feat(coderd/database/dbtestutil): set default database timezone to non-UTC in unit tests (#9672)

- Adds dbtestutil.WithTimezone(tz) to allow setting the timezone for a test database.
- Modifies our test database setup code to pick a consistently weird timezone for the database.
- Adds the facility randtz.Name() to pick a random timezone which is consistent across subtests (via sync.Once).
- Adds a linter rule to warn against setting the test database timezone to UTC.

coderd/database/dbtestutil/db.go

@@ -3,7 +3,10 @@ package dbtestutil
 import (
 	"context"
 	"database/sql"
+	"fmt"
+	"net/url"
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -19,9 +22,27 @@ func WillUsePostgres() bool {
 	return os.Getenv("DB") != ""
 }
 
-func NewDB(t testing.TB) (database.Store, pubsub.Pubsub) {
+type options struct {
+	fixedTimezone string
+}
+
+type Option func(*options)
+
+// WithTimezone sets the database to the defined timezone.
+func WithTimezone(tz string) Option {
+	return func(o *options) {
+		o.fixedTimezone = tz
+	}
+}
+
+func NewDB(t testing.TB, opts ...Option) (database.Store, pubsub.Pubsub) {
 	t.Helper()
 
+	var o options
+	for _, opt := range opts {
+		opt(&o)
+	}
+
 	db := dbfake.New()
 	ps := pubsub.NewInMemory()
 	if WillUsePostgres() {
@@ -35,6 +56,19 @@ func NewDB(t testing.TB) (database.Store, pubsub.Pubsub) {
 			require.NoError(t, err)
 			t.Cleanup(closePg)
 		}
+
+		if o.fixedTimezone == "" {
+			// To make sure we find timezone-related issues, we set the timezone
+			// of the database to a non-UTC one.
+			// The below was picked due to the following properties:
+			// - It has a non-UTC offset
+			// - It has a fractional hour UTC offset
+			// - It includes a daylight savings time component
+			o.fixedTimezone = "Canada/Newfoundland"
+		}
+		dbName := dbNameFromConnectionURL(t, connectionURL)
+		setDBTimezone(t, connectionURL, dbName, o.fixedTimezone)
+
 		sqlDB, err := sql.Open("postgres", connectionURL)
 		require.NoError(t, err)
 		t.Cleanup(func() {
@@ -51,3 +85,28 @@ func NewDB(t testing.TB) (database.Store, pubsub.Pubsub) {
 
 	return db, ps
 }
+
+// setRandDBTimezone sets the timezone of the database to the given timezone.
+// Note that the updated timezone only comes into effect on reconnect, so we
+// create our own connection for this and close the DB after we're done.
+func setDBTimezone(t testing.TB, dbURL, dbname, tz string) {
+	t.Helper()
+
+	sqlDB, err := sql.Open("postgres", dbURL)
+	require.NoError(t, err)
+	defer func() {
+		_ = sqlDB.Close()
+	}()
+
+	// nolint: gosec // This unfortunately does not work with placeholders.
+	_, err = sqlDB.Exec(fmt.Sprintf("ALTER DATABASE %s SET TIMEZONE TO %q", dbname, tz))
+	require.NoError(t, err, "failed to set timezone for database")
+}
+
+// dbNameFromConnectionURL returns the database name from the given connection URL,
+// where connectionURL is of the form postgres://user:pass@host:port/dbname
+func dbNameFromConnectionURL(t testing.TB, connectionURL string) string {
+	u, err := url.Parse(connectionURL)
+	require.NoError(t, err)
+	return strings.TrimPrefix(u.Path, "/")
+}