Visitor generator cleanup

Makefile

@@ -89,9 +89,7 @@ parser:
 	make -C go/vt/sqlparser
 
 visitor:
-	go build -o visitorgen go/visitorgen/main/main.go
-	./visitorgen -input=go/vt/sqlparser/ast.go -output=$(REWRITER)
-	rm ./visitorgen
+	go generate go/vt/sqlparser/rewriter.go
 
 # To pass extra flags, run test.go manually.
 # For example: go run test.go -docker=false -- --extra-flag

go/visitorgen/main/main.go → go/vt/sqlparser/visitorgen/main/main.go

@@ -17,44 +17,46 @@ limitations under the License.
 package main
 
 import (
+	"bytes"
 	"flag"
 	"fmt"
 	"go/parser"
 	"go/token"
+	"io/ioutil"
 	"os"
 
-	"vitess.io/vitess/go/visitorgen"
+	"vitess.io/vitess/go/exit"
+	"vitess.io/vitess/go/vt/log"
+
+	"vitess.io/vitess/go/vt/sqlparser/visitorgen"
 )
 
 var (
 	inputFile  = flag.String("input", "", "input file to use")
 	outputFile = flag.String("output", "", "output file")
+	compare    = flag.Bool("compareOnly", false, "instead of writing to the output file, compare if the generated visitor is still valid for this ast.go")
 )
 
 const usage = `Usage of visitorgen:
 
-go run go/visitorgen/main/main.go -input=/path/to/ast.go -output=/path/to/rewriter.go
+go run /path/to/visitorgen/main -input=/path/to/ast.go -output=/path/to/rewriter.go
 `
 
 func main() {
-	flag.Usage = func() {
-		os.Stderr.WriteString(usage)
-		os.Stderr.WriteString("\nOptions:\n")
-		flag.PrintDefaults()
-
-	}
+	defer exit.Recover()
+	flag.Usage = printUsage
 	flag.Parse()
 
 	if *inputFile == "" || *outputFile == "" {
-		fmt.Println("> " + *inputFile)
-		fmt.Println("> " + *outputFile)
-		panic("need input and output file")
+		printUsage()
+		exit.Return(1)
 	}
 
 	fs := token.NewFileSet()
 	file, err := parser.ParseFile(fs, *inputFile, nil, parser.DeclarationErrors)
 	if err != nil {
-		panic(err)
+		log.Error(err)
+		exit.Return(1)
 	}
 
 	astWalkResult := visitorgen.Walk(file)
@@ -64,49 +66,45 @@ func main() {
 	replacementMethods := visitorgen.EmitReplacementMethods(vd)
 	typeSwitch := visitorgen.EmitTypeSwitches(vd)
 
-	fw := newFileWriter(*outputFile)
-	defer fw.Close()
-
-	fw.writeln(fileHeader)
-	fw.writeln(replacementMethods)
-	fw.write(applyHeader)
-	fw.writeln(typeSwitch)
-	fw.writeln(fileFooter)
-}
-
-type fileWriter struct {
-	file *os.File
-}
-
-func newFileWriter(file string) *fileWriter {
-	f, err := os.Create(file)
-	if err != nil {
-		panic(err)
+	b := &bytes.Buffer{}
+	fmt.Fprint(b, fileHeader)
+	fmt.Fprintln(b)
+	fmt.Fprintln(b, replacementMethods)
+	fmt.Fprint(b, applyHeader)
+	fmt.Fprintln(b, typeSwitch)
+	fmt.Fprintln(b, fileFooter)
+
+	if *compare {
+		currentFile, err := ioutil.ReadFile(*outputFile)
+		if err != nil {
+			log.Error(err)
+			exit.Return(1)
+		}
+		if !bytes.Equal(b.Bytes(), currentFile) {
+			fmt.Println("rewriter needs to be re-generated: go generate " + *outputFile)
+			exit.Return(1)
+		}
+	} else {
+		err = ioutil.WriteFile(*outputFile, b.Bytes(), 0644)
+		if err != nil {
+			log.Error(err)
+			exit.Return(1)
+		}
 	}
-	return &fileWriter{file: f}
-}
 
-func (fw *fileWriter) writeln(s string) {
-	fw.write(s)
-	fw.write("\n")
-}
-
-func (fw *fileWriter) write(s string) {
-	_, err := fw.file.WriteString(s)
-	if err != nil {
-		panic(err)
-	}
 }
 
-func (fw *fileWriter) Close() {
-	fw.file.Close()
+func printUsage() {
+	os.Stderr.WriteString(usage)
+	os.Stderr.WriteString("\nOptions:\n")
+	flag.PrintDefaults()
 }
 
 const fileHeader = `// Code generated by visitorgen/main/main.go. DO NOT EDIT.
 
 package sqlparser
 
-//go:generate make visitor
+//go:generate go run visitorgen/main -input=ast.go -output=rewriter.go
 
 import (
 	"reflect"

misc/git/hooks/visitorgen

@@ -15,11 +15,4 @@
 
 # this script, which should run before committing code, makes sure that the visitor is re-generated when the ast changes
 
-make visitor REWRITER=tmp_rewriter.go
-if ! cmp -s "tmp_rewriter.go" "go/vt/sqlparser/rewriter.go"; then
-	echo "The ast.go has changed, but not rewriter.go"
-	echo "You should 'make visitor' to update the generated rewriter"
-	rm -f tmp_rewriter.go
-	exit 1
-fi
-rm -f tmp_rewriter.go
+go run ./go/vt/sqlparser/visitorgen/main -compareOnly=true -input=go/vt/sqlparser/ast.go -output=go/vt/sqlparser/rewriter.go