cmd/vet: bring in sigchanyzer to report unbuffered channels to signal.Notify

Brings in the static analyzer "sigchanyzer", that we created at
Orijtech, Inc, and already submitted in CL 274352, as

    golang.org/x/tools/go/analysis/passes/sigchanyzer

and add it to cmd/vet as one of the passes.

Fixes #9399

Change-Id: I83708b8ea5ca8ede5ee31efab55cbce7419434ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/299532
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Bryan C. Mills <bcmills@google.com>

src/cmd/vendor/golang.org/x/tools/go/analysis/passes/sigchanyzer/sigchanyzer.go

@@ -0,0 +1,129 @@
+// 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:
+			chanDecl = arg
+		}
+		if chanDecl == nil || len(chanDecl.Args) != 1 {
+			return
+		}
+		chanDecl.Args = append(chanDecl.Args, &ast.BasicLit{
+			Kind:  token.INT,
+			Value: "1",
+		})
+		var buf bytes.Buffer
+		if err := format.Node(&buf, token.NewFileSet(), chanDecl); 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
+}

src/cmd/vendor/modules.txt

@@ -69,6 +69,7 @@ golang.org/x/tools/go/analysis/passes/lostcancel
 golang.org/x/tools/go/analysis/passes/nilfunc
 golang.org/x/tools/go/analysis/passes/printf
 golang.org/x/tools/go/analysis/passes/shift
+golang.org/x/tools/go/analysis/passes/sigchanyzer
 golang.org/x/tools/go/analysis/passes/stdmethods
 golang.org/x/tools/go/analysis/passes/stringintconv
 golang.org/x/tools/go/analysis/passes/structtag

src/cmd/vet/main.go

@@ -22,6 +22,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/nilfunc"
 	"golang.org/x/tools/go/analysis/passes/printf"
 	"golang.org/x/tools/go/analysis/passes/shift"
+	"golang.org/x/tools/go/analysis/passes/sigchanyzer"
 	"golang.org/x/tools/go/analysis/passes/stdmethods"
 	"golang.org/x/tools/go/analysis/passes/stringintconv"
 	"golang.org/x/tools/go/analysis/passes/structtag"
@@ -54,6 +55,7 @@ func main() {
 		nilfunc.Analyzer,
 		printf.Analyzer,
 		shift.Analyzer,
+		sigchanyzer.Analyzer,
 		stdmethods.Analyzer,
 		stringintconv.Analyzer,
 		structtag.Analyzer,