revive/rule/empty-block.go

package rule

import (
	"go/ast"
	"go/types"

	"github.com/mgechev/revive/lint"
)

// EmptyBlockRule lints given else constructs.
type EmptyBlockRule struct{}

// Apply applies the rule to given file.
func (r *EmptyBlockRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
	var failures []lint.Failure

	onFailure := func(failure lint.Failure) {
		failures = append(failures, failure)
	}

	err := file.Pkg.TypeCheck()
	if err != nil {
		panic("unable to type check " + file.Name + ":" + err.Error())
	}

	w := lintEmptyBlock{make(map[*ast.BlockStmt]bool, 0), file.Pkg, onFailure}
	ast.Walk(w, file.AST)
	return failures
}

// Name returns the rule name.
func (r *EmptyBlockRule) Name() string {
	return "empty-block"
}

type lintEmptyBlock struct {
	ignore    map[*ast.BlockStmt]bool
	pkg       *lint.Package
	onFailure func(lint.Failure)
}

func (w lintEmptyBlock) Visit(node ast.Node) ast.Visitor {
	switch n := node.(type) {
	case *ast.FuncDecl:
		w.ignore[n.Body] = true
		return w
	case *ast.FuncLit:
		w.ignore[n.Body] = true
		return w
	case *ast.RangeStmt:
		t := w.pkg.TypeOf(n.X)

		if _, ok := t.(*types.Chan); ok {
			w.ignore[n.Body] = true
		}
	case *ast.BlockStmt:
		if !w.ignore[n] && len(n.List) == 0 {
			w.onFailure(lint.Failure{
				Confidence: 1,
				Node:       n,
				Category:   "logic",
				Failure:    "this block is empty, you can remove it",
			})
		}
	}

	return w
}