cmd: add a new analyzer for check missing values after append

If there is no second parameter added during append, there will be no prompt when executing go vet. Add an analyzer to detect this situation

Update #60448

Change-Id: If9848835424f310c54e3e9377aaaad4a1516871a
Reviewed-on: https://go-review.googlesource.com/c/go/+/498416
Run-TryBot: shuang cui <imcusg@gmail.com>
Run-TryBot: Tim King <taking@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

src/cmd/go/internal/test/flagdefs.go

@@ -40,6 +40,7 @@ var passFlagToTest = map[string]bool{
 }
 
 var passAnalyzersToVet = map[string]bool{
+	"appends":          true,
 	"asmdecl":          true,
 	"assign":           true,
 	"atomic":           true,

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

@@ -0,0 +1,49 @@
+// Copyright 2023 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 appends defines an Analyzer that detects
+// if there is only one variable in append.
+package appends
+
+import (
+	_ "embed"
+	"go/ast"
+	"go/types"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+//go:embed doc.go
+var doc string
+
+var Analyzer = &analysis.Analyzer{
+	Name:     "appends",
+	Doc:      analysisutil.MustExtractDoc(doc, "appends"),
+	URL:      "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/appends",
+	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 ident, ok := call.Fun.(*ast.Ident); ok && ident.Name == "append" {
+			if _, ok := pass.TypesInfo.Uses[ident].(*types.Builtin); ok {
+				if len(call.Args) == 1 {
+					pass.ReportRangef(call, "append with no values")
+				}
+			}
+		}
+	})
+
+	return nil, nil
+}

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

@@ -0,0 +1,20 @@
+// Copyright 2023 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 appends defines an Analyzer that detects
+// if there is only one variable in append.
+//
+// # Analyzer appends
+//
+// appends: check for missing values after append
+//
+// This checker reports calls to append that pass
+// no values to be appended to the slice.
+//
+//	s := []string{"a", "b", "c"}
+//	_ = append(s)
+//
+// Such calls are always no-ops and often indicate an
+// underlying mistake.
+package appends

src/cmd/vendor/modules.txt

@@ -52,6 +52,7 @@ golang.org/x/tools/cmd/bisect
 golang.org/x/tools/cover
 golang.org/x/tools/go/analysis
 golang.org/x/tools/go/analysis/internal/analysisflags
+golang.org/x/tools/go/analysis/passes/appends
 golang.org/x/tools/go/analysis/passes/asmdecl
 golang.org/x/tools/go/analysis/passes/assign
 golang.org/x/tools/go/analysis/passes/atomic

src/cmd/vet/main.go

@@ -9,6 +9,7 @@ import (
 
 	"golang.org/x/tools/go/analysis/unitchecker"
 
+	"golang.org/x/tools/go/analysis/passes/appends"
 	"golang.org/x/tools/go/analysis/passes/asmdecl"
 	"golang.org/x/tools/go/analysis/passes/assign"
 	"golang.org/x/tools/go/analysis/passes/atomic"
@@ -46,6 +47,7 @@ func main() {
 	objabi.AddVersionFlag()
 
 	unitchecker.Main(
+		appends.Analyzer,
 		asmdecl.Analyzer,
 		assign.Analyzer,
 		atomic.Analyzer,

src/cmd/vet/testdata/appends/appends.go

@@ -0,0 +1,12 @@
+// Copyright 2023 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.
+
+// This file contains tests for the appends checker.
+
+package appends
+
+func AppendsTest() {
+	sli := []string{"a", "b", "c"}
+	sli = append(sli) // ERROR "append with no values"
+}

src/cmd/vet/vet_test.go

@@ -62,6 +62,7 @@ func vetCmd(t *testing.T, arg, pkg string) *exec.Cmd {
 func TestVet(t *testing.T) {
 	t.Parallel()
 	for _, pkg := range []string{
+		"appends",
 		"asm",
 		"assign",
 		"atomic",