cli: streamline autostart ux (#2251)

This commit adds the following changes:

- autostart enable|disable => autostart set|unset
- autostart enable now accepts a more natual schedule format: <time> <days-of-week> <location>
- autostart show now shows configured timezone
- 🎉 automatic timezone detection across mac, windows, linux 🎉

Fixes #1647

coderd/util/tz/tz.go

@@ -0,0 +1,30 @@
+// Package tz includes utilities for cross-platform timezone/location detection.
+package tz
+
+import (
+	"os"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+var errNoEnvSet = xerrors.New("no env set")
+
+func locationFromEnv() (*time.Location, error) {
+	tzEnv, found := os.LookupEnv("TZ")
+	if !found {
+		return nil, errNoEnvSet
+	}
+
+	// TZ set but empty means UTC.
+	if tzEnv == "" {
+		return time.UTC, nil
+	}
+
+	loc, err := time.LoadLocation(tzEnv)
+	if err != nil {
+		return nil, xerrors.Errorf("load location from TZ env: %w", err)
+	}
+
+	return loc, nil
+}

coderd/util/tz/tz_darwin.go

@@ -0,0 +1,50 @@
+//go:build darwin
+
+package tz
+
+import (
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+const etcLocaltime = "/etc/localtime"
+const zoneInfoPath = "/var/db/timezone/zoneinfo/"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	lp, err := filepath.EvalSymlinks(etcLocaltime)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", etcLocaltime, err)
+	}
+
+	// On Darwin, /var/db/timezone/zoneinfo is also a symlink
+	realZoneInfoPath, err := filepath.EvalSymlinks(zoneInfoPath)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", zoneInfoPath, err)
+	}
+
+	stripped := strings.Replace(lp, realZoneInfoPath, "", -1)
+	stripped = strings.TrimPrefix(stripped, string(filepath.Separator))
+	loc, err = time.LoadLocation(stripped)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q guessed from %s: %w", stripped, lp, err)
+	}
+	return loc, nil
+}

coderd/util/tz/tz_linux.go

@@ -0,0 +1,44 @@
+//go:build linux
+
+package tz
+
+import (
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+const etcLocaltime = "/etc/localtime"
+const zoneInfoPath = "/usr/share/zoneinfo"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	lp, err := filepath.EvalSymlinks(etcLocaltime)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", etcLocaltime, err)
+	}
+
+	stripped := strings.Replace(lp, zoneInfoPath, "", -1)
+	stripped = strings.TrimPrefix(stripped, string(filepath.Separator))
+	loc, err = time.LoadLocation(stripped)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q guessed from %s: %w", stripped, lp, err)
+	}
+	return loc, nil
+}

coderd/util/tz/tz_test.go

@@ -0,0 +1,40 @@
+package tz_test
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/coderd/util/tz"
+)
+
+//nolint:paralleltest // Environment variables
+func Test_TimezoneIANA(t *testing.T) {
+	//nolint:paralleltest // t.Setenv
+	t.Run("Env", func(t *testing.T) {
+		t.Setenv("TZ", "Europe/Dublin")
+
+		zone, err := tz.TimezoneIANA()
+		assert.NoError(t, err)
+		if assert.NotNil(t, zone) {
+			assert.Equal(t, "Europe/Dublin", zone.String())
+		}
+	})
+
+	//nolint:paralleltest // UnsetEnv
+	t.Run("NoEnv", func(t *testing.T) {
+		oldEnv, found := os.LookupEnv("TZ")
+		if found {
+			require.NoError(t, os.Unsetenv("TZ"))
+			t.Cleanup(func() {
+				_ = os.Setenv("TZ", oldEnv)
+			})
+		}
+
+		zone, err := tz.TimezoneIANA()
+		assert.NoError(t, err)
+		assert.NotNil(t, zone)
+	})
+}

coderd/util/tz/tz_windows.go

@@ -0,0 +1,55 @@
+// go:build windows
+
+package tz
+
+import (
+	"os/exec"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+// cmdTimezone is a Powershell incantation that will return the system
+// time location in IANA format.
+const cmdTimezone = "[Windows.Globalization.Calendar,Windows.Globalization,ContentType=WindowsRuntime]::New().GetTimeZone()"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	// https://superuser.com/a/1584968
+	cmd := exec.Command("powershell.exe", "-NoLogo", "-NoProfile", "-NonInteractive")
+	// Powershell echoes its stdin so write a newline
+	cmd.Stdin = strings.NewReader(cmdTimezone + "\n")
+
+	outBytes, err := cmd.CombinedOutput()
+	if err != nil {
+		return nil, xerrors.Errorf("execute powershell command %q: %w", cmdTimezone, err)
+	}
+
+	outLines := strings.Split(string(outBytes), "\n")
+	if len(outLines) < 2 {
+		return nil, xerrors.Errorf("unexpected output from powershell command %q: %q", cmdTimezone, outLines)
+	}
+	// What we want is the second line of output
+	locStr := strings.TrimSpace(outLines[1])
+	loc, err = time.LoadLocation(locStr)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q from powershell: %w", locStr, err)
+	}
+
+	return loc, nil
+}