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. 18// 19type Error struct { 20 Pos token.Position 21 Msg string 22} 23 24// Error implements the error interface. 25func (e Error) Error() string { 26 if e.Pos.Filename != "" || e.Pos.IsValid() { 27 // don't print "<unknown position>" 28 // TODO(gri) reconsider the semantics of Position.IsValid 29 return e.Pos.String() + ": " + e.Msg 30 } 31 return e.Msg 32} 33 34// ErrorList is a list of *Errors. 35// The zero value for an ErrorList is an empty ErrorList ready to use. 36// 37type ErrorList []*Error 38 39// Add adds an Error with given position and error message to an ErrorList. 40func (p *ErrorList) Add(pos token.Position, msg string) { 41 *p = append(*p, &Error{pos, msg}) 42} 43 44// Reset resets an ErrorList to no errors. 45func (p *ErrorList) Reset() { *p = (*p)[0:0] } 46 47// ErrorList implements the sort Interface. 48func (p ErrorList) Len() int { return len(p) } 49func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] } 50 51func (p ErrorList) Less(i, j int) bool { 52 e := &p[i].Pos 53 f := &p[j].Pos 54 // Note that it is not sufficient to simply compare file offsets because 55 // the offsets do not reflect modified line information (through //line 56 // comments). 57 if e.Filename != f.Filename { 58 return e.Filename < f.Filename 59 } 60 if e.Line != f.Line { 61 return e.Line < f.Line 62 } 63 if e.Column != f.Column { 64 return e.Column < f.Column 65 } 66 return p[i].Msg < p[j].Msg 67} 68 69// Sort sorts an ErrorList. *Error entries are sorted by position, 70// other errors are sorted by error message, and before any *Error 71// entry. 72// 73func (p ErrorList) Sort() { 74 sort.Sort(p) 75} 76 77// RemoveMultiples sorts an ErrorList and removes all but the first error per line. 78func (p *ErrorList) RemoveMultiples() { 79 sort.Sort(p) 80 var last token.Position // initial last.Line is != any legal error line 81 i := 0 82 for _, e := range *p { 83 if e.Pos.Filename != last.Filename || e.Pos.Line != last.Line { 84 last = e.Pos 85 (*p)[i] = e 86 i++ 87 } 88 } 89 *p = (*p)[0:i] 90} 91 92// An ErrorList implements the error interface. 93func (p ErrorList) Error() string { 94 switch len(p) { 95 case 0: 96 return "no errors" 97 case 1: 98 return p[0].Error() 99 } 100 return fmt.Sprintf("%s (and %d more errors)", p[0], len(p)-1) 101} 102 103// Err returns an error equivalent to this error list. 104// If the list is empty, Err returns nil. 105func (p ErrorList) Err() error { 106 if len(p) == 0 { 107 return nil 108 } 109 return p 110} 111 112// PrintError is a utility function that prints a list of errors to w, 113// one error per line, if the err parameter is an ErrorList. Otherwise 114// it prints the err string. 115// 116func PrintError(w io.Writer, err error) { 117 if list, ok := err.(ErrorList); ok { 118 for _, e := range list { 119 fmt.Fprintf(w, "%s\n", e) 120 } 121 } else if err != nil { 122 fmt.Fprintf(w, "%s\n", err) 123 } 124} 125