fix: harden module lifecycle and debug log setup

Export CurrentDialect(), return setup errors when debug logger is not
registered, and guard DestName logging when the module is uninitialized.

Co-authored-by: Cursor <cursoragent@cursor.com>

dest.go

@@ -20,14 +20,14 @@ func DestName(destTypeStruct any, path ...string) string {
 
 	for i, p := range path {
 		if v.Kind() != reflect.Struct {
-			dbxshared.DBModule.Logger().Error("DestName: path parent is not a struct", "path", destIdent+"."+strings.Join(path[:i+1], "."))
+			destNameLogError("DestName: path parent is not a struct", destIdent+"."+strings.Join(path[:i+1], "."))
 			return ""
 		}
 
 		v = v.FieldByName(p)
 
 		if !v.IsValid() {
-			dbxshared.DBModule.Logger().Error("DestName: field does not exist", "path", destIdent+"."+strings.Join(path[:i+1], "."))
+			destNameLogError("DestName: field does not exist", destIdent+"."+strings.Join(path[:i+1], "."))
 			return ""
 		}
 
@@ -36,3 +36,10 @@ func DestName(destTypeStruct any, path ...string) string {
 
 	return destIdent
 }
+
+func destNameLogError(msg, path string) {
+	if dbxshared.DBModule == nil {
+		return
+	}
+	dbxshared.DBModule.Logger().Error(msg, "path", path)
+}

internal/dbxshared/logger.go

@@ -1,5 +1,7 @@
 package dbxshared
 
+import "fmt"
+
 type Logger interface {
 	InitLogger()
 }
@@ -20,11 +22,17 @@ func RegisterLogger(dialect dialectString, logger Logger) {
 }
 
 // InitLogger initializes the logger for a specific dialect.
-func InitLogger(dialect dialectString) {
+func InitLogger(dialect dialectString) error {
 	dialectStr := dialect.String()
 	logger, exists := loggerRegistry[dialectStr]
 	if !exists {
-		panic("No logger registered for dialect: " + dialectStr)
+		return fmt.Errorf("no logger registered for dialect %q: blank-import dbxm (MySQL) or dbxp (Postgres)", dialectStr)
 	}
 	logger.InitLogger()
+	return nil
+}
+
+// ResetLoggerRegistry clears registered loggers. It is intended for tests only.
+func ResetLoggerRegistry() {
+	loggerRegistry = make(map[string]Logger)
 }

internal/dbxshared/logger_test.go

@@ -0,0 +1,32 @@
+package dbxshared
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type testDialect string
+
+func (d testDialect) String() string { return string(d) }
+
+type stubLogger struct{}
+
+func (stubLogger) InitLogger() {}
+
+func TestInitLogger_UnregisteredDialect(t *testing.T) {
+	ResetLoggerRegistry()
+	t.Cleanup(ResetLoggerRegistry)
+
+	err := InitLogger(testDialect("mysql"))
+	assert.ErrorContains(t, err, "blank-import dbxm")
+}
+
+func TestInitLogger_RegisteredDialect(t *testing.T) {
+	ResetLoggerRegistry()
+	t.Cleanup(ResetLoggerRegistry)
+
+	RegisterLogger(testDialect("mysql"), stubLogger{})
+	err := InitLogger(testDialect("mysql"))
+	assert.NoError(t, err)
+}

module.go

@@ -45,6 +45,11 @@ var (
 	state = dbState{}
 )
 
+// CurrentDialect returns the SQL dialect configured by [ModuleDB].
+func CurrentDialect() Dialect {
+	return state.dialect
+}
+
 // SQLO returns the current SQL database handle.
 func SQLO() *sql.DB {
 	dbxshared.DBModule.RequireLoaded("dbx.SQLO requires database module")
@@ -118,7 +123,10 @@ func setupDB(m *app.Module) error {
 	)
 
 	if state.debugLog {
-		dbxshared.InitLogger(state.dialect)
+		if err := dbxshared.InitLogger(state.dialect); err != nil {
+			m.Logger().Error("Couldn't initialize Jet query debug logger", "err", err)
+			return err
+		}
 	}
 
 	return nil

module_test.go

@@ -0,0 +1,45 @@
+package dbx
+
+import (
+	"testing"
+
+	"gitea.auvem.com/go-toolkit/dbx/internal/dbxshared"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDestName_MissingFieldWithoutModule(t *testing.T) {
+	type Foo struct {
+		Bar int
+	}
+
+	name := DestName(Foo{}, "Missing")
+	assert.Empty(t, name)
+}
+
+func TestDestName_ValidPath(t *testing.T) {
+	type Inner struct {
+		Value string
+	}
+	type Foo struct {
+		Inner Inner
+	}
+
+	name := DestName(Foo{}, "Inner", "Value")
+	assert.Equal(t, "Foo.Inner.Value", name)
+}
+
+func TestDialect_AfterModuleDB(t *testing.T) {
+	if dbxshared.DBModule != nil {
+		t.Skip("database module already initialized")
+	}
+
+	_ = ModuleDB(DialectPostgres, &DBConfig{
+		User:     "user",
+		Password: "pass",
+		URI:      "localhost:5432",
+		Name:     "test",
+		MaxConn:  1,
+	}, false)
+
+	assert.Equal(t, DialectPostgres, CurrentDialect())
+}