nilnil

尼尼尔

检查没有同时返回nil错误和无效的值。

安装和用法

 $ go install github.com/Antonboom/nilnil@latest
$ nilnil ./...

动机

return nil, nil并不是惯用的。开发人员被用来以下事实：如果没有错误，则返回值是有效的，并且可以在没有其他检查的情况下使用：

 user , err := getUser ()
if err != nil {
    return err
}
if user != nil { // Ambiguous!
    // Use user.
}

充其量会导致评论

 // ...
// If this compilation unit has no line table, it returns nil, nil.
func ( d * Data ) LineReader ( cu * Entry ) ( * LineReader , error ) {

这不是真正的约束。在最坏的情况下，这种代码可能会导致恐慌。

使用Sentinel错误重写上面的示例：

 user , err := getUser ()
if errors . Is ( err , errUserNotFound ) {
    // Do something and return.
}
if err != nil {
    return err
}

// Use user.

相反的情况

有时人们将相反的情况（同时返回非NIL错误和有效的值返回有效的值）也是反模式，因为它可能导致难以找到的错误。

例如，此Kubernetes代码

 func ( fh * fakeHistory ) UpdateControllerRevision ( revision * apps. ControllerRevision , newRevision int64 ) ( * apps. ControllerRevision , error ) {
    clone := revision . DeepCopy ()
    clone . Revision = newRevision
    return clone , fh . indexer . Update ( clone )
}

可以用如下重写

 func ( fh * fakeHistory ) UpdateControllerRevision ( revision * apps. ControllerRevision , newRevision int64 ) ( * apps. ControllerRevision , error ) {
    clone := revision . DeepCopy ()
    clone . Revision = newRevision
    if err := fh . indexer . Update ( clone ); err != nil {
        return nil , fmt . Errorf ( "update index: %w" , err )
    }
    return clone , nil
}

如果我认为这是胡扯怎么办？

我知道每种情况都需要单独分析，但是我希望林格能使您重新思考 - 是否有必要使用模棱两可的API ，还是使用Sentinel错误更好地进行操作？

在任何情况下，您都无法启用衬里。

配置

CLI

$ nilnil --checked-types chan,func,iface,map,ptr,uintptr,unsafeptr ./...
$ nilnil --detect-opposite ./...
$ nilnil --detect-opposite --checked-types ptr ./..

Golangci-lint

https://golangci-lint.run/usage/linters/#nilnil

 linters-settings :
  nilnil :
    # In addition, detect opposite situation (simultaneous return of non-nil error and valid value).
    # Default: false
    detect-opposite : true
    # List of return types to check.
    # Default: ["chan", "func", "iface", "map", "ptr", "uintptr", "unsafeptr"]
    checked-types :
      - chan
      - func
      - iface
      - map
      - ptr
      - uintptr
      - unsafeptr 

例子

来自加密/TLS的Parsepublickey

 // BEFORE

func parsePublicKey ( algo PublicKeyAlgorithm , keyData * publicKeyInfo ) ( interface {}, error ) {
    der := cryptobyte . String ( keyData . PublicKey . RightAlign ())
    switch algo {
    case RSA :
        // ...
        return pub , nil
    case ECDSA :
        // ...
        return pub , nil
    case Ed25519 :
        // ...
        return ed25519 . PublicKey ( der ), nil
    case DSA :
        // ...
        return pub , nil
    default :
        return nil , nil
    }
}

// AFTER

var errUnknownPublicKeyAlgo = errors . New ( "unknown public key algo" )

func parsePublicKey ( algo PublicKeyAlgorithm , keyData * publicKeyInfo ) ( interface {}, error ) {
    der := cryptobyte . String ( keyData . PublicKey . RightAlign ())
    switch algo {
    case RSA :
        // ...
        return pub , nil
    case ECDSA :
        // ...
        return pub , nil
    case Ed25519 :
        // ...
        return ed25519 . PublicKey ( der ), nil
    case DSA :
        // ...
        return pub , nil
    default :
        return nil , fmt . Errorf ( "%w: %v" , errUnknownPublicKeyAlgo , algo )
    }
}

NET/HTTP的HTTP2ClientConnReadloop

 // BEFORE

// As a special case, handleResponse may return (nil, nil) to skip the frame.
func ( rl * http2clientConnReadLoop ) handleResponse ( /* ... */ ) ( * Response , error ) {
    if statusCode >= 100 && statusCode <= 199 {
        return nil , nil
    }
}

// ...
res , err := rl . handleResponse ( cs , f )
if err != nil {
	return err
}
if res == nil {
    // (nil, nil) special case. See handleResponse docs.
    return nil
}

// AFTER

var errNeedSkipFrame = errors . New ( "need skip frame" )

// As a special case, handleResponse may return errNeedSkipFrame to skip the frame.
func ( rl * http2clientConnReadLoop ) handleResponse ( /* ... */ ) ( * Response , error ) {
    if statusCode >= 100 && statusCode <= 199 {
        return nil , errNeedSkipFrame
    }
}

// ...
res , err := rl . handleResponse ( cs , f )
if errors . Is ( err , errNeedSkipFrame ) {
    return nil
}
if err != nil {
    return err
}

未实施

 // BEFORE

func ( s * Service ) StartStream ( ctx context. Context ) ( * Stream , error ) {
    return nil , nil
}

// AFTER

func ( s * Service ) StartStream ( ctx context. Context ) ( * Stream , error ) {
    return nil , errors . New ( "not implemented" )
}

尼尔安全类型

 package ratelimiter

type RateLimiter struct {
    // ...
}

func New () ( * RateLimiter , error ) {
    // It's OK, RateLimiter is nil-safe.
    // But it's better not to do it anyway.
    return nil , nil
}

func ( r * RateLimiter ) Allow () bool {
    if r == nil {
        return true
    }
    return r . allow ()
}

假设

• Linter仅使用两个返回参数检查函数，其中最后一个实现了error 。
• 检查下一类型：
  • 指针（包括uinptr和unsafe.Pointer ），功能和接口（ panic: invalid memory address or nil pointer dereference ）；
  • 地图（ panic: assignment to entry in nil map ）；
  • 频道（ fatal error: all goroutines are asleep - deadlock! ）
• 仅支持明确的return nil, nil 。

检查GO 1.22.2源代码

单击以展开

$ cd $GOROOT /src
$ nilnil ./... 2>&1 | grep -v " _test.go "  
/usr/local/go/src/internal/bisect/bisect.go:196:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/fd_unix.go:71:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/fd_unix.go:79:4: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/fd_unix.go:156:4: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/iprawsock_posix.go:36:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/tcpsock_posix.go:38:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/udpsock_posix.go:37:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/unixsock_posix.go:92:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/crypto/tls/key_agreement.go:46:2: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/crypto/tls/ticket.go:355:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/crypto/tls/ticket.go:359:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/driver/types.go:157:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/driver/types.go:232:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/driver/types.go:263:4: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/convert.go:548:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:205:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:231:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:257:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:284:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:311:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:337:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:363:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:389:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/database/sql/sql.go:422:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/debug/dwarf/entry.go:884:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/debug/dwarf/line.go:146:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/debug/dwarf/line.go:153:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/debug/dwarf/typeunit.go:138:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/debug/pe/file.go:470:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/http/h2_bundle.go:9530:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/http/transfer.go:765:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/http/transfer.go:775:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/http/transfer.go:798:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/go/build/build.go:1442:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/go/build/build.go:1453:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/go/build/build.go:1457:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/go/build/build.go:1491:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/go/internal/gccgoimporter/ar.go:125:3: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/image/jpeg/reader.go:622:5: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/image/png/reader.go:434:4: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/internal/profile/legacy_profile.go:1089:4: return both a ` nil ` error and an invalid value: use a sentinel error instead
/usr/local/go/src/net/internal/socktest/switch.go:142:3: return both a ` nil ` error and an invalid value: use a sentinel error instead