feat(17-01): repeater field type and the dependent dropdown save recheck

- cabana: type repeater with nested form.fields (text, textarea, number,
  checkbox, switch, dropdown, richeditor), prompt, minItems, maxItems,
  titleFrom; groups, style, nested repeaters and other types fail boot
- rows decoded before projection: only nested keys, coerced scalars,
  per-row required (field.index.nested), row bounds; ProjectWritableFields
  exempts repeater lists only, nestedValue unchanged
- nested richeditor values sanitized with notices under the row path
- dependent dropdowns rechecked on save, top level and per row; null when
  the sibling takes no choice, 422 form.dependent_invalid otherwise
- dependent-options accepts repeater.field; schema carries RepeaterForm
- backend lang repeater.max_items, repeater.min_items,
  form.dependent_invalid; TestCompanionsRepeaterSmoke; docs

modules/cabana/form_schema.go

@@ -27,7 +27,7 @@ var (
 		"widget": {}, "partial": {}, "fileupload": {}, "datepicker": {},
 		"password": {}, "permissioneditor": {},
 		"markdown": {}, "mltext": {}, "mltextarea": {}, "mlmarkdown": {},
-		"richeditor": {},
+		"richeditor": {}, "repeater": {},
 	}
 	formSpans = map[string]struct{}{
 		"left": {}, "right": {}, "full": {}, "auto": {}, "row": {},
@@ -46,6 +46,8 @@ var (
 		"format": {}, "minDate": {}, "maxDate": {}, "yearRange": {},
 		"firstDay": {}, "twelveHour": {}, "ignoreTimezone": {},
 		"preset": {}, "dependsOn": {},
+		"form": {}, "maxItems": {}, "minItems": {}, "titleFrom": {},
+		"groups": {}, "style": {},
 	}
 	// widgetKeys are valid only on `type: widget` (D-06).
 	widgetKeys = []string{"widget", "action", "fill"}
@@ -264,26 +266,10 @@ func (s *FormSchema) Localize(ctx context.Context, tr *phrasebook.Translator, pr
 	ctx = towel.WithLocale(ctx, locale)
 	fields := make([]FormField, len(s.Fields))
 	for i, src := range s.Fields {
-		field := src
-		field.Label = translateKey(ctx, tr, src.Label)
-		field.Comment = translateKey(ctx, tr, src.Comment)
-		field.Tab = translateKey(ctx, tr, src.Tab)
-		field.EmptyOption = translateKey(ctx, tr, src.EmptyOption)
-		field.ActionLabel = translateKey(ctx, tr, src.ActionLabel)
-		field.Prompt = translateKey(ctx, tr, src.Prompt)
-		field.Fill = append([]string(nil), src.Fill...)
-		if src.Preset != nil {
-			preset := *src.Preset
-			field.Preset = &preset
-		}
-		field.FileTypes = append([]string(nil), src.FileTypes...)
-		field.MimeTypes = append([]string(nil), src.MimeTypes...)
-		field.YearRange = append([]int(nil), src.YearRange...)
-		options, err := localizeOptions(ctx, tr, src, provider)
+		field, err := localizeField(ctx, tr, src, provider, src.Name)
 		if err != nil {
 			return nil, err
 		}
-		field.Options = options
 		fields[i] = field
 	}
 	if fields == nil {
@@ -329,6 +315,45 @@ func (s *FormSchema) CanonicalJSON() ([]byte, error) {
 	return json.Marshal(out)
 }
 
+// localizeField copies one field and resolves its display strings and
+// options for a request. path is the name the dropdown provider is asked
+// with: the field name, or repeater.nested for a field of a repeater row.
+func localizeField(ctx context.Context, tr *phrasebook.Translator, src FormField, provider pact.DropdownOptionsProvider, path string) (FormField, error) {
+	field := src
+	field.Label = translateKey(ctx, tr, src.Label)
+	field.Comment = translateKey(ctx, tr, src.Comment)
+	field.Tab = translateKey(ctx, tr, src.Tab)
+	field.EmptyOption = translateKey(ctx, tr, src.EmptyOption)
+	field.ActionLabel = translateKey(ctx, tr, src.ActionLabel)
+	field.Prompt = translateKey(ctx, tr, src.Prompt)
+	field.Fill = append([]string(nil), src.Fill...)
+	if src.Preset != nil {
+		preset := *src.Preset
+		field.Preset = &preset
+	}
+	field.FileTypes = append([]string(nil), src.FileTypes...)
+	field.MimeTypes = append([]string(nil), src.MimeTypes...)
+	field.YearRange = append([]int(nil), src.YearRange...)
+	named := src
+	named.Name = path
+	options, err := localizeOptions(ctx, tr, named, provider)
+	if err != nil {
+		return FormField{}, err
+	}
+	field.Options = options
+	if src.Form != nil {
+		nested := make([]FormField, len(src.Form.Fields))
+		for i, inner := range src.Form.Fields {
+			nested[i], err = localizeField(ctx, tr, inner, provider, src.Name+"."+inner.Name)
+			if err != nil {
+				return FormField{}, err
+			}
+		}
+		field.Form = &RepeaterForm{Fields: nested}
+	}
+	return field, nil
+}
+
 func requireDropdownProvider(ctl pact.AdminController, fields []FormField) error {
 	var method string
 	for _, field := range fields {
@@ -336,6 +361,16 @@ func requireDropdownProvider(ctl pact.AdminController, fields []FormField) error
 			method = field.optionsMethod
 			break
 		}
+		if field.Form != nil {
+			for _, inner := range field.Form.Fields {
+				if inner.optionsMethod != "" && method == "" {
+					method = inner.optionsMethod
+				}
+			}
+			if method != "" {
+				break
+			}
+		}
 	}
 	if method == "" || dropdownProvider(ctl) != nil {
 		return nil
@@ -602,6 +637,9 @@ func compileFieldNode(name string, node ast.Node, types *fieldTypeRegistry) (For
 	if err := compileDependsOn(typ, values, &field); err != nil {
 		return FormField{}, err
 	}
+	if err := compileRepeater(name, typ, values, &field); err != nil {
+		return FormField{}, err
+	}
 	if node, ok := values["required"]; ok {
 		field.Required, err = nodeBool(node)
 		if err != nil {