errors.go

Documentation: fmt

		 1  // Copyright 2018 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package fmt
		 6  
		 7  import "errors"
		 8  
		 9  // Errorf formats according to a format specifier and returns the string as a
		10  // value that satisfies error.
		11  //
		12  // If the format specifier includes a %w verb with an error operand,
		13  // the returned error will implement an Unwrap method returning the operand. It is
		14  // invalid to include more than one %w verb or to supply it with an operand
		15  // that does not implement the error interface. The %w verb is otherwise
		16  // a synonym for %v.
		17  func Errorf(format string, a ...interface{}) error {
		18  	p := newPrinter()
		19  	p.wrapErrs = true
		20  	p.doPrintf(format, a)
		21  	s := string(p.buf)
		22  	var err error
		23  	if p.wrappedErr == nil {
		24  		err = errors.New(s)
		25  	} else {
		26  		err = &wrapError{s, p.wrappedErr}
		27  	}
		28  	p.free()
		29  	return err
		30  }
		31  
		32  type wrapError struct {
		33  	msg string
		34  	err error
		35  }
		36  
		37  func (e *wrapError) Error() string {
		38  	return e.msg
		39  }
		40  
		41  func (e *wrapError) Unwrap() error {
		42  	return e.err
		43  }
		44
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