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package rule
import (
"fmt"
"go/ast"
"go/token"
"github.com/mgechev/revive/lint"
)
// SuperfluousElseRule lints given else constructs.
type SuperfluousElseRule struct{}
// Apply applies the rule to given file.
func (r *SuperfluousElseRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
var failures []lint.Failure
onFailure := func(failure lint.Failure) {
failures = append(failures, failure)
}
var branchingFunctions = map[string]map[string]bool{
"os": map[string]bool{"Exit": true},
"log": map[string]bool{
"Fatal": true,
"Fatalf": true,
"Fatalln": true,
"Panic": true,
"Panicf": true,
"Panicln": true,
},
}
w := lintSuperfluousElse{make(map[*ast.IfStmt]bool), onFailure, branchingFunctions}
ast.Walk(w, file.AST)
return failures
}
// Name returns the rule name.
func (r *SuperfluousElseRule) Name() string {
return "superfluous-else"
}
type lintSuperfluousElse struct {
ignore map[*ast.IfStmt]bool
onFailure func(lint.Failure)
branchingFunctions map[string]map[string]bool
}
func (w lintSuperfluousElse) Visit(node ast.Node) ast.Visitor {
ifStmt, ok := node.(*ast.IfStmt)
if !ok || ifStmt.Else == nil {
return w
}
if w.ignore[ifStmt] {
if elseif, ok := ifStmt.Else.(*ast.IfStmt); ok {
w.ignore[elseif] = true
}
return w
}
if elseif, ok := ifStmt.Else.(*ast.IfStmt); ok {
w.ignore[elseif] = true
return w
}
if _, ok := ifStmt.Else.(*ast.BlockStmt); !ok {
// only care about elses without conditions
return w
}
if len(ifStmt.Body.List) == 0 {
return w
}
shortDecl := false // does the if statement have a ":=" initialization statement?
if ifStmt.Init != nil {
if as, ok := ifStmt.Init.(*ast.AssignStmt); ok && as.Tok == token.DEFINE {
shortDecl = true
}
}
extra := ""
if shortDecl {
extra = " (move short variable declaration to its own line if necessary)"
}
lastStmt := ifStmt.Body.List[len(ifStmt.Body.List)-1]
switch stmt := lastStmt.(type) {
case *ast.BranchStmt:
token := stmt.Tok.String()
if token != "fallthrough" {
w.onFailure(newFailure(ifStmt.Else, "if block ends with a "+token+" statement, so drop this else and outdent its block"+extra))
}
case *ast.ExprStmt:
if ce, ok := stmt.X.(*ast.CallExpr); ok { // it's a function call
if fc, ok := ce.Fun.(*ast.SelectorExpr); ok {
if id, ok := fc.X.(*ast.Ident); ok {
fn := fc.Sel.Name
pkg := id.Name
if w.branchingFunctions[pkg][fn] { // it's a call to a branching function
w.onFailure(
newFailure(ifStmt.Else, fmt.Sprintf("if block ends with call to %s.%s function, so drop this else and outdent its block%s", pkg, fn, extra)))
}
}
}
}
}
return w
}
func newFailure(node ast.Node, msg string) lint.Failure {
return lint.Failure{
Confidence: 1,
Node: node,
Category: "indent",
Failure: msg,
}
}
|
