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 5 package scanner
6 7 import (
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 type Error struct {
19 Pos token.Position
20 Msg []byte
21 }
22 23 // Error implements the error interface.
24 func (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.
35 type ErrorList []*Error
36 37 // Add adds an [Error] with given position and error message to an [ErrorList].
38 func (p *ErrorList) Add(pos token.Position, msg []byte) {
39 *p = append(*p, &Error{pos, msg})
40 }
41 42 // Reset resets an [ErrorList] to no errors.
43 func (p *ErrorList) Reset() { *p = (*p)[0:0] }
44 45 // [ErrorList] implements the sort Interface.
46 func (p ErrorList) Len() int { return len(p) }
47 func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
48 49 func (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.
70 func (p ErrorList) Sort() {
71 sort.Sort(p)
72 }
73 74 // RemoveMultiples sorts an [ErrorList] and removes all but the first error per line.
75 func (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.
90 func (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.
102 func (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.
112 func 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