tools/govalidate: start of a frontend for tools/internal/parser

Parses the given file and reports parsing and validation errors.

tools/govalidate/govalidate.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"github.com/publicsuffix/list/tools/internal/parser"
+)
+
+func main() {
+	warnings := flag.Bool("with-warnings", false, "also print errors that were downgraded to warnings")
+	flag.Usage = func() {
+		fmt.Fprintf(flag.CommandLine.Output(), "Usage: %s [flags] pslfile\n", os.Args[0])
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+
+	if flag.NArg() != 1 {
+		flag.Usage()
+	}
+
+	file := flag.Arg(0)
+
+	bs, err := os.ReadFile(file)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Reading PSL file: %v", err)
+		os.Exit(1)
+	}
+
+	psl := parser.Parse(string(bs))
+
+	for _, err := range psl.Errors {
+		fmt.Println(err)
+	}
+	if *warnings {
+		for _, err := range psl.Warnings {
+			fmt.Println(err, "(ignored)")
+		}
+	}
+	if len(psl.Errors) > 0 {
+		os.Exit(1)
+	} else {
+		fmt.Printf("%q seems to be a valid PSL file.\n", file)
+	}
+}