Add use_of_customfuncs.md

Also fix a couple lint issues by unexporting constants (that don't need to be exported)

customfuncs/datetime.go

@@ -114,8 +114,8 @@ func DateTimeLayoutToRFC3339(_ *transformctx.Ctx, datetime, layout, layoutTZ, fr
 }
 
 const (
-EpochUnitMilliseconds = "MILLISECOND"
-EpochUnitSeconds = "SECOND"
+epochUnitMilliseconds = "MILLISECOND"
+epochUnitSeconds = "SECOND"
 )
 
 // DateTimeToEpoch parses a 'datetime' string intelligently, and returns its epoch number. 'fromTZ'
@@ -131,9 +131,9 @@ func DateTimeToEpoch(_ *transformctx.Ctx, datetime, fromTZ, unit string) (string
 return "", err
 }
 switch unit {
-case EpochUnitMilliseconds:
+case epochUnitMilliseconds:
 return strconv.FormatInt(t.UnixNano()/int64(time.Millisecond), 10), nil
-case EpochUnitSeconds:
+case epochUnitSeconds:
 return strconv.FormatInt(t.Unix(), 10), nil
 default:
 return "", fmt.Errorf("unknown epoch unit '%s'", unit)
@@ -163,9 +163,9 @@ func EpochToDateTimeRFC3339(_ *transformctx.Ctx, epoch, unit string, tz ...strin
 }
 var t time.Time
 switch unit {
-case EpochUnitSeconds:
+case epochUnitSeconds:
 t = time.Unix(n, 0)
-case EpochUnitMilliseconds:
+case epochUnitMilliseconds:
 t = time.Unix(0, n*(int64(time.Millisecond)))
 default:
 return "", fmt.Errorf("unknown epoch unit '%s'", unit)

customfuncs/datetime_test.go

@@ -216,23 +216,23 @@ func TestDateTimeToEpoch(t *testing.T) {
 name: "empty datetime -> no op",
 datetime: "",
 fromTZ: "UTC",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 err: "",
 expected: "",
 },
 {
 name: "invalid datetime",
 datetime: "invalid",
 fromTZ: "UTC",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 err: "unable to parse 'invalid' in any supported date/time format",
 expected: "",
 },
 {
 name: "invalid fromTZ",
 datetime: "2020/09/22T12:34:56",
 fromTZ: "invalid",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 err: "unknown time zone invalid",
 expected: "",
 },
@@ -248,23 +248,23 @@ func TestDateTimeToEpoch(t *testing.T) {
 name: "datetime no tz; no fromTZ",
 datetime: "2020/09/22T12:34:56",
 fromTZ: "",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 err: "",
 expected: "1600778096000",
 },
 {
 name: "datetime no tz; with fromTZ",
 datetime: "2020/09/22T12:34:56",
 fromTZ: "America/Los_Angeles",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 err: "",
 expected: "1600803296",
 },
 {
 name: "datetime with tz; with fromTZ",
 datetime: "2020/09/22T12:34:56-05",
 fromTZ: "America/Los_Angeles",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 err: "",
 expected: "1600796096",
 },
@@ -295,31 +295,31 @@ func TestEpochToDateTimeRFC3339(t *testing.T) {
 {
 name: "empty epoch -> no op",
 epoch: "",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 tz: nil,
 err: "",
 expected: "",
 },
 {
 name: "more than one tz specified",
 epoch: "1234567",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 tz: []string{"UTC", "UTC"},
 err: "cannot specify tz argument more than once",
 expected: "",
 },
 {
 name: "invalid epoch",
 epoch: "invalid",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 tz: nil,
 err: `strconv.ParseInt: parsing "invalid": invalid syntax`,
 expected: "",
 },
 {
 name: "invalid tz",
 epoch: "12345",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 tz: []string{"invalid"},
 err: "unknown time zone invalid",
 expected: "",
@@ -335,15 +335,15 @@ func TestEpochToDateTimeRFC3339(t *testing.T) {
 {
 name: "no tz",
 epoch: "1234567890123",
-unit: EpochUnitMilliseconds,
+unit: epochUnitMilliseconds,
 tz: nil,
 err: "",
 expected: "2009-02-13T23:31:30Z",
 },
 {
 name: "with tz",
 epoch: "1234567890",
-unit: EpochUnitSeconds,
+unit: epochUnitSeconds,
 tz: []string{"America/Los_Angeles"},
 err: "",
 expected: "2009-02-13T15:31:30-08:00",