Golang Application Specific Static Analysis - Checks if a funtion calls mismatched error functions

checker.go

package main

import (
	"flag"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"log"
)

type CallChecker struct {
	Name  string
	Calls []string
}

func (cc *CallChecker) CheckErrorFuncs() {
	if len(cc.Calls) == 0 {
		return
	}

	errorFuncs := map[string]int{}
	for _, fn := range cc.Calls {
		if fn == "jsonError" || fn == "errorPage" {
			errorFuncs[fn] += 1
		}
	}

	if len(errorFuncs) > 1 {
		log.Println(
			cc.Name, errorFuncs["jsonError"], errorFuncs["errorPage"])
	}
}

func (cc *CallChecker) Report() {
	if len(cc.Calls) == 0 {
		return
	}

	log.Printf("%s:\n", cc.Name)
	for _, fn := range cc.Calls {
		log.Printf("\t%s\n", fn)
	}
}

func (cc *CallChecker) Visit(node ast.Node) (w ast.Visitor) {
	// if node != nil {
	// 	log.Printf("%T: %s", node, node)
	// }

	switch node.(type) {
	case *ast.CallExpr:
		e := node.(*ast.CallExpr)
		switch e.Fun.(type) {
		case *ast.Ident:
			id := e.Fun.(*ast.Ident)
			cc.Calls = append(cc.Calls, id.String())
		case *ast.SelectorExpr:
			se := e.Fun.(*ast.SelectorExpr)
			prefix := ""
			switch se.X.(type) {
			case *ast.Ident:
				prefix = se.X.(*ast.Ident).String()
			}

			cc.Calls = append(
				cc.Calls, fmt.Sprintf("%s.%s", prefix, se.Sel.String()))
		}
	}
	return cc
}

func checkFunc(f *ast.FuncDecl) {
	cc := &CallChecker{
		Name:  f.Name.String(),
		Calls: []string{},
	}
	ast.Walk(cc, f)
	// cc.Report()
	cc.CheckErrorFuncs()
}

func main() {
	var fname = flag.String("f", "", "file to parse")
	flag.Parse()

	if len(*fname) == 0 {
		log.Fatal("-f required")
	}

	fset := token.NewFileSet()

	f, err := parser.ParseFile(fset, *fname, nil, 0)
	if err != nil {
		log.Println(err)
		return
	}

	for _, d := range f.Decls {
		switch d.(type) {
		case *ast.FuncDecl:
			f := d.(*ast.FuncDecl)
			checkFunc(f)
		}
	}
}