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|
package rule
import (
"fmt"
"go/ast"
"github.com/mgechev/revive/lint"
)
// UnusedParamRule lints unused params in functions.
type UnusedParamRule struct{}
// Apply applies the rule to given file.
func (r *UnusedParamRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
var failures []lint.Failure
onFailure := func(failure lint.Failure) {
failures = append(failures, failure)
}
w := lintUnusedParamRule{onFailure: onFailure}
ast.Walk(w, file.AST)
return failures
}
// Name returns the rule name.
func (r *UnusedParamRule) Name() string {
return "unused-parameter"
}
type lintUnusedParamRule struct {
onFailure func(lint.Failure)
}
func (w lintUnusedParamRule) Visit(node ast.Node) ast.Visitor {
switch n := node.(type) {
case *ast.FuncDecl:
params := retrieveNamedParams(n.Type.Params)
if len(params) < 1 {
return nil // skip, func without parameters
}
if n.Body == nil {
return nil // skip, is a function prototype
}
// inspect the func body looking for references to parameters
fselect := func(n ast.Node) bool {
ident, isAnID := n.(*ast.Ident)
if !isAnID {
return false
}
_, isAParam := params[ident.Obj]
if isAParam {
params[ident.Obj] = false // mark as used
}
return false
}
_ = pick(n.Body, fselect, nil)
for _, p := range n.Type.Params.List {
for _, n := range p.Names {
if params[n.Obj] {
w.onFailure(lint.Failure{
Confidence: 1,
Node: n,
Category: "bad practice",
Failure: fmt.Sprintf("parameter '%s' seems to be unused, consider removing or renaming it as _", n.Name),
})
}
}
}
return nil // full method body already inspected
}
return w
}
func retrieveNamedParams(params *ast.FieldList) map[*ast.Object]bool {
result := map[*ast.Object]bool{}
if params.List == nil {
return result
}
for _, p := range params.List {
for _, n := range p.Names {
if n.Name == "_" {
continue
}
result[n.Obj] = true
}
}
return result
}
|
