Add --lowercase option to map column names to lowercase struct names (#3675)

* Add --lowercase option to map column names to lowercase struct names

By default, each column name maps to a struct field preserving the original case.
If --lowercase is specified the resulting struct fields will always be lowercase.

samples/go/csv/csv-import/importer.go

@@ -36,6 +36,7 @@ func main() {
 	// https://blog.golang.org/strings
 	delimiter := flag.String("delimiter", ",", "field delimiter for csv file, must be exactly one character long.")
 	header := flag.String("header", "", "header row. If empty, we'll use the first row of the file")
+	lowercase := flag.Bool("lowercase", false, "convert column names to lowercase (otherwise preserve the case in the resulting struct fields)")
 	name := flag.String("name", "Row", "struct name. The user-visible name to give to the struct type that will hold each row of data.")
 	columnTypes := flag.String("column-types", "", "a comma-separated list of types representing the desired type of each column. if absent all types default to be String")
 	pathDescription := "noms path to blob to import"
@@ -146,6 +147,11 @@ func main() {
 	} else {
 		headers = strings.Split(*header, ",")
 	}
+	if *lowercase {
+		for i, _ := range headers {
+			headers[i] = strings.ToLower(headers[i])
+		}
+	}
 
 	uniqueHeaders := make(map[string]bool)
 	for _, header := range headers {

samples/go/csv/csv-import/importer_test.go

@@ -49,7 +49,11 @@ func (s *testSuite) TearDownTest() {
 }
 
 func writeCSV(w io.Writer) {
-	_, err := io.WriteString(w, "year,a,b,c\n")
+	writeCSVWithHeader(w, "year,a,b,c\n")
+}
+
+func writeCSVWithHeader(w io.Writer, header string) {
+	_, err := io.WriteString(w, header)
 	d.Chk.NoError(err)
 	for i := 0; i < TEST_DATA_SIZE; i++ {
 		_, err = io.WriteString(w, fmt.Sprintf("%d,a%d,%d,%d\n", TEST_YEAR+i%3, i, i, i*2))
@@ -119,6 +123,40 @@ func (s *testSuite) TestCSVImporter() {
 	validateList(s, ds.HeadValue().(types.List))
 }
 
+func (s *testSuite) TestCSVImporterLowercase() {
+	input, err := ioutil.TempFile(s.TempDir, "")
+	d.Chk.NoError(err)
+	defer input.Close()
+	writeCSVWithHeader(input, "YeAr,a,B,c\n")
+	defer os.Remove(input.Name())
+
+	setName := "csv"
+	dataspec := spec.CreateValueSpecString("nbs", s.DBDir, setName)
+	stdout, stderr := s.MustRun(main, []string{"--no-progress", "--lowercase", "--column-types", TEST_FIELDS, input.Name(), dataspec})
+	s.Equal("", stdout)
+	s.Equal("", stderr)
+
+	db := datas.NewDatabase(nbs.NewLocalStore(s.DBDir, clienttest.DefaultMemTableSize))
+	defer os.RemoveAll(s.DBDir)
+	defer db.Close()
+	ds := db.GetDataset(setName)
+
+	validateList(s, ds.HeadValue().(types.List))
+}
+
+func (s *testSuite) TestCSVImporterLowercaseDuplicate() {
+	input, err := ioutil.TempFile(s.TempDir, "")
+	d.Chk.NoError(err)
+	defer input.Close()
+	writeCSVWithHeader(input, "YeAr,a,B,year\n")
+	defer os.Remove(input.Name())
+
+	setName := "csv"
+	dataspec := spec.CreateValueSpecString("nbs", s.DBDir, setName)
+	_, stderr, _ := s.Run(main, []string{"--no-progress", "--lowercase", "--column-types", TEST_FIELDS, input.Name(), dataspec})
+	s.Contains(stderr, "must be unique")
+}
+
 func (s *testSuite) TestCSVImporterFromBlob() {
 	test := func(pathFlag string) {
 		defer os.RemoveAll(s.DBDir)