printLoadedConf modified to only print explicitly set config values (via env or config file)

internal/config/debug.go

@@ -24,17 +24,21 @@ func printEnv() {
 	}
 }
 
-// printLoadedConfig logs every key Viper has loaded, with its value and type,
+// printLoadedConfig logs every key set by the config file or an environment
-// at debug level.
+// variable (see isExplicitlySet), with its value and type, at debug level.
 func printLoadedConfig() {
 	slog.Debug("Loaded config:")
 	keys := viper.AllKeys()
 	for i := range keys {
 		k := keys[i]
+		if isExplicitlySet(k) {
 			v := viper.Get(k)
 			t := reflect.TypeOf(v)
 			slog.Debug(
-			"\t" + k + " = " + fmt.Sprintf("%#v", v) + " <" + t.Kind().String() + ">")
+				"\t" + k + " = " + fmt.Sprintf("%#v", v) +
+					" <" + t.Kind().String() + ">",
+			)
+		}
 	}
 }
 

internal/config/load.go

@@ -3,12 +3,35 @@ package config
 import (
 	"fmt"
 	"log/slog"
+	"os"
 	"strings"
 
 	"github.com/joho/godotenv"
 	"github.com/spf13/viper"
 )
 
+// envKeyReplacer turns a dotted key into its environment variable's suffix
+// (logging.level to LOGGING_LEVEL, once upper-cased).
+var envKeyReplacer = strings.NewReplacer(".", "_")
+
+// envVarName returns the environment variable that sets key, e.g.
+// JOBSEARCH_LOGGING_LEVEL for logging.level.
+func envVarName(key string) string {
+	return EnvPrefix + "_" + strings.ToUpper(envKeyReplacer.Replace(key))
+}
+
+// isExplicitlySet reports whether key's value in Viper was set by the config
+// file or by its environment variable, rather than coming from its default.
+// As Viper does, it ignores an empty environment variable. Values set with
+// viper.Set (e.g. by StoreValue) are not counted.
+func isExplicitlySet(key string) bool {
+	if viper.InConfig(key) {
+		return true
+	}
+	value, ok := os.LookupEnv(envVarName(key))
+	return ok && value != ""
+}
+
 // loadEnv loads environment variables from a .env file in the working
 // directory.
 func loadEnv() error {
@@ -37,7 +60,7 @@ func loadConfig(cfgFile string) error {
 	LoadDefaultConfig()
 
 	viper.SetEnvPrefix(EnvPrefix)
-	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	viper.SetEnvKeyReplacer(envKeyReplacer)
 	viper.AutomaticEnv() // read in environment variables that match
 
 	err := viper.ReadInConfig()

internal/config/load_test.go

@@ -7,6 +7,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/spf13/viper"
 )
 
 // initDir makes a temp working directory holding a .env file (if env is not
@@ -167,3 +169,89 @@ func TestInitEnvOverride(t *testing.T) {
 		t.Errorf("FTSMock.Interval = %v; want 45s from the environment", conf.Sources.FTSMock.Interval)
 	}
 }
+
+func TestEnvVarName(t *testing.T) {
+	tests := map[string]string{
+		"logging.level":                             "JOBSEARCH_LOGGING_LEVEL",
+		"sources.fts_mock.interval":                 "JOBSEARCH_SOURCES_FTS_MOCK_INTERVAL",
+		"server.websocket.connection_limit.enabled": "JOBSEARCH_SERVER_WEBSOCKET_CONNECTION_LIMIT_ENABLED",
+	}
+	for key, want := range tests {
+		if got := envVarName(key); got != want {
+			t.Errorf("envVarName(%q) = %q; want %q", key, got, want)
+		}
+	}
+}
+
+// explicitConfigYAML sets a top-level and a nested key in a config file.
+const explicitConfigYAML = `logging:
+  level: info
+server:
+  websocket:
+    connection_limit:
+      enabled: true
+`
+
+// loadExplicit sets up Viper as Init does, with the defaults, the config
+// file explicitConfigYAML and the JOBSEARCH_* environment variables.
+func loadExplicit(t *testing.T) {
+	t.Helper()
+	resetViper(t)
+	LoadDefaultConfig()
+	viper.SetEnvPrefix(EnvPrefix)
+	viper.SetEnvKeyReplacer(envKeyReplacer)
+	viper.AutomaticEnv()
+	viper.SetConfigType("yaml")
+	if err := viper.ReadConfig(strings.NewReader(explicitConfigYAML)); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// A key is explicitly set by the config file or a non-empty environment
+// variable, not by its default or viper.Set.
+func TestIsExplicitlySet(t *testing.T) {
+	t.Setenv("JOBSEARCH_DATABASE_FILE", "/tmp/js.db")
+	t.Setenv("JOBSEARCH_LOGGING_FILE", "")
+	loadExplicit(t)
+	viper.Set("sources.sleeper.enabled", true)
+
+	tests := map[string]bool{
+		"logging.level": true, // config file
+		"server.websocket.connection_limit.enabled": true, // nested, config file
+		"database.file":                           true,  // environment
+		"logging.file":                            false, // empty environment variable
+		"sources.sleeper.interval":                false, // default only
+		"sources.sleeper.enabled":                 false, // viper.Set
+		"server.websocket.connection_limit.burst": false, // default, beside a set key
+	}
+	for key, want := range tests {
+		if got := isExplicitlySet(key); got != want {
+			t.Errorf("isExplicitlySet(%q) = %v; want %v", key, got, want)
+		}
+	}
+}
+
+// printLoadedConfig logs only the keys set by the config file or the
+// environment.
+func TestPrintLoadedConfig(t *testing.T) {
+	t.Setenv("JOBSEARCH_DATABASE_FILE", "/tmp/js.db")
+	loadExplicit(t)
+	logs := captureLogs(t, slog.LevelDebug)
+	printLoadedConfig()
+
+	out := logs.String()
+	for _, want := range []string{
+		`logging.level = \"info\" <string>`,
+		`server.websocket.connection_limit.enabled = true <bool>`,
+		`database.file = \"/tmp/js.db\" <string>`,
+	} {
+		if !strings.Contains(out, want) {
+			t.Errorf("missing %q in:\n%s", want, out)
+		}
+	}
+	for _, unwanted := range []string{"sources.", "logging.file", "connection_limit.burst"} {
+		if strings.Contains(out, unwanted) {
+			t.Errorf("logged default key %q:\n%s", unwanted, out)
+		}
+	}
+}