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
|
// Copyright 2020 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 unusedparams defines an analyzer that checks for unused
// parameters of functions.
package unusedparams
import (
"fmt"
"go/ast"
"go/types"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
)
const Doc = `check for unused parameters of functions
The unusedparams analyzer checks functions to see if there are
any parameters that are not being used.
To reduce false positives it ignores:
- methods
- parameters that do not have a name or are underscored
- functions in test files
- functions with empty bodies or those with just a return stmt`
var Analyzer = &analysis.Analyzer{
Name: "unusedparams",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
}
type paramData struct {
field *ast.Field
ident *ast.Ident
typObj types.Object
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.FuncDecl)(nil),
(*ast.FuncLit)(nil),
}
inspect.Preorder(nodeFilter, func(n ast.Node) {
var fieldList *ast.FieldList
var body *ast.BlockStmt
// Get the fieldList and body from the function node.
switch f := n.(type) {
case *ast.FuncDecl:
fieldList, body = f.Type.Params, f.Body
// TODO(golang/go#36602): add better handling for methods, if we enable methods
// we will get false positives if a struct is potentially implementing
// an interface.
if f.Recv != nil {
return
}
// Ignore functions in _test.go files to reduce false positives.
if file := pass.Fset.File(n.Pos()); file != nil && strings.HasSuffix(file.Name(), "_test.go") {
return
}
case *ast.FuncLit:
fieldList, body = f.Type.Params, f.Body
}
// If there are no arguments or the function is empty, then return.
if fieldList.NumFields() == 0 || body == nil || len(body.List) == 0 {
return
}
switch expr := body.List[0].(type) {
case *ast.ReturnStmt:
// Ignore functions that only contain a return statement to reduce false positives.
return
case *ast.ExprStmt:
callExpr, ok := expr.X.(*ast.CallExpr)
if !ok || len(body.List) > 1 {
break
}
// Ignore functions that only contain a panic statement to reduce false positives.
if fun, ok := callExpr.Fun.(*ast.Ident); ok && fun.Name == "panic" {
return
}
}
// Get the useful data from each field.
params := make(map[string]*paramData)
unused := make(map[*paramData]bool)
for _, f := range fieldList.List {
for _, i := range f.Names {
if i.Name == "_" {
continue
}
params[i.Name] = ¶mData{
field: f,
ident: i,
typObj: pass.TypesInfo.ObjectOf(i),
}
unused[params[i.Name]] = true
}
}
// Traverse through the body of the function and
// check to see which parameters are unused.
ast.Inspect(body, func(node ast.Node) bool {
n, ok := node.(*ast.Ident)
if !ok {
return true
}
param, ok := params[n.Name]
if !ok {
return false
}
if nObj := pass.TypesInfo.ObjectOf(n); nObj != param.typObj {
return false
}
delete(unused, param)
return false
})
// Create the reports for the unused parameters.
for u := range unused {
start, end := u.field.Pos(), u.field.End()
if len(u.field.Names) > 1 {
start, end = u.ident.Pos(), u.ident.End()
}
// TODO(golang/go#36602): Add suggested fixes to automatically
// remove the unused parameter from every use of this
// function.
pass.Report(analysis.Diagnostic{
Pos: start,
End: end,
Message: fmt.Sprintf("potentially unused parameter: '%s'", u.ident.Name),
SuggestedFixes: []analysis.SuggestedFix{{
Message: `Replace with "_"`,
TextEdits: []analysis.TextEdit{{
Pos: u.ident.Pos(),
End: u.ident.End(),
NewText: []byte("_"),
}},
}},
})
}
})
return nil, nil
}
|
