assert to *Bind")
+	errCustomCtxTypeAssertion = errors.New("failed to type-assert to CustomCtx")
+	errTLSConfigTypeAssertion = errors.New("failed to type-assert to *tls.Config")
+	errInvalidEscapeSequence  = errors.New("invalid escape sequence")
+	errTCPAddrTypeAssertion   = errors.New("failed to type-assert to *net.TCPAddr")
+	errRedirectTypeAssertion  = errors.New("failed to type-assert to *Redirect")
+)

helpers.go

@@ -68,7 +68,7 @@ func getTLSConfig(ln net.Listener) *tls.Config {
 				// Cast value to *tls.Config
 				c, ok := reflect.TypeAssert[*tls.Config](elem)
 				if !ok {
-					panic(errors.New("failed to type-assert to *tls.Config"))
+					panic(errTLSConfigTypeAssertion)
 				}
 				return c
 			}
@@ -402,15 +402,15 @@ func unescapeHeaderValue(v []byte) ([]byte, error) {
 		if c == '\\' {
 			// invalid escape at end of string
 			if i == len(v)-1 {
-				return nil, errors.New("invalid escape sequence")
+				return nil, errInvalidEscapeSequence
 			}
 			escaping = true
 			continue
 		}
 		res = append(res, c)
 	}
 	if escaping {
-		return nil, errors.New("invalid escape sequence")
+		return nil, errInvalidEscapeSequence
 	}
 	return res, nil
 }

internal/tlstest/tls.go

@@ -15,6 +15,8 @@ import (
 	"time"
 )
 
+var errAppendCACert = errors.New("append CA cert to cert pool")
+
 // GetTLSConfigs generates TLS configurations for a test server and client that
 // trust each other using an in-memory certificate authority.
 func GetTLSConfigs() (serverTLSConf, clientTLSConf *tls.Config, err error) { //nolint:nonamedreturns // gocritic unnamedResult prefers naming server and client TLS configurations along with the error
@@ -123,7 +125,7 @@ func GetTLSConfigs() (serverTLSConf, clientTLSConf *tls.Config, err error) { //n
 
 	certPool := x509.NewCertPool()
 	if ok := certPool.AppendCertsFromPEM(caPEM.Bytes()); !ok {
-		return nil, nil, errors.New("append CA cert to cert pool")
+		return nil, nil, errAppendCACert
 	}
 	clientTLSConf = &tls.Config{
 		RootCAs:    certPool,

middleware/adaptor/adaptor.go

@@ -37,6 +37,11 @@ var bufferPool = sync.Pool{
 	},
 }
 
+var (
+	ErrRemoteAddrEmpty   = errors.New("remote address cannot be empty")
+	ErrRemoteAddrTooLong = errors.New("remote address too long")
+)
+
 // HTTPHandlerFunc wraps net/http handler func to fiber handler
 func HTTPHandlerFunc(h http.HandlerFunc) fiber.Handler {
 	return HTTPHandler(h)
@@ -178,7 +183,7 @@ func resolveRemoteAddr(remoteAddr string, localAddr any) (net.Addr, error) {
 
 	// Validate input to prevent malformed addresses
 	if remoteAddr == "" {
-		return nil, errors.New("remote address cannot be empty")
+		return nil, ErrRemoteAddrEmpty
 	}
 
 	resolved, err := net.ResolveTCPAddr("tcp", remoteAddr)
@@ -189,7 +194,7 @@ func resolveRemoteAddr(remoteAddr string, localAddr any) (net.Addr, error) {
 	var addrErr *net.AddrError
 	if errors.As(err, &addrErr) && addrErr.Err == "missing port in address" {
 		if len(remoteAddr) > 253 { // Max hostname length
-			return nil, errors.New("remote address too long")
+			return nil, ErrRemoteAddrTooLong
 		}
 		remoteAddr = net.JoinHostPort(remoteAddr, "80")
 		resolved, err2 := net.ResolveTCPAddr("tcp", remoteAddr)

middleware/adaptor/adaptor_test.go

@@ -1121,6 +1121,7 @@ func Test_resolveRemoteAddr(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
+		expectedErr   error
 		localAddr     any
 		name          string
 		remoteAddr    string
@@ -1164,13 +1165,14 @@ func Test_resolveRemoteAddr(t *testing.T) {
 			remoteAddr:  "",
 			localAddr:   nil,
 			expectError: true,
+			expectedErr: ErrRemoteAddrEmpty,
 		},
 		{
-			name:          "too long address - should fail",
-			remoteAddr:    strings.Repeat("a", 254),
-			localAddr:     nil,
-			expectError:   true,
-			errorContains: "remote address too long",
+			name:        "too long address - should fail",
+			remoteAddr:  strings.Repeat("a", 254),
+			localAddr:   nil,
+			expectError: true,
+			expectedErr: ErrRemoteAddrTooLong,
 		},
 	}
 
@@ -1179,8 +1181,12 @@ func Test_resolveRemoteAddr(t *testing.T) {
 			t.Parallel()
 			addr, err := resolveRemoteAddr(tt.remoteAddr, tt.localAddr)
 
-			if tt.expectError {
+			expectError := tt.expectedErr != nil || tt.errorContains != ""
+			if expectError {
 				require.Error(t, err)
+				if tt.expectedErr != nil {
+					require.ErrorIs(t, err, tt.expectedErr)
+				}
 				if tt.errorContains != "" {
 					require.Contains(t, err.Error(), tt.errorContains)
 				}

middleware/basicauth/config.go

@@ -15,6 +15,8 @@ import (
 	"golang.org/x/crypto/bcrypt"
 )
 
+var ErrInvalidSHA256PasswordLength = errors.New("decode SHA256 password: invalid length")
+
 // Config defines the config for middleware.
 type Config struct {
 	// Next defines a function to skip this middleware when returned true.
@@ -188,7 +190,7 @@ func parseHashedPassword(h string) (func(string) bool, error) {
 				return nil, fmt.Errorf("decode SHA256 password: %w", err)
 			}
 			if len(b) != sha256.Size {
-				return nil, errors.New("decode SHA256 password: invalid length")
+				return nil, ErrInvalidSHA256PasswordLength
 			}
 		}
 		return func(p string) bool {

middleware/encryptcookie/utils.go

@@ -11,7 +11,10 @@ import (
 	"slices"
 )
 
-var ErrInvalidKeyLength = errors.New("encryption key must be 16, 24, or 32 bytes")
+var (
+	ErrInvalidKeyLength      = errors.New("encryption key must be 16, 24, or 32 bytes")
+	ErrInvalidEncryptedValue = errors.New("encrypted value is not valid")
+)
 
 // decodeKey decodes the provided base64-encoded key and validates its length.
 // It returns the decoded key bytes or an error when invalid.
@@ -86,7 +89,7 @@ func DecryptCookie(name, value, key string) (string, error) {
 	nonceSize := gcm.NonceSize()
 
 	if len(enc) < nonceSize {
-		return "", errors.New("encrypted value is not valid")
+		return "", ErrInvalidEncryptedValue
 	}
 
 	nonce, ciphertext := enc[:nonceSize], enc[nonceSize:]