/
stdmethods.go
187 lines (164 loc) · 6.51 KB
/
stdmethods.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package stdmethods defines an Analyzer that checks for misspellings
// in the signatures of methods similar to well-known interfaces.
package stdmethods
import (
"go/ast"
"go/types"
"strings"
"github.com/april1989/origin-go-tools/go/analysis"
"github.com/april1989/origin-go-tools/go/analysis/passes/inspect"
"github.com/april1989/origin-go-tools/go/ast/inspector"
)
const Doc = `check signature of methods of well-known interfaces
Sometimes a type may be intended to satisfy an interface but may fail to
do so because of a mistake in its method signature.
For example, the result of this WriteTo method should be (int64, error),
not error, to satisfy io.WriterTo:
type myWriterTo struct{...}
func (myWriterTo) WriteTo(w io.Writer) error { ... }
This check ensures that each method whose name matches one of several
well-known interface methods from the standard library has the correct
signature for that interface.
Checked method names include:
Format GobEncode GobDecode MarshalJSON MarshalXML
Peek ReadByte ReadFrom ReadRune Scan Seek
UnmarshalJSON UnreadByte UnreadRune WriteByte
WriteTo
`
var Analyzer = &analysis.Analyzer{
Name: "stdmethods",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
}
// canonicalMethods lists the input and output types for Go methods
// that are checked using dynamic interface checks. Because the
// checks are dynamic, such methods would not cause a compile error
// if they have the wrong signature: instead the dynamic check would
// fail, sometimes mysteriously. If a method is found with a name listed
// here but not the input/output types listed here, vet complains.
//
// A few of the canonical methods have very common names.
// For example, a type might implement a Scan method that
// has nothing to do with fmt.Scanner, but we still want to check
// the methods that are intended to implement fmt.Scanner.
// To do that, the arguments that have a = prefix are treated as
// signals that the canonical meaning is intended: if a Scan
// method doesn't have a fmt.ScanState as its first argument,
// we let it go. But if it does have a fmt.ScanState, then the
// rest has to match.
var canonicalMethods = map[string]struct{ args, results []string }{
// "Flush": {{}, {"error"}}, // http.Flusher and jpeg.writer conflict
"Format": {[]string{"=fmt.State", "rune"}, []string{}}, // fmt.Formatter
"GobDecode": {[]string{"[]byte"}, []string{"error"}}, // gob.GobDecoder
"GobEncode": {[]string{}, []string{"[]byte", "error"}}, // gob.GobEncoder
"MarshalJSON": {[]string{}, []string{"[]byte", "error"}}, // json.Marshaler
"MarshalXML": {[]string{"*xml.Encoder", "xml.StartElement"}, []string{"error"}}, // xml.Marshaler
"ReadByte": {[]string{}, []string{"byte", "error"}}, // io.ByteReader
"ReadFrom": {[]string{"=io.Reader"}, []string{"int64", "error"}}, // io.ReaderFrom
"ReadRune": {[]string{}, []string{"rune", "int", "error"}}, // io.RuneReader
"Scan": {[]string{"=fmt.ScanState", "rune"}, []string{"error"}}, // fmt.Scanner
"Seek": {[]string{"=int64", "int"}, []string{"int64", "error"}}, // io.Seeker
"UnmarshalJSON": {[]string{"[]byte"}, []string{"error"}}, // json.Unmarshaler
"UnmarshalXML": {[]string{"*xml.Decoder", "xml.StartElement"}, []string{"error"}}, // xml.Unmarshaler
"UnreadByte": {[]string{}, []string{"error"}},
"UnreadRune": {[]string{}, []string{"error"}},
"WriteByte": {[]string{"byte"}, []string{"error"}}, // jpeg.writer (matching bufio.Writer)
"WriteTo": {[]string{"=io.Writer"}, []string{"int64", "error"}}, // io.WriterTo
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.FuncDecl)(nil),
(*ast.InterfaceType)(nil),
}
inspect.Preorder(nodeFilter, func(n ast.Node) {
switch n := n.(type) {
case *ast.FuncDecl:
if n.Recv != nil {
canonicalMethod(pass, n.Name)
}
case *ast.InterfaceType:
for _, field := range n.Methods.List {
for _, id := range field.Names {
canonicalMethod(pass, id)
}
}
}
})
return nil, nil
}
func canonicalMethod(pass *analysis.Pass, id *ast.Ident) {
// Expected input/output.
expect, ok := canonicalMethods[id.Name]
if !ok {
return
}
// Actual input/output
sign := pass.TypesInfo.Defs[id].Type().(*types.Signature)
args := sign.Params()
results := sign.Results()
// Special case: WriteTo with more than one argument,
// not trying at all to implement io.WriterTo,
// comes up often enough to skip.
if id.Name == "WriteTo" && args.Len() > 1 {
return
}
// Do the =s (if any) all match?
if !matchParams(pass, expect.args, args, "=") || !matchParams(pass, expect.results, results, "=") {
return
}
// Everything must match.
if !matchParams(pass, expect.args, args, "") || !matchParams(pass, expect.results, results, "") {
expectFmt := id.Name + "(" + argjoin(expect.args) + ")"
if len(expect.results) == 1 {
expectFmt += " " + argjoin(expect.results)
} else if len(expect.results) > 1 {
expectFmt += " (" + argjoin(expect.results) + ")"
}
actual := typeString(sign)
actual = strings.TrimPrefix(actual, "func")
actual = id.Name + actual
pass.ReportRangef(id, "method %s should have signature %s", actual, expectFmt)
}
}
func typeString(typ types.Type) string {
return types.TypeString(typ, (*types.Package).Name)
}
func argjoin(x []string) string {
y := make([]string, len(x))
for i, s := range x {
if s[0] == '=' {
s = s[1:]
}
y[i] = s
}
return strings.Join(y, ", ")
}
// Does each type in expect with the given prefix match the corresponding type in actual?
func matchParams(pass *analysis.Pass, expect []string, actual *types.Tuple, prefix string) bool {
for i, x := range expect {
if !strings.HasPrefix(x, prefix) {
continue
}
if i >= actual.Len() {
return false
}
if !matchParamType(x, actual.At(i).Type()) {
return false
}
}
if prefix == "" && actual.Len() > len(expect) {
return false
}
return true
}
// Does this one type match?
func matchParamType(expect string, actual types.Type) bool {
expect = strings.TrimPrefix(expect, "=")
// Overkill but easy.
return typeString(actual) == expect
}