sa4014.go raw

   1  package sa4014
   2  
   3  import (
   4  	"go/ast"
   5  
   6  	"honnef.co/go/tools/analysis/code"
   7  	"honnef.co/go/tools/analysis/lint"
   8  	"honnef.co/go/tools/analysis/report"
   9  
  10  	"golang.org/x/tools/go/analysis"
  11  	"golang.org/x/tools/go/analysis/passes/inspect"
  12  )
  13  
  14  var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
  15  	Analyzer: &analysis.Analyzer{
  16  		Name:     "SA4014",
  17  		Run:      run,
  18  		Requires: []*analysis.Analyzer{inspect.Analyzer},
  19  	},
  20  	Doc: &lint.RawDocumentation{
  21  		Title:    `An if/else if chain has repeated conditions and no side-effects; if the condition didn't match the first time, it won't match the second time, either`,
  22  		Since:    "2017.1",
  23  		Severity: lint.SeverityWarning,
  24  		MergeIf:  lint.MergeIfAll,
  25  	},
  26  })
  27  
  28  var Analyzer = SCAnalyzer.Analyzer
  29  
  30  func run(pass *analysis.Pass) (interface{}, error) {
  31  	seen := map[ast.Node]bool{}
  32  
  33  	var collectConds func(ifstmt *ast.IfStmt, conds []ast.Expr) ([]ast.Expr, bool)
  34  	collectConds = func(ifstmt *ast.IfStmt, conds []ast.Expr) ([]ast.Expr, bool) {
  35  		seen[ifstmt] = true
  36  		// Bail if any if-statement has an Init statement or side effects in its condition
  37  		if ifstmt.Init != nil {
  38  			return nil, false
  39  		}
  40  		if code.MayHaveSideEffects(pass, ifstmt.Cond, nil) {
  41  			return nil, false
  42  		}
  43  
  44  		conds = append(conds, ifstmt.Cond)
  45  		if elsestmt, ok := ifstmt.Else.(*ast.IfStmt); ok {
  46  			return collectConds(elsestmt, conds)
  47  		}
  48  		return conds, true
  49  	}
  50  	fn := func(node ast.Node) {
  51  		ifstmt := node.(*ast.IfStmt)
  52  		if seen[ifstmt] {
  53  			// this if-statement is part of an if/else-if chain that we've already processed
  54  			return
  55  		}
  56  		if ifstmt.Else == nil {
  57  			// there can be at most one condition
  58  			return
  59  		}
  60  		conds, ok := collectConds(ifstmt, nil)
  61  		if !ok {
  62  			return
  63  		}
  64  		if len(conds) < 2 {
  65  			return
  66  		}
  67  		counts := map[string]int{}
  68  		for _, cond := range conds {
  69  			s := report.Render(pass, cond)
  70  			counts[s]++
  71  			if counts[s] == 2 {
  72  				report.Report(pass, cond, "this condition occurs multiple times in this if/else if chain")
  73  			}
  74  		}
  75  	}
  76  	code.Preorder(pass, fn, (*ast.IfStmt)(nil))
  77  	return nil, nil
  78  }
  79