1// Copyright 2009 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 5package scanner 6 7import ( 8 "fmt" 9 "go/token" 10 "io" 11 "sort" 12) 13 14// In an [ErrorList], an error is represented by an *Error. 15// The position Pos, if valid, points to the beginning of 16// the offending token, and the error condition is described 17// by Msg. 18type Error struct { 19 Pos token.Position 20 Msg string 21} 22 23// Error implements the error interface. 24func (e Error) Error() string { 25 if e.Pos.Filename != "" || e.Pos.IsValid() { 26 // don't print "<unknown position>" 27 // TODO(gri) reconsider the semantics of Position.IsValid 28 return e.Pos.String() + ": " + e.Msg 29 } 30 return e.Msg 31} 32 33// ErrorList is a list of *Errors. 34// The zero value for an ErrorList is an empty ErrorList ready to use. 35type ErrorList []*Error 36 37// Add adds an [Error] with given position and error message to an [ErrorList]. 38func (p *ErrorList) Add(pos token.Position, msg string) { 39 *p = append(*p, &Error{pos, msg}) 40} 41 42// Reset resets an [ErrorList] to no errors. 43func (p *ErrorList) Reset() { *p = (*p)[0:0] } 44 45// [ErrorList] implements the sort Interface. 46func (p ErrorList) Len() int { return len(p) } 47func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] } 48 49func (p ErrorList) Less(i, j int) bool { 50 e := &p[i].Pos 51 f := &p[j].Pos 52 // Note that it is not sufficient to simply compare file offsets because 53 // the offsets do not reflect modified line information (through //line 54 // comments). 55 if e.Filename != f.Filename { 56 return e.Filename < f.Filename 57 } 58 if e.Line != f.Line { 59 return e.Line < f.Line 60 } 61 if e.Column != f.Column { 62 return e.Column < f.Column 63 } 64 return p[i].Msg < p[j].Msg 65} 66 67// Sort sorts an [ErrorList]. *[Error] entries are sorted by position, 68// other errors are sorted by error message, and before any *[Error] 69// entry. 70func (p ErrorList) Sort() { 71 sort.Sort(p) 72} 73 74// RemoveMultiples sorts an [ErrorList] and removes all but the first error per line. 75func (p *ErrorList) RemoveMultiples() { 76 sort.Sort(p) 77 var last token.Position // initial last.Line is != any legal error line 78 i := 0 79 for _, e := range *p { 80 if e.Pos.Filename != last.Filename || e.Pos.Line != last.Line { 81 last = e.Pos 82 (*p)[i] = e 83 i++ 84 } 85 } 86 *p = (*p)[0:i] 87} 88 89// An [ErrorList] implements the error interface. 90func (p ErrorList) Error() string { 91 switch len(p) { 92 case 0: 93 return "no errors" 94 case 1: 95 return p[0].Error() 96 } 97 return fmt.Sprintf("%s (and %d more errors)", p[0], len(p)-1) 98} 99 100// Err returns an error equivalent to this error list. 101// If the list is empty, Err returns nil. 102func (p ErrorList) Err() error { 103 if len(p) == 0 { 104 return nil 105 } 106 return p 107} 108 109// PrintError is a utility function that prints a list of errors to w, 110// one error per line, if the err parameter is an [ErrorList]. Otherwise 111// it prints the err string. 112func PrintError(w io.Writer, err error) { 113 if list, ok := err.(ErrorList); ok { 114 for _, e := range list { 115 fmt.Fprintf(w, "%s\n", e) 116 } 117 } else if err != nil { 118 fmt.Fprintf(w, "%s\n", err) 119 } 120} 121