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