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