fix(cabana): dereference nullable pointer scalars in ML host hydration

- hostScalarString walks pointers via reflect; nil at any depth is ""
- string kinds return raw text, byte slices decode, other kinds format the dereferenced value
- Postgres round-trip regression for an mltext field on a *string column

modules/cabana/ml_nullable_test.go

@@ -0,0 +1,182 @@
+package cabana
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"git.golem15.com/golem15/summercms/modules/pact"
+	"gorm.io/gorm"
+)
+
+const mlNullableFields = `fields:
+    title:
+        label: Title
+        type: mltext
+        required: true
+    description:
+        label: Description
+        type: mltext
+`
+
+type mlNullablePost struct {
+	ID          uint    `gorm:"column:id;primaryKey"`
+	Title       string  `gorm:"column:title"`
+	Description *string `gorm:"column:description"`
+}
+
+func (mlNullablePost) TableName() string        { return "cabana_ml_nullable_posts" }
+func (mlNullablePost) Fillable() []string       { return []string{"title", "description"} }
+func (mlNullablePost) Rules() map[string]string { return map[string]string{"title": "required"} }
+
+type mlNullableController struct{}
+
+func (mlNullableController) ID() string        { return "acme.demo.posts" }
+func (mlNullableController) ModelName() string { return "Post" }
+func (mlNullableController) ConfigDir() string { return "controllers/posts" }
+func (mlNullableController) NewRecord() any    { return &mlNullablePost{} }
+
+func (mlNullableController) FormExtendQuery(ctx context.Context, q *gorm.DB) *gorm.DB {
+	return q
+}
+
+var (
+	_ pact.AdminController   = mlNullableController{}
+	_ pact.AdminRecordSource = mlNullableController{}
+	_ pact.FormExtendQuery   = mlNullableController{}
+)
+
+func mlNullableFS() fstest.MapFS {
+	fsys := mlFS()
+	fsys["models/post/fields.yaml"] = &fstest.MapFile{Data: []byte(mlNullableFields)}
+	return fsys
+}
+
+func mlNullableCompiled(t *testing.T) *CompiledController {
+	t.Helper()
+	reg, err := compileRegistry([]controllerRef{{
+		plugin: formPlugin{fsys: mlNullableFS()},
+		ctl:    mlNullableController{},
+	}})
+	if err != nil {
+		t.Fatalf("registry: %v", err)
+	}
+	cc, ok := reg.Get("acme.demo.posts")
+	if !ok || cc.Form == nil {
+		t.Fatalf("compiled controller missing form: %+v", cc)
+	}
+	return cc
+}
+
+// assertNoPointerLeak fails when a hydrated value carries the text of a Go
+// pointer instead of the value it points at.
+func assertNoPointerLeak(t *testing.T, where, got string) {
+	t.Helper()
+	if strings.Contains(got, "<nil>") || strings.HasPrefix(got, "0x") {
+		t.Fatalf("%s = %q, leaked a pointer instead of its value", where, got)
+	}
+}
+
+// mlLocaleMap asserts data[field] is a hydrated locale map with no pointer
+// leak in any locale and returns it.
+func mlLocaleMap(t *testing.T, where string, data map[string]any, field string) map[string]string {
+	t.Helper()
+	got, ok := data[field].(map[string]string)
+	if !ok {
+		t.Fatalf("%s %s = %#v, want hydrated locale map", where, field, data[field])
+	}
+	for code, text := range got {
+		assertNoPointerLeak(t, where+" "+field+"."+code, text)
+	}
+	return got
+}
+
+func TestMLNullablePointerHost(t *testing.T) {
+	_, db := newListService(t)
+	if err := db.Migrator().DropTable(&mlNullablePost{}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.AutoMigrate(&mlNullablePost{}); err != nil {
+		t.Fatal(err)
+	}
+	writer := &recordingWriter{defaultLocale: "en", enabled: []string{"en", "pl"}}
+	svc := CRUDService{DB: db, writer: writer}
+	cc := mlNullableCompiled(t)
+	ctx := context.Background()
+
+	row := mlNullablePost{Title: "Hello"}
+	if err := db.Create(&row).Error; err != nil {
+		t.Fatal(err)
+	}
+	title := map[string]any{"en": "Hello", "pl": "Witaj"}
+
+	t.Run("nil pointer host hydrates to empty strings", func(t *testing.T) {
+		shown, err := svc.ShowRecord(ctx, cc, row.ID)
+		if err != nil {
+			t.Fatalf("show: %v", err)
+		}
+		got := mlLocaleMap(t, "show", shown.Data, "description")
+		if got["en"] != "" || got["pl"] != "" || len(got) != 2 {
+			t.Fatalf("nil description = %#v, want en and pl empty", got)
+		}
+	})
+
+	t.Run("cleared value round-trips as empty string", func(t *testing.T) {
+		saved, err := svc.UpdateRecord(ctx, cc, row.ID, RecordInput{Body: map[string]any{
+			"title":       title,
+			"description": map[string]any{"en": "", "pl": ""},
+		}})
+		if err != nil {
+			t.Fatalf("update: %v", err)
+		}
+		if got := mlLocaleMap(t, "save", saved.Data, "description"); got["en"] != "" {
+			t.Fatalf("saved description = %#v, want en empty", got)
+		}
+		shown, err := svc.ShowRecord(ctx, cc, row.ID)
+		if err != nil {
+			t.Fatalf("show: %v", err)
+		}
+		if got := mlLocaleMap(t, "show", shown.Data, "description"); got["en"] != "" || got["pl"] != "" {
+			t.Fatalf("shown description = %#v, want en and pl empty", got)
+		}
+		var stored mlNullablePost
+		if err := db.First(&stored, row.ID).Error; err != nil {
+			t.Fatal(err)
+		}
+		if stored.Description == nil || *stored.Description != "" {
+			t.Fatalf("stored description = %v, want pointer to empty string", stored.Description)
+		}
+	})
+
+	t.Run("filled value stores host text and writes translation", func(t *testing.T) {
+		saved, err := svc.UpdateRecord(ctx, cc, row.ID, RecordInput{Body: map[string]any{
+			"title":       title,
+			"description": map[string]any{"en": "Opis kategorii", "pl": "Opis"},
+		}})
+		if err != nil {
+			t.Fatalf("update: %v", err)
+		}
+		if got := mlLocaleMap(t, "save", saved.Data, "description"); got["en"] != "Opis kategorii" {
+			t.Fatalf("saved description = %#v", got)
+		}
+		shown, err := svc.ShowRecord(ctx, cc, row.ID)
+		if err != nil {
+			t.Fatalf("show: %v", err)
+		}
+		got := mlLocaleMap(t, "show", shown.Data, "description")
+		if got["en"] != "Opis kategorii" || got["pl"] != "Opis" {
+			t.Fatalf("shown description = %#v", got)
+		}
+		var stored mlNullablePost
+		if err := db.First(&stored, row.ID).Error; err != nil {
+			t.Fatal(err)
+		}
+		if stored.Description == nil || *stored.Description != "Opis kategorii" {
+			t.Fatalf("stored description = %v, want Opis kategorii", stored.Description)
+		}
+		if writer.attrs["pl"]["description"] != "Opis" {
+			t.Fatalf("Polish attributes = %#v", writer.attrs)
+		}
+	})
+}