honnef.co/go/tools@v0.5.0-0.dev.0.20240520180541-dcae280a5e87/stylecheck/st1008/st1008.go (about)

     1  package st1008
     2  
     3  import (
     4  	"go/types"
     5  
     6  	"honnef.co/go/tools/analysis/lint"
     7  	"honnef.co/go/tools/analysis/report"
     8  	"honnef.co/go/tools/internal/passes/buildir"
     9  
    10  	"golang.org/x/tools/go/analysis"
    11  )
    12  
    13  var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
    14  	Analyzer: &analysis.Analyzer{
    15  		Name:     "ST1008",
    16  		Run:      run,
    17  		Requires: []*analysis.Analyzer{buildir.Analyzer},
    18  	},
    19  	Doc: &lint.Documentation{
    20  		Title:   `A function's error value should be its last return value`,
    21  		Text:    `A function's error value should be its last return value.`,
    22  		Since:   `2019.1`,
    23  		MergeIf: lint.MergeIfAny,
    24  	},
    25  })
    26  
    27  var Analyzer = SCAnalyzer.Analyzer
    28  
    29  func run(pass *analysis.Pass) (interface{}, error) {
    30  fnLoop:
    31  	for _, fn := range pass.ResultOf[buildir.Analyzer].(*buildir.IR).SrcFuncs {
    32  		sig := fn.Type().(*types.Signature)
    33  		rets := sig.Results()
    34  		if rets == nil || rets.Len() < 2 {
    35  			continue
    36  		}
    37  
    38  		if types.Unalias(rets.At(rets.Len()-1).Type()) == types.Universe.Lookup("error").Type() {
    39  			// Last return type is error. If the function also returns
    40  			// errors in other positions, that's fine.
    41  			continue
    42  		}
    43  
    44  		if rets.Len() >= 2 &&
    45  			types.Unalias(rets.At(rets.Len()-1).Type()) == types.Universe.Lookup("bool").Type() &&
    46  			types.Unalias(rets.At(rets.Len()-2).Type()) == types.Universe.Lookup("error").Type() {
    47  			// Accept (..., error, bool) and assume it's a comma-ok function. It's not clear whether the bool should come last or not for these kinds of functions.
    48  			continue
    49  		}
    50  		for i := rets.Len() - 2; i >= 0; i-- {
    51  			if types.Unalias(rets.At(i).Type()) == types.Universe.Lookup("error").Type() {
    52  				report.Report(pass, rets.At(i), "error should be returned as the last argument", report.ShortRange())
    53  				continue fnLoop
    54  			}
    55  		}
    56  	}
    57  	return nil, nil
    58  }