fix: validate config after PostLoad hooks

Re-run validator after PostLoad, return errors from RootDir, and add Config
alias for C(). Hooks receive *T instead of *Manager.

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

manager_test.go

@@ -0,0 +1,91 @@
+package config_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"gitea.auvem.com/go-toolkit/config"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type testSchema struct {
+	Name  string `mapstructure:"name" validate:"required"`
+	Port  int    `mapstructure:"port" validate:"required,min=1"`
+	Extra string `mapstructure:"extra"`
+}
+
+func writeConfig(t *testing.T, dir, content string) {
+	t.Helper()
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "app.yaml"), []byte(content), 0o644))
+}
+
+func TestLoadAndC(t *testing.T) {
+	dir := t.TempDir()
+	writeConfig(t, dir, "name: svc\nport: 8080\n")
+
+	m := config.NewManager[testSchema]("app", "yaml", dir)
+	require.NoError(t, m.Load())
+	assert.Equal(t, "svc", m.C().Name)
+	assert.Equal(t, 8080, m.Config().Port)
+}
+
+func TestPostLoadRevalidates(t *testing.T) {
+	dir := t.TempDir()
+	writeConfig(t, dir, "name: svc\nport: 8080\nextra: ok\n")
+
+	m := config.NewManager[testSchema]("app", "yaml", dir).WithOpts(&config.ManagerOpts[testSchema]{
+		PostLoad: func(cfg *testSchema) error {
+			cfg.Name = ""
+			return nil
+		},
+	})
+
+	err := m.Load()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "post-load")
+}
+
+func TestPostLoadSuccess(t *testing.T) {
+	dir := t.TempDir()
+	writeConfig(t, dir, "name: svc\nport: 8080\n")
+
+	m := config.NewManager[testSchema]("app", "yaml", dir).WithOpts(&config.ManagerOpts[testSchema]{
+		PostLoad: func(cfg *testSchema) error {
+			cfg.Extra = "derived"
+			return nil
+		},
+	})
+
+	require.NoError(t, m.Load())
+	assert.Equal(t, "derived", m.C().Extra)
+}
+
+func TestRootDir(t *testing.T) {
+	dir := t.TempDir()
+	marker := filepath.Join(dir, ".marker")
+	require.NoError(t, os.WriteFile(marker, []byte("x"), 0o644))
+
+	orig, err := os.Getwd()
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = os.Chdir(orig) })
+
+	sub := filepath.Join(dir, "sub")
+	require.NoError(t, os.Mkdir(sub, 0o755))
+	require.NoError(t, os.Chdir(sub))
+
+	got, err := config.RootDir(".marker", 1)
+	require.NoError(t, err)
+	absDir, err := filepath.EvalSymlinks(dir)
+	require.NoError(t, err)
+	gotEval, err := filepath.EvalSymlinks(got)
+	require.NoError(t, err)
+	assert.Equal(t, absDir, gotEval)
+}
+
+func TestMustRootDirPanics(t *testing.T) {
+	assert.Panics(t, func() {
+		config.MustRootDir("definitely-missing-marker-xyz", 0)
+	})
+}