Adjust timezone logic

This commit adjusts the previous commit re. the new `ToTimeInDefaultLocationE` and related functions.

The functional change is that we don't default to any location if not provided from the caller.
This is in line with how `ToTime` worked before we started this, and even if the default behaviour may look weird in some cases, it will not break anything.

Most applications will want to use the new *InDefaultLocation functions and decide which default location to use:

```go
loc := time.Local
if config.Location != "" {
    loc = time.LoadLocation(config.Location)
}

t, err := StringToDateInDefaultLocation("2019-01-01", loc)

```

This commit also configure Travis to test on OSX and Windows in addition to Linux.

.travis.yml

@@ -8,9 +8,14 @@ go:
   - tip
 os:
   - linux
+  - osx
+  - windows
 matrix:
   allow_failures:
     - go: tip
+  exclude:
+    - os: windows
+      go: tip
   fast_finish: true
 script:
-  - make check
+  - if [[ "$TRAVIS_OS_NAME" == "windows" ]]; then go test -v -race ./...; else make check; fi

Makefile

@@ -1,15 +1,15 @@
 GOVERSION := $(shell go version | cut -d ' ' -f 3 | cut -d '.' -f 2)
 
-.PHONY: check fmt lint test test-race vet test-cover-html help
+.PHONY: check fmt test test-race vet test-cover-html help
 .DEFAULT_GOAL := help
 
-check: test-race fmt vet lint ## Run tests and linters
+check: test-race fmt vet ## Run tests and linters
 
 test: ## Run tests
 	go test ./...
 
 test-race: ## Run tests with race detector
-	go test -race ./...
+	go test -v -race ./...
 
 fmt: ## Run gofmt linter
 ifeq "$(GOVERSION)" "12"
@@ -20,12 +20,6 @@ ifeq "$(GOVERSION)" "12"
 	done
 endif
 
-lint: ## Run golint linter
-	@for d in `go list` ; do \
-		if [ "`golint $$d | tee /dev/stderr`" ]; then \
-			echo "^ golint errors!" && echo && exit 1; \
-		fi \
-	done
 
 vet: ## Run go vet linter
 	@if [ "`go vet | tee /dev/stderr`" ]; then \

cast.go

@@ -20,6 +20,14 @@ func ToTime(i interface{}) time.Time {
 	return v
 }
 
+// ToTimeInDefaultLocationE casts an empty interface to time.Time,
+// interpreting inputs without a timezone to be in the given location.
+// To fall back to the local timezone, use time.Local as the last argument.
+func ToTimeInDefaultLocation(i interface{}, location *time.Location) time.Time {
+	v, _ := ToTimeInDefaultLocationE(i, location)
+	return v
+}
+
 // ToDuration casts an interface to a time.Duration type.
 func ToDuration(i interface{}) time.Duration {
 	v, _ := ToDurationE(i)

cast_test.go

@@ -8,10 +8,12 @@ package cast
 import (
 	"fmt"
 	"html/template"
+	"path"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestToUintE(t *testing.T) {
@@ -1173,7 +1175,7 @@ func TestIndirectPointers(t *testing.T) {
 	assert.Equal(t, ToInt(z), 13)
 }
 
-func TestToTimeEE(t *testing.T) {
+func TestToTime(t *testing.T) {
 	tests := []struct {
 		input  interface{}
 		expect time.Time
@@ -1285,3 +1287,148 @@ func TestToDurationE(t *testing.T) {
 		assert.Equal(t, test.expect, v, errmsg)
 	}
 }
+
+func TestToTimeWithTimezones(t *testing.T) {
+
+	est, err := time.LoadLocation("EST")
+	require.NoError(t, err)
+
+	irn, err := time.LoadLocation("Iran")
+	require.NoError(t, err)
+
+	require.NoError(t, err)
+
+	// Test same local time in different timezones
+	utc2016 := time.Date(2016, time.January, 1, 3, 1, 0, 0, time.UTC)
+	est2016 := time.Date(2016, time.January, 1, 3, 1, 0, 0, est)
+	irn2016 := time.Date(2016, time.January, 1, 3, 1, 0, 0, irn)
+	loc2016 := time.Date(2016, time.January, 1, 3, 1, 0, 0, time.Local)
+
+	for i, format := range timeFormats {
+		format := format
+		if format.typ == timeFormatShort {
+			continue
+		}
+
+		nameBase := fmt.Sprintf("%d;timeFormatType=%d;%s", i, format.typ, format.format)
+
+		t.Run(path.Join(nameBase), func(t *testing.T) {
+			est2016str := est2016.Format(format.format)
+			loc2016str := loc2016.Format(format.format)
+
+			t.Run("without default location", func(t *testing.T) {
+				assert := require.New(t)
+				converted, err := ToTimeE(est2016str)
+				assert.NoError(err)
+				if format.hasNumericTimezone() {
+					assertTimeEqual(t, est2016, converted)
+					assertLocationEqual(t, est, converted.Location())
+				} else {
+					assertTimeEqual(t, utc2016, converted)
+					assertLocationEqual(t, time.UTC, converted.Location())
+				}
+			})
+
+			t.Run("local timezone without a default location", func(t *testing.T) {
+				assert := require.New(t)
+				converted, err := ToTimeE(loc2016str)
+				assert.NoError(err)
+				if format.hasAnyTimezone() {
+					// Local timezone strings can be either named or numeric and
+					// time.Parse connects the dots.
+					assertTimeEqual(t, loc2016, converted)
+					assertLocationEqual(t, time.Local, converted.Location())
+				} else {
+					assertTimeEqual(t, utc2016, converted)
+					assertLocationEqual(t, time.UTC, converted.Location())
+				}
+			})
+
+			t.Run("nil default location", func(t *testing.T) {
+				assert := require.New(t)
+
+				converted, err := ToTimeInDefaultLocationE(est2016str, nil)
+				assert.NoError(err)
+				if format.hasNumericTimezone() {
+					assertTimeEqual(t, est2016, converted)
+					assertLocationEqual(t, est, converted.Location())
+				} else {
+					assertTimeEqual(t, utc2016, converted)
+					assertLocationEqual(t, time.UTC, converted.Location())
+				}
+
+			})
+
+			t.Run("default location not UTC", func(t *testing.T) {
+				assert := require.New(t)
+
+				converted, err := ToTimeInDefaultLocationE(est2016str, irn)
+				assert.NoError(err)
+				if format.hasNumericTimezone() {
+					assertTimeEqual(t, est2016, converted)
+					assertLocationEqual(t, est, converted.Location())
+				} else {
+					assertTimeEqual(t, irn2016, converted)
+					assertLocationEqual(t, irn, converted.Location())
+				}
+			})
+
+			t.Run("time in the local timezone default location not UTC", func(t *testing.T) {
+				assert := require.New(t)
+
+				converted, err := ToTimeInDefaultLocationE(loc2016str, irn)
+				assert.NoError(err)
+
+				if format.hasNumericTimezone() {
+					assertTimeEqual(t, loc2016, converted)
+					assertLocationEqual(t, time.Local, converted.Location())
+				} else {
+					assertTimeEqual(t, irn2016, converted)
+					assertLocationEqual(t, irn, converted.Location())
+				}
+			})
+		})
+	}
+}
+
+func assertTimeEqual(t *testing.T, expected, actual time.Time) {
+	t.Helper()
+	require.True(t, expected.Equal(actual), fmt.Sprintf("expected\n%s\ngot\n%s", expected, actual))
+	format := "2006-01-02 15:04:05.999999999 -0700"
+	require.Equal(t, expected.Format(format), actual.Format(format))
+}
+
+func assertLocationEqual(t *testing.T, expected, actual *time.Location) {
+	t.Helper()
+	require.True(t, locationEqual(expected, actual), fmt.Sprintf("Expected location '%s', got '%s'", expected, actual))
+}
+
+func locationEqual(a, b *time.Location) bool {
+	// A note about comparing time.Locations:
+	//   - can't only compare pointers
+	//   - can't compare loc.String() because locations with the same
+	//     name can have different offsets
+	//   - can't use reflect.DeepEqual because time.Location has internal
+	//     caches
+
+	if a == b {
+		return true
+	} else if a == nil || b == nil {
+		return false
+	}
+
+	// Check if they're equal by parsing times with a format that doesn't
+	// include a timezone, which will interpret it as being a local time in
+	// the given zone, and comparing the resulting local times.
+	tA, err := time.ParseInLocation("2006-01-02", "2016-01-01", a)
+	if err != nil {
+		return false
+	}
+
+	tB, err := time.ParseInLocation("2006-01-02", "2016-01-01", b)
+	if err != nil {
+		return false
+	}
+
+	return tA.Equal(tB)
+}

caste.go

@@ -20,13 +20,20 @@ var errNegativeNotAllowed = errors.New("unable to cast negative value")
 
 // ToTimeE casts an interface to a time.Time type.
 func ToTimeE(i interface{}) (tim time.Time, err error) {
+	return ToTimeInDefaultLocationE(i, nil)
+}
+
+// ToTimeInDefaultLocationE casts an empty interface to time.Time,
+// interpreting inputs without a timezone to be in the given location.
+// To fall back to the local timezone, use time.Local as the last argument.
+func ToTimeInDefaultLocationE(i interface{}, location *time.Location) (tim time.Time, err error) {
 	i = indirect(i)
 
 	switch v := i.(type) {
 	case time.Time:
 		return v, nil
 	case string:
-		return StringToDate(v)
+		return StringToDateInDefaultLocation(v, location)
 	case int:
 		return time.Unix(int64(v), 0), nil
 	case int64:
@@ -1204,43 +1211,97 @@ func ToDurationSliceE(i interface{}) ([]time.Duration, error) {
 // predefined list of formats.  If no suitable format is found, an error is
 // returned.
 func StringToDate(s string) (time.Time, error) {
-	return parseDateWith(s, []string{
+	return parseDateWith(s, nil, timeFormats)
-		time.RFC3339,
+}
-		"2006-01-02T15:04:05", // iso8601 without timezone
+
-		time.RFC1123Z,
+// StringToDateInDefaultLocation to parse a string into a time.Time type using a
-		time.RFC1123,
+// predefined list of formats, interpreting inputs without a timezone to be in
-		time.RFC822Z,
+// the given location.
-		time.RFC822,
+// To fall back to the local timezone, use time.Local as the last argument.
-		time.RFC850,
+func StringToDateInDefaultLocation(s string, location *time.Location) (time.Time, error) {
-		time.ANSIC,
+	return parseDateWith(s, location, timeFormats)
-		time.UnixDate,
+}
-		time.RubyDate,
+
-		"2006-01-02 15:04:05.999999999 -0700 MST", // Time.String()
+func parseDateWith(s string, location *time.Location, formats []timeFormat) (d time.Time, e error) {
-		"2006-01-02",
+	for _, format := range formats {
-		"02 Jan 2006",
+		if d, e = time.Parse(format.format, s); e == nil {
-		"2006-01-02T15:04:05-0700", // RFC3339 without timezone hh:mm colon
+
-		"2006-01-02 15:04:05 -07:00",
+			// Some time formats have a zone name, but no offset, so it gets
-		"2006-01-02 15:04:05 -0700",
+			// put in that zone name (not the default one passed in to us), but
-		"2006-01-02 15:04:05Z07:00", // RFC3339 without T
+			// without that zone's offset. So set the location manually.
-		"2006-01-02 15:04:05Z0700",  // RFC3339 without T or timezone hh:mm colon
+			// Note that we only do this when we get a location in the new *InDefaultLocation
-		"2006-01-02 15:04:05",
+			// variants to avoid breaking existing behaviour in ToTime, however
-		time.Kitchen,
+			// weird that existing behaviour may be.
-		time.Stamp,
+			if location != nil && !format.hasNumericTimezone() {
-		time.StampMilli,
+				year, month, day := d.Date()
-		time.StampMicro,
+				hour, min, sec := d.Clock()
-		time.StampNano,
+				d = time.Date(year, month, day, hour, min, sec, d.Nanosecond(), location)
-	})
 			}
 
-func parseDateWith(s string, dates []string) (d time.Time, e error) {
-	for _, dateType := range dates {
-		if d, e = time.Parse(dateType, s); e == nil {
 			return
 		}
 	}
 	return d, fmt.Errorf("unable to parse date: %s", s)
 }
 
+type timeFormatType int
+
+const (
+	timeFormatShort timeFormatType = iota // time or date only, no timezone
+	timeFormatNoTimezone
+
+	// All below have some kind of timezone information, a name and/or offset.
+	timeFormatNamedTimezone
+
+	// All below have what we consider to be solid timezone information.
+	timeFormatNumericAndNamedTimezone
+	timeFormatNumericTimezone
+)
+
+type timeFormat struct {
+	format string
+	typ    timeFormatType
+}
+
+func (f timeFormat) hasNumericTimezone() bool {
+	return f.typ >= timeFormatNumericAndNamedTimezone
+}
+
+func (f timeFormat) hasAnyTimezone() bool {
+	return f.typ >= timeFormatNamedTimezone
+}
+
+var (
+	timeFormats = []timeFormat{
+		{time.RFC3339, timeFormatNumericTimezone},
+		{"2006-01-02T15:04:05", timeFormatNoTimezone}, // iso8601 without timezone
+		{time.RFC1123Z, timeFormatNumericTimezone},
+		{time.RFC1123, timeFormatNamedTimezone},
+		{time.RFC822Z, timeFormatNumericTimezone},
+		{time.RFC822, timeFormatNamedTimezone},
+		{time.RFC850, timeFormatNamedTimezone},
+		{"2006-01-02 15:04:05.999999999 -0700 MST", timeFormatNumericAndNamedTimezone}, // Time.String()
+		{"2006-01-02T15:04:05-0700", timeFormatNumericTimezone},                        // RFC3339 without timezone hh:mm colon
+		{"2006-01-02 15:04:05Z0700", timeFormatNumericTimezone},                        // RFC3339 without T or timezone hh:mm colon
+		{"2006-01-02 15:04:05", timeFormatNoTimezone},
+		{time.ANSIC, timeFormatNoTimezone},
+		// Must try RubyDate before UnixDate, see:
+		// https://github.com/golang/go/issues/32358
+		{time.RubyDate, timeFormatNumericTimezone},
+		{time.UnixDate, timeFormatNamedTimezone},
+		{"2006-01-02 15:04:05Z07:00", timeFormatNumericTimezone},
+		{"2006-01-02", timeFormatShort},
+		{"02 Jan 2006", timeFormatShort},
+		{"2006-01-02 15:04:05 -07:00", timeFormatNumericTimezone},
+		{"2006-01-02 15:04:05 -0700", timeFormatNumericTimezone},
+		{time.Kitchen, timeFormatShort},
+		{time.Stamp, timeFormatShort},
+		{time.StampMilli, timeFormatShort},
+		{time.StampMicro, timeFormatShort},
+		{time.StampNano, timeFormatShort},
+	}
+)
+
 // jsonStringToObject attempts to unmarshall a string as JSON into
 // the object passed as pointer.
 func jsonStringToObject(s string, v interface{}) error {