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// 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 sigchanyzer defines an Analyzer that detects
// misuse of unbuffered signal as argument to signal.Notify.
package sigchanyzer
import (
"bytes"
"go/ast"
"go/format"
"go/token"
"go/types"
"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 unbuffered channel of os.Signal
This checker reports call expression of the form signal.Notify(c <-chan os.Signal, sig ...os.Signal),
where c is an unbuffered channel, which can be at risk of missing the signal.`
// Analyzer describes sigchanyzer analysis function detector.
var Analyzer = &analysis.Analyzer{
Name: "sigchanyzer",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.CallExpr)(nil),
}
inspect.Preorder(nodeFilter, func(n ast.Node) {
call := n.(*ast.CallExpr)
if !isSignalNotify(pass.TypesInfo, call) {
return
}
var chanDecl *ast.CallExpr
switch arg := call.Args[0].(type) {
case *ast.Ident:
if decl, ok := findDecl(arg).(*ast.CallExpr); ok {
chanDecl = decl
}
case *ast.CallExpr:
// Only signal.Notify(make(chan os.Signal), os.Interrupt) is safe,
// conservatively treate others as not safe, see golang/go#45043
if isBuiltinMake(pass.TypesInfo, arg) {
return
}
chanDecl = arg
}
if chanDecl == nil || len(chanDecl.Args) != 1 {
return
}
// Make a copy of the channel's declaration to avoid
// mutating the AST. See https://golang.org/issue/46129.
chanDeclCopy := &ast.CallExpr{}
*chanDeclCopy = *chanDecl
chanDeclCopy.Args = append([]ast.Expr(nil), chanDecl.Args...)
chanDeclCopy.Args = append(chanDeclCopy.Args, &ast.BasicLit{
Kind: token.INT,
Value: "1",
})
var buf bytes.Buffer
if err := format.Node(&buf, token.NewFileSet(), chanDeclCopy); err != nil {
return
}
pass.Report(analysis.Diagnostic{
Pos: call.Pos(),
End: call.End(),
Message: "misuse of unbuffered os.Signal channel as argument to signal.Notify",
SuggestedFixes: []analysis.SuggestedFix{{
Message: "Change to buffer channel",
TextEdits: []analysis.TextEdit{{
Pos: chanDecl.Pos(),
End: chanDecl.End(),
NewText: buf.Bytes(),
}},
}},
})
})
return nil, nil
}
func isSignalNotify(info *types.Info, call *ast.CallExpr) bool {
check := func(id *ast.Ident) bool {
obj := info.ObjectOf(id)
return obj.Name() == "Notify" && obj.Pkg().Path() == "os/signal"
}
switch fun := call.Fun.(type) {
case *ast.SelectorExpr:
return check(fun.Sel)
case *ast.Ident:
if fun, ok := findDecl(fun).(*ast.SelectorExpr); ok {
return check(fun.Sel)
}
return false
default:
return false
}
}
func findDecl(arg *ast.Ident) ast.Node {
if arg.Obj == nil {
return nil
}
switch as := arg.Obj.Decl.(type) {
case *ast.AssignStmt:
if len(as.Lhs) != len(as.Rhs) {
return nil
}
for i, lhs := range as.Lhs {
lid, ok := lhs.(*ast.Ident)
if !ok {
continue
}
if lid.Obj == arg.Obj {
return as.Rhs[i]
}
}
case *ast.ValueSpec:
if len(as.Names) != len(as.Values) {
return nil
}
for i, name := range as.Names {
if name.Obj == arg.Obj {
return as.Values[i]
}
}
}
return nil
}
func isBuiltinMake(info *types.Info, call *ast.CallExpr) bool {
typVal := info.Types[call.Fun]
if !typVal.IsBuiltin() {
return false
}
switch fun := call.Fun.(type) {
case *ast.Ident:
return info.ObjectOf(fun).Name() == "make"
default:
return false
}
}
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