Function addCode

rewrite.go:47–97

addCode searches for main func in data, and updates AST code adding tracing functions.

(path string)

// addCode searches for main func in data, and updates AST code
// adding tracing functions.
func addCode(path string) ([]byte, error) {
	var conf loader.Config
	if _, err := conf.FromArgs([]string{path}, false); err != nil {
		return nil, err
	}

	prog, err := conf.Load()
	if err != nil {
		return nil, err
	}

	// check if runtime/trace already imported
	for i, _ := range prog.Imported {
		if i == "runtime/trace" {
			return nil, ErrImported
		}
	}

	pkg := prog.Created[0]

	// TODO: find file with main func inside
	astFile := pkg.Files[0]

	// add imports
	astutil.AddImport(prog.Fset, astFile, "os")
	astutil.AddImport(prog.Fset, astFile, "runtime/trace")
	astutil.AddImport(prog.Fset, astFile, "time")

	// add start/stop code
	ast.Inspect(astFile, func(n ast.Node) bool {
		switch x := n.(type) {
		case *ast.FuncDecl:
			// find 'main' function
			if x.Name.Name == "main" && x.Recv == nil {
				stmts := createTraceStmts()
				stmts = append(stmts, x.Body.List...)
				x.Body.List = stmts
				return true
			}
		}
		return true
	})

	var buf bytes.Buffer
	err = printer.Fprint(&buf, prog.Fset, astFile)
	if err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}

func createTraceStmts() []ast.Stmt {
	ret := make([]ast.Stmt, 2)