fix: handle missing config file without panicking

pgmgr/config.go

@@ -19,6 +19,7 @@ type argumentContext interface {
 	Int(string) int
 	StringSlice(string) []string
 	Bool(string) bool
+	IsSet(string) bool
 }
 
 // Config stores the options used by pgmgr.
@@ -55,7 +56,7 @@ func LoadConfig(config *Config, ctx argumentContext) error {
 	// load configuration from file first; then override with
 	// flags or env vars if they're present.
 	configFile := ctx.String("config-file")
-	if err := config.populateFromFile(configFile); err != nil {
+	if err := config.populateFromFile(configFile, ctx.IsSet("config-file")); err != nil {
 		return err
 	}
 
@@ -77,12 +78,15 @@ func LoadConfig(config *Config, ctx argumentContext) error {
 	return config.validate()
 }
 
-func (config *Config) populateFromFile(configFile string) error {
+func (config *Config) populateFromFile(configFile string, explicit bool) error {
 	if configFile == "" {
 		return nil
 	}
 	contents, err := os.ReadFile(configFile)
 	if err != nil {
+		if !explicit && errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
 		return err
 	}
 	if err := json.Unmarshal(contents, &config); err != nil {

pgmgr/config_test.go

@@ -3,6 +3,7 @@ package pgmgr
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"testing"
 )
 
@@ -12,6 +13,7 @@ type TestContext struct {
 	IntVals         map[string]int
 	StringSliceVals map[string][]string
 	BoolVals        map[string]bool
+	IsSetVals       map[string]bool
 }
 
 func (t *TestContext) String(key string) string {
@@ -26,6 +28,9 @@ func (t *TestContext) StringSlice(key string) []string {
 func (t *TestContext) Bool(key string) bool {
 	return t.BoolVals[key]
 }
+func (t *TestContext) IsSet(key string) bool {
+	return t.IsSetVals[key]
+}
 
 func TestDefaults(t *testing.T) {
 	c := &Config{}
@@ -193,3 +198,56 @@ func TestQuotedMigrationTable(t *testing.T) {
 		t.Fatal(`Schema-qualified migration table should be "abc"."def", got`, c.quotedMigrationTable())
 	}
 }
+
+func TestMissingDefaultConfigFile(t *testing.T) {
+	// Simulate production: no .pgmgr.json in the working dir,
+	// config-file flag was NOT explicitly set by the user.
+	c := &Config{}
+	ctx := &TestContext{
+		StringVals: map[string]string{
+			"config-file": filepath.Join(t.TempDir(), ".pgmgr.json"),
+		},
+		IsSetVals: map[string]bool{
+			"config-file": false, // key distinction: user did not pass --config-file
+		},
+	}
+
+	if err := LoadConfig(c, ctx); err != nil {
+		t.Fatal("LoadConfig should succeed when default config file is missing, but got:", err)
+	}
+}
+
+func TestExplicitMissingConfigFileErrors(t *testing.T) {
+	c := &Config{}
+	ctx := &TestContext{
+		StringVals: map[string]string{
+			"config-file": filepath.Join(t.TempDir(), "explicit-missing.json"),
+		},
+		IsSetVals: map[string]bool{
+			"config-file": true, // user explicitly passed --config-file
+		},
+	}
+
+	if err := LoadConfig(c, ctx); err == nil {
+		t.Fatal("LoadConfig should fail when explicitly-given config file is missing")
+	}
+}
+
+func TestExplicitEnvVarMissingConfigFileErrors(t *testing.T) {
+	// When PGMGR_CONFIG_FILE env var is set to a path that doesn't exist,
+	// LoadConfig should fail — the user explicitly configured a path.
+	missingPath := filepath.Join(t.TempDir(), "from-env-var.json")
+	c := &Config{}
+	ctx := &TestContext{
+		StringVals: map[string]string{
+			"config-file": missingPath,
+		},
+		IsSetVals: map[string]bool{
+			"config-file": true, // urfave/cli sets IsSet=true when EnvVar is present
+		},
+	}
+
+	if err := LoadConfig(c, ctx); err == nil {
+		t.Fatal("LoadConfig should fail when config file path from env var does not exist")
+	}
+}