src

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git clone git://code.dwrz.net/src
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s1036.go (2154B)

      1 package s1036
      2 
      3 import (
      4 	"go/ast"
      5 
      6 	"honnef.co/go/tools/analysis/code"
      7 	"honnef.co/go/tools/analysis/edit"
      8 	"honnef.co/go/tools/analysis/lint"
      9 	"honnef.co/go/tools/analysis/report"
     10 	"honnef.co/go/tools/pattern"
     11 
     12 	"golang.org/x/tools/go/analysis"
     13 )
     14 
     15 var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
     16 	Analyzer: &analysis.Analyzer{
     17 		Name:     "S1036",
     18 		Run:      run,
     19 		Requires: code.RequiredAnalyzers,
     20 	},
     21 	Doc: &lint.RawDocumentation{
     22 		Title: `Unnecessary guard around map access`,
     23 
     24 		Text: `
     25 When accessing a map key that doesn't exist yet, one receives a zero
     26 value. Often, the zero value is a suitable value, for example when
     27 using append or doing integer math.
     28 
     29 The following
     30 
     31     if _, ok := m["foo"]; ok {
     32         m["foo"] = append(m["foo"], "bar")
     33     } else {
     34         m["foo"] = []string{"bar"}
     35     }
     36 
     37 can be simplified to
     38 
     39     m["foo"] = append(m["foo"], "bar")
     40 
     41 and
     42 
     43     if _, ok := m2["k"]; ok {
     44         m2["k"] += 4
     45     } else {
     46         m2["k"] = 4
     47     }
     48 
     49 can be simplified to
     50 
     51     m["k"] += 4
     52 `,
     53 		Since:   "2020.1",
     54 		MergeIf: lint.MergeIfAny,
     55 	},
     56 })
     57 
     58 var Analyzer = SCAnalyzer.Analyzer
     59 
     60 var checkUnnecessaryGuardQ = pattern.MustParse(`
     61 	(Or
     62 		(IfStmt
     63 			(AssignStmt [(Ident "_") ok@(Ident _)] ":=" indexexpr@(IndexExpr _ _))
     64 			ok
     65 			set@(AssignStmt indexexpr "=" (CallExpr (Builtin "append") indexexpr:values))
     66 			(AssignStmt indexexpr "=" (CompositeLit _ values)))
     67 		(IfStmt
     68 			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
     69 			ok
     70 			set@(AssignStmt indexexpr "+=" value)
     71 			(AssignStmt indexexpr "=" value))
     72 		(IfStmt
     73 			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
     74 			ok
     75 			set@(IncDecStmt indexexpr "++")
     76 			(AssignStmt indexexpr "=" (IntegerLiteral "1"))))`)
     77 
     78 func run(pass *analysis.Pass) (any, error) {
     79 	for node, m := range code.Matches(pass, checkUnnecessaryGuardQ) {
     80 		if code.MayHaveSideEffects(pass, m.State["indexexpr"].(ast.Expr), nil) {
     81 			continue
     82 		}
     83 		report.Report(pass, node, "unnecessary guard around map access",
     84 			report.ShortRange(),
     85 			report.Fixes(edit.Fix("Simplify map access", edit.ReplaceWithNode(pass.Fset, node, m.State["set"].(ast.Node)))))
     86 	}
     87 	return nil, nil
     88 }