Merge e4a5fb1 into a258616

README.md

@@ -29,6 +29,7 @@ $ go vet -vettool=`which gostyle`
 - [**Guide**](https://google.github.io/styleguide/go/guide)
   - [mixedcaps](analyzer/guide/mixedcaps) ... based on https://google.github.io/styleguide/go/guide#mixed-caps
 - [**Decisions**](https://google.github.io/styleguide/go/decisions)
+  - [nilslices](analyzer/decisions/nilslices) ... based on https://google.github.io/styleguide/go/decisions#nil-slices
   - [pkgnames](analyzer/decisions/pkgnames) ... based on https://google.github.io/styleguide/go/decisions#package-names
   - [recvnames](analyzer/decisions/recvnames) ... based on https://google.github.io/styleguide/go/decisions#receiver-names
   - [repetition](analyzer/decisions/repetition) ... based on https://google.github.io/styleguide/go/decisions#repetition
@@ -93,6 +94,14 @@ analyzers-settings:
       - EXPECT
 ```
 
+#### nilslices
+
+```yaml
+analyzers-settings:
+  nilslices:
+    include-generated: false # include generated codes (default: false)
+```
+
 #### pkgnames
 
 ```yaml

analyzer/decisions/nilslices/nilslices.go

@@ -0,0 +1,115 @@
+package nilslices
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+
+	"github.com/gostaticanalysis/comment/passes/commentmap"
+	"github.com/k1LoW/gostyle/config"
+	"github.com/k1LoW/gostyle/reporter"
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+const (
+	name = "nilslices"
+	doc  = "Analyzer based on https://google.github.io/styleguide/go/decisions#nil-slices"
+	msg  = "if you declare an empty slice as a local variable (especially if it can be the source of a return value), prefer the nil initialization to reduce the risk of bugs by callers. (ref: https://google.github.io/styleguide/go/decisions#nil-slices)"
+)
+
+var (
+	disable          bool
+	includeGenerated bool
+)
+
+// Analyzer based on https://google.github.io/styleguide/go/guide#nil-slices
+var Analyzer = &analysis.Analyzer{
+	Name: name,
+	Doc:  doc,
+	Run:  run,
+	Requires: []*analysis.Analyzer{
+		config.Loader,
+		inspect.Analyzer,
+		commentmap.Analyzer,
+	},
+}
+
+func run(pass *analysis.Pass) (any, error) {
+	c, err := config.Load(pass)
+	if err != nil {
+		return nil, err
+	}
+	if c != nil {
+		disable = c.IsDisabled(name)
+		includeGenerated = c.AnalyzersSettings.Nilslices.IncludeGenerated
+	}
+	if disable {
+		return nil, nil
+	}
+	i, ok := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+	if !ok {
+		return nil, fmt.Errorf("unexpected result type from inspect: %T", pass.ResultOf[inspect.Analyzer])
+	}
+
+	nodeFilter := []ast.Node{
+		(*ast.ValueSpec)(nil),
+		(*ast.AssignStmt)(nil),
+	}
+
+	var opts []reporter.Option
+	if includeGenerated {
+		opts = append(opts, reporter.IncludeGenerated())
+	}
+	r, err := reporter.New(name, pass, opts...)
+	if err != nil {
+		return nil, err
+	}
+	i.Preorder(nodeFilter, func(n ast.Node) {
+		switch n := n.(type) {
+		case *ast.ValueSpec:
+			for i, v := range n.Values {
+				c, ok := v.(*ast.CompositeLit)
+				if !ok {
+					continue
+				}
+				if c.Elts != nil {
+					continue
+				}
+				if _, ok := c.Type.(*ast.ArrayType); !ok {
+					continue
+				}
+				r.Append(n.Pos(), fmt.Sprintf("%s: %s", msg, n.Names[i].Name))
+			}
+		case *ast.AssignStmt:
+			if n.Tok != token.DEFINE {
+				return
+			}
+			for i, e := range n.Rhs {
+				c, ok := e.(*ast.CompositeLit)
+				if !ok {
+					continue
+				}
+				if c.Elts != nil {
+					continue
+				}
+				if _, ok := c.Type.(*ast.ArrayType); !ok {
+					continue
+				}
+				id, ok := n.Lhs[i].(*ast.Ident)
+				if !ok {
+					continue
+				}
+				r.Append(n.Pos(), fmt.Sprintf("%s: %s", msg, id.Name))
+			}
+		}
+	})
+	r.Report()
+	return nil, nil
+}
+
+func init() {
+	Analyzer.Flags.BoolVar(&disable, "disable", false, "disable "+name+" analyzer")
+	Analyzer.Flags.BoolVar(&includeGenerated, "include-generated", false, "include generated codes")
+}

analyzer/decisions/nilslices/nilslices_test.go

@@ -0,0 +1,14 @@
+package nilslices
+
+import (
+	"testing"
+
+	"github.com/gostaticanalysis/testutil"
+	"golang.org/x/tools/go/analysis/analysistest"
+)
+
+// TestAnalyzer is a test for Analyzer.
+func TestAnalyzer(t *testing.T) {
+	td := testutil.WithModules(t, analysistest.TestData(), nil)
+	analysistest.Run(t, td, Analyzer, "a")
+}

analyzer/decisions/nilslices/testdata/src/a/a.go

@@ -0,0 +1,16 @@
+package a
+
+var s = []string{} // want "gostyle.nilslices"
+
+var s2 = []string{"a", "b", "c"}
+
+func f() {
+	s := []string{} // want "gostyle.nilslices"
+	print(s)
+	var s2 []string
+	print(s2)
+	s3 := []string{"a", "b", "c"}
+	print(s3)
+	s4 := []string{} //nostyle:nilslices
+	print(s4)
+}

analyzer/decisions/nilslices/testdata/src/a/a_test.go

@@ -0,0 +1,11 @@
+package a_test
+
+import "testing"
+
+func TestA(t *testing.T) {
+	t.Error(1)
+}
+
+func Test_B(t *testing.T) {
+	t.Error(1)
+}

analyzer/decisions/nilslices/testdata/src/a/go.mod

@@ -0,0 +1,4 @@
+module a
+
+go 1.21
+

analyzer/decisions/pkgnames/pkgnames.go

@@ -66,7 +66,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.ImportSpec)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/decisions/recvnames/recvnames.go

@@ -59,7 +59,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.FuncDecl)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/decisions/repetition/repetition.go

@@ -67,7 +67,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.FuncDecl)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/decisions/underscores/underscores.go

@@ -70,7 +70,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.RangeStmt)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/decisions/varnames/varnames.go

@@ -85,7 +85,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.RangeStmt)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/effective/ifacenames/ifacenames.go

@@ -63,7 +63,7 @@ func run(pass *analysis.Pass) (any, error) {
 	}
 
 	var ii *ast.Ident
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

analyzer/guide/mixedcaps/mixedcaps.go

@@ -70,7 +70,7 @@ func run(pass *analysis.Pass) (any, error) {
 		(*ast.RangeStmt)(nil),
 	}
 
-	opts := []reporter.Option{}
+	var opts []reporter.Option
 	if includeGenerated {
 		opts = append(opts, reporter.IncludeGenerated())
 	}

config/config.go

@@ -38,6 +38,7 @@ type Analyzers struct {
 type AnalyzersSettings struct {
 	Ifacenames  Ifacenames  `yaml:"ifacenames"`
 	Mixedcaps   Mixedcaps   `yaml:"mixedcaps"`
+	Nilslices   Nilslices   `yaml:"nilslices"`
 	Pkgnames    Pkgnames    `yaml:"pkgnames"`
 	Recvnames   Recvnames   `yaml:"recvnames"`
 	Repetition  Repetition  `yaml:"repetition"`
@@ -55,6 +56,10 @@ type Mixedcaps struct {
 	IncludeGenerated bool     `yaml:"include-generated"`
 }
 
+type Nilslices struct {
+	IncludeGenerated bool `yaml:"include-generated"`
+}
+
 type Pkgnames struct {
 	IncludeGenerated bool `yaml:"include-generated"`
 }

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"github.com/k1LoW/gostyle/analyzer/decisions/nilslices"
 	"github.com/k1LoW/gostyle/analyzer/decisions/pkgnames"
 	"github.com/k1LoW/gostyle/analyzer/decisions/recvnames"
 	"github.com/k1LoW/gostyle/analyzer/decisions/repetition"
@@ -18,6 +19,7 @@ func main() {
 		ifacenames.Analyzer,
 		pkgnames.Analyzer,
 		mixedcaps.Analyzer,
+		nilslices.Analyzer,
 		recvnames.Analyzer,
 		repetition.Analyzer,
 		underscores.Analyzer,