Prevent a warning being printed when parsing config

cmd/bagel/root.go

@@ -128,7 +128,8 @@ func initConfig() {
 		viper.AddConfigPath(config.GetConfigDir())
 		viper.AddConfigPath(".")
 		viper.SetConfigName("bagel")
-		viper.SetConfigType("yaml")
+		// No SetConfigType: it would make viper match the extensionless "bagel"
+		// binary as a config file (see pkg/config.Load for the full rationale).
 	}
 
 	viper.SetEnvPrefix("BAGEL")

pkg/config/config.go

@@ -26,9 +26,13 @@ func Load(configPath string) (*models.Config, error) {
 	if configPath != "" {
 		v.SetConfigFile(configPath)
 	} else {
-		// Look for config in standard locations
+		// Look for config in standard locations. We deliberately do NOT call
+		// SetConfigType: with a type set, viper also matches an extensionless
+		// file named "bagel" in the search path — so running `./bagel scan`
+		// from the binary's own directory makes viper try to parse the bagel
+		// binary as YAML ("control characters are not allowed"). Without a
+		// type, viper only matches bagel.<ext>.
 		v.SetConfigName("bagel")
-		v.SetConfigType("yaml")
 		v.AddConfigPath(GetConfigDir())
 		v.AddConfigPath(".")
 	}

pkg/config/config_test.go

@@ -4,10 +4,13 @@
 package config
 
 import (
+	"bytes"
 	"os"
 	"path/filepath"
 	"testing"
 
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -108,3 +111,46 @@ func TestLoad_ExplicitConfigFailsLoudly(t *testing.T) {
 	_, err := Load(missing)
 	require.Error(t, err)
 }
+
+// TestLoad_ExtensionlessBinaryNotMatched guards the regression where running
+// `./bagel scan` from the binary's own directory crashed with
+// "yaml: control characters are not allowed": with a config type set, viper
+// matches the extensionless `bagel` binary as a config file and tries to parse
+// it. Load must not even attempt to parse it.
+//
+// This asserts on the log output, not just the absence of an error: the
+// resilience switch in Load would swallow the parse failure and let the test
+// pass regardless. The only thing that proves the binary was never parsed is
+// that no "parsing config" failure was logged — which fails if SetConfigType
+// is restored.
+func TestLoad_ExtensionlessBinaryNotMatched(t *testing.T) {
+	logs := captureGlobalLog(t)
+
+	t.Setenv("HOME", t.TempDir())
+	dir := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "bagel"),
+		[]byte("\x7fELF\x02\x01\x01\x00\x00\x00"), 0o755)) // binary with control chars
+	t.Chdir(dir)
+
+	cfg, err := Load("")
+	require.NoError(t, err)
+	require.NotNil(t, cfg)
+	assert.True(t, cfg.Probes.Git.Enabled)
+	assert.NotEmpty(t, cfg.FileIndex.Patterns)
+
+	// The binary must never be fed to the YAML parser.
+	assert.NotContains(t, logs.String(), "parsing config",
+		"the bagel binary was matched and parsed as a config file; "+
+			"is SetConfigType set during auto-discovery?")
+}
+
+// captureGlobalLog redirects the package-global zerolog logger into a buffer
+// for the duration of the test and restores it afterward.
+func captureGlobalLog(t *testing.T) *bytes.Buffer {
+	t.Helper()
+	buf := &bytes.Buffer{}
+	prev := log.Logger
+	log.Logger = zerolog.New(buf)
+	t.Cleanup(func() { log.Logger = prev })
+	return buf
+}