schema: add small tool to standardize JSON formatting

schema/generator

@@ -31,6 +31,8 @@ if [ ! -f $GENDOC ]; then
     exit 1
 fi
 
+go run schema/jsonfmt.go $IN
+
 $GENDOC --f $IN --o $DOC
 
 # Though google-api-go-generator is a main, dex vendors the app using the same

schema/jsonfmt.go

@@ -0,0 +1,54 @@
+// +build ignore
+
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"io/ioutil"
+	"log"
+	"os"
+)
+
+func init() {
+	log.SetPrefix("fmtjson: ")
+	log.SetFlags(0)
+}
+
+func main() {
+	if len(os.Args) < 1 {
+		log.Fatal(`usage: go run jsonfmt.go [files...]
+
+This is a small utility that standardizes the formatting of JSON files.
+`)
+	}
+
+	for _, path := range os.Args[1:] {
+		data, err := ioutil.ReadFile(path)
+		if err != nil {
+			log.Fatalf("reading file %s: %v", path, err)
+		}
+
+		buff := new(bytes.Buffer)
+		if err := json.Indent(buff, data, "", "  "); err != nil {
+			if err, ok := err.(*json.SyntaxError); ok {
+				// Calculate line number and column of error.
+				data := data[:err.Offset]
+				lineNum := 1 + bytes.Count(data, []byte{'\n'})
+				lastIndex := bytes.LastIndex(data, []byte{'\n'})
+
+				colNum := err.Offset
+				if lastIndex > -1 {
+					colNum = int64(len(data) - lastIndex)
+				}
+				log.Fatalf("file %s: invalid json at line %d, column %d: %v", path, lineNum, colNum, err)
+			}
+
+			log.Fatalf("file %s: invalid json: %v", path, err)
+		}
+
+		if err := ioutil.WriteFile(path, buff.Bytes(), 0644); err != nil {
+			log.Fatalf("write file %s: %v", path, err)
+		}
+	}
+}