Stop startup when a setting does not parse (closes #219)

config.New read the number and true/false settings with viper's
GetInt, GetFloat64 and GetBool. These return zero or false for a value
that does not parse, so a typo silently changed how the server ran.

config.New now parses these settings with strconv. It also checks that
MESSAGE_MAX_AGE, QUEUE_MAX_AGE and SESSION_IDLE_TIMEOUT are valid Go
durations. A value that does not parse makes config.New return an
error naming the setting and its value, and startup stops. Unset
settings keep their defaults.

Model: opus-5-5

internal/config/config.go

@@ -3,8 +3,11 @@ package config
 
 import (
 	"errors"
+	"fmt"
 	"log/slog"
 	"os"
+	"strconv"
+	"time"
 
 	"github.com/spf13/viper"
 	"go.uber.org/fx"
@@ -63,6 +66,8 @@ type Config struct {
 }
 
 // New creates a new Config by reading from files and environment variables.
+// It returns an error when a number, true/false or duration setting does
+// not parse.
 func New(
 	_ fx.Lifecycle, params Params,
 ) (*Config, error) {
@@ -107,29 +112,27 @@ func New(
 
 	cfg := &Config{
 		DBURL:              viper.GetString("DBURL"),
-		Debug:              viper.GetBool("DEBUG"),
-		Port:               viper.GetInt("PORT"),
 		SentryDSN:          viper.GetString("SENTRY_DSN"),
-		MaintenanceMode:    viper.GetBool("MAINTENANCE_MODE"),
 		MetricsUsername:    viper.GetString("METRICS_USERNAME"),
 		MetricsPassword:    viper.GetString("METRICS_PASSWORD"),
 		MessageMaxAge:      viper.GetString("MESSAGE_MAX_AGE"),
-		MaxMessageSize:     viper.GetInt("MAX_MESSAGE_SIZE"),
 		QueueMaxAge:        viper.GetString("QUEUE_MAX_AGE"),
 		MOTD:               viper.GetString("MOTD"),
 		ServerName:         viper.GetString("SERVER_NAME"),
 		FederationKey:      viper.GetString("FEDERATION_KEY"),
 		SessionIdleTimeout: viper.GetString("SESSION_IDLE_TIMEOUT"),
-		HashcashBits:       viper.GetInt("NEOIRC_HASHCASH_BITS"),
 		OperName:           viper.GetString("NEOIRC_OPER_NAME"),
 		OperPassword:       viper.GetString("NEOIRC_OPER_PASSWORD"),
-		LoginRateLimit:     viper.GetFloat64("LOGIN_RATE_LIMIT"),
-		LoginRateBurst:     viper.GetInt("LOGIN_RATE_BURST"),
 		IRCListenAddr:      viper.GetString("IRC_LISTEN_ADDR"),
 		log:                log,
 		params:             &params,
 	}
 
+	err = parseSettings(cfg)
+	if err != nil {
+		return nil, err
+	}
+
 	// Viper counts an empty environment variable as unset, but an
 	// empty IRC_LISTEN_ADDR must turn the IRC listener off.
 	ircListenAddr, set := os.LookupEnv("IRC_LISTEN_ADDR")
@@ -144,3 +147,68 @@ func New(
 
 	return cfg, nil
 }
+
+// parseSettings reads the number and true/false settings into cfg and
+// checks that each duration setting is a valid Go duration. Its error
+// names each setting whose value does not parse.
+func parseSettings(cfg *Config) error {
+	return errors.Join(
+		parseInt("PORT", &cfg.Port),
+		parseInt("MAX_MESSAGE_SIZE", &cfg.MaxMessageSize),
+		parseInt("NEOIRC_HASHCASH_BITS", &cfg.HashcashBits),
+		parseInt("LOGIN_RATE_BURST", &cfg.LoginRateBurst),
+		parseFloat("LOGIN_RATE_LIMIT", &cfg.LoginRateLimit),
+		parseBool("DEBUG", &cfg.Debug),
+		parseBool("MAINTENANCE_MODE", &cfg.MaintenanceMode),
+		checkDuration("MESSAGE_MAX_AGE", cfg.MessageMaxAge),
+		checkDuration("QUEUE_MAX_AGE", cfg.QueueMaxAge),
+		checkDuration("SESSION_IDLE_TIMEOUT", cfg.SessionIdleTimeout),
+	)
+}
+
+// parseInt sets *value to the setting key read as a whole number.
+func parseInt(key string, value *int) error {
+	parsed, err := strconv.Atoi(viper.GetString(key))
+	if err != nil {
+		return fmt.Errorf("cannot parse %s: %w", key, err)
+	}
+
+	*value = parsed
+
+	return nil
+}
+
+// parseFloat sets *value to the setting key read as a decimal number.
+func parseFloat(key string, value *float64) error {
+	parsed, err := strconv.ParseFloat(viper.GetString(key), 64)
+	if err != nil {
+		return fmt.Errorf("cannot parse %s: %w", key, err)
+	}
+
+	*value = parsed
+
+	return nil
+}
+
+// parseBool sets *value to the setting key read as true or false.
+func parseBool(key string, value *bool) error {
+	parsed, err := strconv.ParseBool(viper.GetString(key))
+	if err != nil {
+		return fmt.Errorf("cannot parse %s: %w", key, err)
+	}
+
+	*value = parsed
+
+	return nil
+}
+
+// checkDuration returns an error naming the setting key when value is
+// not a valid Go duration.
+func checkDuration(key, value string) error {
+	_, err := time.ParseDuration(value)
+	if err != nil {
+		return fmt.Errorf("cannot parse %s: %w", key, err)
+	}
+
+	return nil
+}

internal/config/config_test.go

@@ -2,6 +2,7 @@ package config_test
 
 import (
 	"os"
+	"strings"
 	"testing"
 	"time"
 
@@ -10,7 +11,8 @@ import (
 	"sneak.berlin/go/neoirc/internal/logger"
 )
 
-func newConfig(t *testing.T) *config.Config {
+// loadConfig runs config.New and returns its result.
+func loadConfig(t *testing.T) (*config.Config, error) {
 	t.Helper()
 
 	globs := &globals.Globals{
@@ -24,9 +26,15 @@ func newConfig(t *testing.T) *config.Config {
 		t.Fatal(err)
 	}
 
-	cfg, err := config.New(
+	return config.New(
 		nil, config.Params{Globals: globs, Logger: log},
 	)
+}
+
+func newConfig(t *testing.T) *config.Config {
+	t.Helper()
+
+	cfg, err := loadConfig(t)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -34,6 +42,137 @@ func newConfig(t *testing.T) *config.Config {
 	return cfg
 }
 
+func TestUnsetSettingsKeepDefaults(t *testing.T) {
+	// Viper counts an empty environment variable as unset.
+	t.Setenv("PORT", "")
+	t.Setenv("MAX_MESSAGE_SIZE", "")
+	t.Setenv("NEOIRC_HASHCASH_BITS", "")
+	t.Setenv("LOGIN_RATE_BURST", "")
+	t.Setenv("LOGIN_RATE_LIMIT", "")
+	t.Setenv("DEBUG", "")
+	t.Setenv("MAINTENANCE_MODE", "")
+	t.Setenv("MESSAGE_MAX_AGE", "")
+	t.Setenv("QUEUE_MAX_AGE", "")
+	t.Setenv("SESSION_IDLE_TIMEOUT", "")
+
+	// Each duration setting defaults to 30 days.
+	const thirtyDays = "720h"
+
+	want := settings{
+		Port:               8080,
+		MaxMessageSize:     4096,
+		HashcashBits:       20,
+		LoginRateBurst:     5,
+		LoginRateLimit:     1,
+		Debug:              false,
+		MaintenanceMode:    false,
+		MessageMaxAge:      thirtyDays,
+		QueueMaxAge:        thirtyDays,
+		SessionIdleTimeout: thirtyDays,
+	}
+
+	got := settingsOf(newConfig(t))
+	if got != want {
+		t.Errorf("settings = %+v, want %+v", got, want)
+	}
+}
+
+func TestValidSettingsAreUsed(t *testing.T) {
+	t.Setenv("PORT", "9000")
+	t.Setenv("MAX_MESSAGE_SIZE", "1024")
+	t.Setenv("NEOIRC_HASHCASH_BITS", "0")
+	t.Setenv("LOGIN_RATE_BURST", "10")
+	t.Setenv("LOGIN_RATE_LIMIT", "0.5")
+	t.Setenv("DEBUG", "true")
+	t.Setenv("MAINTENANCE_MODE", "true")
+	t.Setenv("MESSAGE_MAX_AGE", "24h")
+	t.Setenv("QUEUE_MAX_AGE", "1h30m")
+	t.Setenv("SESSION_IDLE_TIMEOUT", "0")
+
+	want := settings{
+		Port:               9000,
+		MaxMessageSize:     1024,
+		HashcashBits:       0,
+		LoginRateBurst:     10,
+		LoginRateLimit:     0.5,
+		Debug:              true,
+		MaintenanceMode:    true,
+		MessageMaxAge:      "24h",
+		QueueMaxAge:        "1h30m",
+		SessionIdleTimeout: "0",
+	}
+
+	got := settingsOf(newConfig(t))
+	if got != want {
+		t.Errorf("settings = %+v, want %+v", got, want)
+	}
+}
+
+// settings holds the Config fields whose settings config.New parses.
+type settings struct {
+	Port               int
+	MaxMessageSize     int
+	HashcashBits       int
+	LoginRateBurst     int
+	LoginRateLimit     float64
+	Debug              bool
+	MaintenanceMode    bool
+	MessageMaxAge      string
+	QueueMaxAge        string
+	SessionIdleTimeout string
+}
+
+func settingsOf(cfg *config.Config) settings {
+	return settings{
+		Port:               cfg.Port,
+		MaxMessageSize:     cfg.MaxMessageSize,
+		HashcashBits:       cfg.HashcashBits,
+		LoginRateBurst:     cfg.LoginRateBurst,
+		LoginRateLimit:     cfg.LoginRateLimit,
+		Debug:              cfg.Debug,
+		MaintenanceMode:    cfg.MaintenanceMode,
+		MessageMaxAge:      cfg.MessageMaxAge,
+		QueueMaxAge:        cfg.QueueMaxAge,
+		SessionIdleTimeout: cfg.SessionIdleTimeout,
+	}
+}
+
+func TestUnparseableSettingStopsStartup(t *testing.T) {
+	tests := []struct {
+		key   string
+		value string
+	}{
+		{key: "PORT", value: "80a"},
+		{key: "MAX_MESSAGE_SIZE", value: "4k"},
+		{key: "NEOIRC_HASHCASH_BITS", value: "twenty"},
+		{key: "LOGIN_RATE_BURST", value: "five"},
+		{key: "LOGIN_RATE_LIMIT", value: "fast"},
+		{key: "DEBUG", value: "yes"},
+		{key: "MAINTENANCE_MODE", value: "on"},
+		{key: "MESSAGE_MAX_AGE", value: "30d"},
+		{key: "QUEUE_MAX_AGE", value: "720"},
+		{key: "SESSION_IDLE_TIMEOUT", value: "a month"},
+	}
+
+	for _, test := range tests {
+		t.Run(test.key, func(t *testing.T) {
+			t.Setenv(test.key, test.value)
+
+			_, err := loadConfig(t)
+			if err == nil {
+				t.Fatalf("%s=%q: got no error", test.key, test.value)
+			}
+
+			msg := err.Error()
+			if !strings.Contains(msg, test.key) ||
+				!strings.Contains(msg, test.value) {
+				t.Errorf("error %q does not name %s and %q",
+					msg, test.key, test.value)
+			}
+		})
+	}
+}
+
 func TestIRCListenAddrUnsetKeepsDefault(t *testing.T) {
 	// t.Setenv puts back whatever value was there after the test.
 	t.Setenv("IRC_LISTEN_ADDR", "")