go/analysis/passes/initflagparse: add check for avoid flag.Parse at init

go/analysis/passes/initflagparse/initflagparse.go

@@ -0,0 +1,79 @@
+// Copyright 2014 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 initflagparse defines an Analyzer that checks for invalid
+// usages of flag.Parse during package initialization
+package initflagparse
+
+import (
+	"go/ast"
+	"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 calls to flag.Parse within packages init
+
+The initflagparse analyzer reports incorrect calls to flag.Parse within
+the init of the packages.`
+
+var Analyzer = &analysis.Analyzer{
+	Name:     "initflagparse",
+	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.FuncDecl)(nil),
+	}
+	inspect.Preorder(nodeFilter, func(n ast.Node) {
+		x := n.(*ast.FuncDecl)
+		if x.Recv == nil && x.Name.Name == "init" {
+			checkForFlagParse(pass, x)
+		}
+	})
+	return nil, nil
+}
+
+// checkForFlagParse check the code inside a node and fail if it finds a
+// flag.Parse call
+func checkForFlagParse(pass *analysis.Pass, x ast.Node) {
+	ast.Inspect(x, func(n ast.Node) bool {
+		x, ok := n.(*ast.CallExpr)
+		if !ok {
+			return true
+		}
+		fun, ok := x.Fun.(*ast.SelectorExpr)
+		if !ok {
+			return true
+		}
+
+		module, ok := fun.X.(*ast.Ident)
+		if !ok {
+			return true
+		}
+
+		obj := pass.TypesInfo.ObjectOf(module)
+		if obj == nil {
+			return true
+		}
+
+		pkgObj, ok := obj.(*types.PkgName)
+		if !ok || pkgObj.Imported() == nil {
+			return true
+		}
+
+		if ok && obj != nil && pkgObj.Imported().Name() == "flag" && fun.Sel.Name == "Parse" {
+			pass.ReportRangef(x, "flag.Parse call within package initialization")
+			return false
+		}
+		return true
+	})
+}

go/analysis/passes/initflagparse/initflagparse_test.go

@@ -0,0 +1,18 @@
+// Copyright 2018 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 initflagparse_test
+
+import (
+	"testing"
+
+	"golang.org/x/tools/go/analysis/analysistest"
+	"golang.org/x/tools/go/analysis/passes/initflagparse"
+)
+
+func Test(t *testing.T) {
+	testdata := analysistest.TestData()
+	analysistest.Run(t, testdata, initflagparse.Analyzer, "a")
+	analysistest.Run(t, testdata, initflagparse.Analyzer, "b")
+}

go/analysis/passes/initflagparse/testdata/src/a/a.go

@@ -0,0 +1,21 @@
+// Copyright 2014 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 a
+
+import "flag"
+
+func init() {
+	flag.Parse() // want `flag.Parse call within package initialization`
+}
+
+type Test struct{}
+
+func (_ *Test) init() {
+	flag.Parse()
+}
+
+func main() {
+	flag.Parse()
+}

go/analysis/passes/initflagparse/testdata/src/b/b.go

@@ -0,0 +1,21 @@
+// Copyright 2014 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 b
+
+import x "flag"
+
+func init() {
+	x.Parse() // want `flag.Parse call within package initialization`
+}
+
+type Test struct{}
+
+func (_ *Test) init() {
+	x.Parse()
+}
+
+func main() {
+	x.Parse()
+}

go/analysis/unitchecker/main.go

@@ -24,6 +24,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/copylock"
 	"golang.org/x/tools/go/analysis/passes/errorsas"
 	"golang.org/x/tools/go/analysis/passes/httpresponse"
+	"golang.org/x/tools/go/analysis/passes/initflagparse"
 	"golang.org/x/tools/go/analysis/passes/loopclosure"
 	"golang.org/x/tools/go/analysis/passes/lostcancel"
 	"golang.org/x/tools/go/analysis/passes/nilfunc"
@@ -62,5 +63,6 @@ func main() {
 		unreachable.Analyzer,
 		unsafeptr.Analyzer,
 		unusedresult.Analyzer,
+		initflagparse.Analyzer,
 	)
 }