lancet/docs/en/api/packages/xerror.md

# Xerror

Package xerror implements helpers for errors.

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## Source:

-   [https://github.com/duke-git/lancet/blob/main/xerror/xerror.go](https://github.com/duke-git/lancet/blob/main/xerror/xerror.go)

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## Usage:

```go
import (
    "github.com/duke-git/lancet/v2/xerror"
)
```

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## Index

-   [New](#New)
-   [Wrap](#Wrap)
-   [Unwrap](#Unwrap)
-   [XError_Wrap](#XError_Wrap)
-   [XError_Unwrap](#XError_Unwrap)
-   [XError_With](#XError_With)
-   [XError_Is](#XError_Is)
-   [XError_Id](#XError_Id)
-   [XError_Values](#XError_Values)
-   [XError_StackTrace](#XError_StackTrace)
-   [XError_Info](#XError_Info)
-   [XError_Error](#XError_Error)
-   [TryUnwrap](#TryUnwrap)
-   [TryCatch](#TryCatch)

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## Documentation

### <span id="New">New</span>

<p>Creates a new XError pointer instance with message.</p>

<b>Signature:</b>

```go
type XError struct {
    id      string
    message string
    stack   *stack
    cause   error
    values  map[string]any
}

func New(format string, args ...any) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/w4oWZts7q7f)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("error")
    fmt.Println(err.Error())

    // Output:
    // error
}
```

### <span id="Wrap">Wrap</span>

<p>Creates a new XError pointer instance based on error object, and add message.</p>

<b>Signature:</b>

```go
func Wrap(cause error, message ...any) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/5385qT2dCi4)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("wrong password")
    wrapErr := xerror.Wrap(err, "error")

    fmt.Println(wrapErr.Error())

    // Output:
    // error: wrong password
}
```

### <span id="Unwrap">Unwrap</span>

<p>Returns unwrapped XError from err by errors.As. If no XError, returns nil.</p>

<b>Signature:</b>

```go
func Unwrap(err error) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/LKMLep723tu)</span></b>

```go
package main

import (
    "fmt"
    "github.com/pkg/errors"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err1 := xerror.New("error").With("level", "high")
    wrapErr := errors.Wrap(err1, "oops")

    err := xerror.Unwrap(wrapErr)

    values := err.Values()
    fmt.Println(values["level"])

    // Output:
    // high
}
```

### <span id="XError_Wrap">XError_Wrap</span>

<p>Creates a new XError and copy message and id to new one.</p>

<b>Signature:</b>

```go
func (e *XError) Wrap(cause error) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/RpjJ5u5sc97)</span></b>

```go
package main

import (
    "fmt"
    "errors"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err1 := xerror.New("error").With("level", "high")
    err2 := err1.Wrap(errors.New("invalid username"))

    fmt.Println(err2.Error())

    // Output:
    // error: invalid username
}
```

### <span id="XError_Unwrap">XError_Unwrap</span>

<p>Compatible with github.com/pkg/errors.</p>

<b>Signature:</b>

```go
func (e *XError) Unwrap() error
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/VUXJ8BST4c6)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err1 := xerror.New("error").With("level", "high")
    err2 := err1.Wrap(errors.New("invalid username"))

    err := err2.Unwrap()

    fmt.Println(err.Error())

    // Output:
    // invalid username
}
```

### <span id="XError_With">XError_With</span>

<p>Adds key and value related to the XError object.</p>

<b>Signature:</b>

```go
func (e *XError) With(key string, value any) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/ow8UISXX_Dp)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("error").With("level", "high")

    errLevel := err.Values()["level"]

    fmt.Println(errLevel)

    // Output:
    // high
}
```

### <span id="XError_Id">XError_Id</span>

<p>Sets XError object id to check equality in XError.Is.</p>

<b>Signature:</b>

```go
func (e *XError) Id(id string) *XError
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/X6HBlsy58U9)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err1 := xerror.New("error").Id("e001")
    err2 := xerror.New("error").Id("e001")
    err3 := xerror.New("error").Id("e003")

    equal := err1.Is(err2)
    notEqual := err1.Is(err3)

    fmt.Println(equal)
    fmt.Println(notEqual)

    // Output:
    // true
    // false
}
```

### <span id="XError_Is">XError_Is</span>

<p>Checks if target error is XError and Error.id of two errors are matched.</p>

<b>Signature:</b>

```go
func (e *XError) Is(target error) bool
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/X6HBlsy58U9)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err1 := xerror.New("error").Id("e001")
    err2 := xerror.New("error").Id("e001")
    err3 := xerror.New("error").Id("e003")

    equal := err1.Is(err2)
    notEqual := err1.Is(err3)

    fmt.Println(equal)
    fmt.Println(notEqual)

    // Output:
    // true
    // false
}
```

### <span id="XError_Values">XError_Values</span>

<p>Returns map of key and value that is set by With. All wrapped xerror.XError key and values will be merged. Key and values of wrapped error is overwritten by upper xerror.XError.</p>

<b>Signature:</b>

```go
func (e *XError) Values() map[string]any
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/ow8UISXX_Dp)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("error").With("level", "high")

    errLevel := err.Values()["level"]

    fmt.Println(errLevel)

    // Output:
    // high
}
```


### <span id="XError_StackTrace">XError_StackTrace</span>

<p>Returns stack trace which is compatible with pkg/errors.</p>

<b>Signature:</b>

```go
func (e *XError) StackTrace() StackTrace
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/6FAvSQpa7pc)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("error")

    stacks := err.Stacks()

    fmt.Println(stacks[0].Func)
    fmt.Println(stacks[0].Line)

    containFile := strings.Contains(stacks[0].File, "xxx.go")
    fmt.Println(containFile)
}
```


### <span id="XError_Info">XError_Info</span>

<p>Returns information of xerror, which can be printed.</p>

<b>Signature:</b>

```go
func (e *XError) Info() *errInfo
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/1ZX0ME1F-Jb)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    cause := errors.New("error")
    err := xerror.Wrap(cause, "invalid username").Id("e001").With("level", "high")

    errInfo := err.Info()

    fmt.Println(errInfo.Id)
    fmt.Println(errInfo.Cause)
    fmt.Println(errInfo.Values["level"])
    fmt.Println(errInfo.Message)

    // Output:
    // e001
    // error
    // high
    // invalid username
}
```


### <span id="XError_Error">XError_Error</span>

<p>Error implements standard error interface.</p>

<b>Signature:</b>

```go
func (e *XError) Error() string
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/w4oWZts7q7f)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    err := xerror.New("error")
    fmt.Println(err.Error())

    // Output:
    // error
}
```
### <span id="TryUnwrap">TryUnwrap</span>

<p>TryUnwrap if err is nil then it returns a valid value. If err is not nil, Unwrap panics with err.</p>

<b>Signature:</b>

```go
func TryUnwrap[T any](val T, err error) T
```

<b>Example:<span style="float:right;display:inline-block;">[Run](https://go.dev/play/p/acyZVkNZEeW)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    result1 := xerror.TryUnwrap(strconv.Atoi("42"))
    fmt.Println(result1)

    _, err := strconv.Atoi("4o2")
    defer func() {
        v := recover()
        result2 := reflect.DeepEqual(err.Error(), v.(*strconv.NumError).Error())
        fmt.Println(result2)
    }()

    xerror.TryUnwrap(strconv.Atoi("4o2"))

    // Output:
    // 42
    // true
}
```

### <span id="TryCatch">TryCatch</span>

<p>Simple simulation of Java-style try-catch. It does not align with Go's error-handling philosophy. It is recommended to use it with caution.</p>

<b>Signature:</b>

```go
func NewTryCatch(ctx context.Context) *TryCatch

func (tc *TryCatch) Try(tryFunc func(ctx context.Context) error) *TryCatch

func (tc *TryCatch) Catch(catchFunc func(ctx context.Context, err error)) *TryCatch

func (tc *TryCatch) Finally(finallyFunc func(ctx context.Context)) *TryCatch

func (tc *TryCatch) Do()
```

<b>Example:<span style="float:right;display:inline-block;">[Run](todo)</span></b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/xerror"
)

func main() {
    calledFinally := false
    calledCatch := false

    tc := xerror.NewTryCatch(context.Background())

    tc.Try(func(ctx context.Context) error {
        return errors.New("error message    ")
    }).Catch(func(ctx context.Context, err error) {
        calledCatch = true
        // Error in try block at /path/xxx.go:{line_number} - Cause: error message
		// fmt.Println(err.Error())
    }).Finally(func(ctx context.Context) {
        calledFinally = true
    }).Do()

    fmt.Println(calledCatch)
    fmt.Println(calledFinally)

    // Output:
    // true
    // true
}
```