vet_diags.go

package main

import (
	"fmt"
	"go/ast"
	"go/token"
	"go/types"
	"strings"

	"golang.org/x/tools/go/analysis"
	"golang.org/x/tools/go/analysis/passes/inspect"
	"golang.org/x/tools/go/analysis/unitchecker"
	"golang.org/x/tools/go/ast/inspector"
)

var Analyzer = &analysis.Analyzer{
	Name:     "diags",
	Doc:      "check for diagnostic assignments to error variables",
	Requires: []*analysis.Analyzer{inspect.Analyzer},
	Run:      run,
}

func run(pass *analysis.Pass) (interface{}, error) {
	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)

	nodeFilter := []ast.Node{
		(*ast.AssignStmt)(nil),
	}
	inspect.Preorder(nodeFilter, func(n ast.Node) {
		stmt := n.(*ast.AssignStmt)
		if stmt.Tok != token.DEFINE {
			return // ignore =
		}

		for _, x := range stmt.Lhs {
			id, isId := x.(*ast.Ident)
			if !isId {
				continue
			}

			// any e, err, myErr, etc
			if !(id.Name == "e" || strings.Contains(id.Name, "err") || strings.Contains(id.Name, "Err")) {
				continue
			}

			def := pass.TypesInfo.Defs[id]
			if def == nil {
				continue
			}
			named, ok := def.Type().(*types.Named)
			if !ok {
				continue
			}
			typeName := named.Obj().Name()

			if strings.HasPrefix(typeName, "Diagnostic") {
				pass.Reportf(stmt.Pos(), fmt.Sprintf("%s type assigned to variable named %q", typeName, id.Name))
			}
		}
	})

	return nil, nil
}

func main() {
	unitchecker.Main(Analyzer)
}