feat: i18n better locale error handling

packages/core/dev-test/backends/proxy/config.yml

@@ -504,7 +504,7 @@ collections:
                 name: file
                 widget: file
   - name: i18n_playground
-    label: i18n Playground
+    label: i18n (Multiple Files)
     i18n: true
     folder: packages/core/dev-test/backends/proxy/_i18n_playground
     identifier_field: slug
@@ -524,6 +524,54 @@ collections:
         label: Date
         widget: datetime
         i18n: duplicate
+  - name: i18n_playground_multiple_folders
+    label: i18n (Multiple Folders)
+    i18n:
+      structure: multiple_folders
+      locales: [en, de, fr]
+      defaultLocale: en
+    folder: packages/core/dev-test/backends/proxy/_i18n_playground_multiple_folders
+    identifier_field: slug
+    create: true
+    fields:
+      # The slug field will be omitted from the translation.
+      - name: slug
+        label: Slug
+        widget: string
+      # same as 'i18n: translate'. Allows translation of the description field
+      - name: description
+        label: Description
+        widget: text
+        i18n: true
+      # The date field will be duplicated from the default locale.
+      - name: date
+        label: Date
+        widget: datetime
+        i18n: duplicate
+  - name: i18n_playground_single_file
+    label: i18n (Single File)
+    i18n:
+      structure: single_file
+      locales: [en, de, fr]
+      defaultLocale: en
+    folder: packages/core/dev-test/backends/proxy/_i18n_playground_multiple_folders
+    identifier_field: slug
+    create: true
+    fields:
+      # The slug field will be omitted from the translation.
+      - name: slug
+        label: Slug
+        widget: string
+      # same as 'i18n: translate'. Allows translation of the description field
+      - name: description
+        label: Description
+        widget: text
+        i18n: true
+      # The date field will be duplicated from the default locale.
+      - name: date
+        label: Date
+        widget: datetime
+        i18n: duplicate
   - name: pages
     label: Nested Pages
     label_singular: 'Page'

packages/core/src/__tests__/testConfig.ts

@@ -1794,6 +1794,62 @@ const testConfig: Config<RelationKitchenSinkPostField> = {
         },
       ],
     },
+    {
+      name: 'i18n_playground_multiple_folders',
+      label: 'i18n (Multiple Folders)',
+      i18n: {
+        structure: 'multiple_folders',
+        locales: ['en', 'de', 'fr'],
+        defaultLocale: 'en',
+      },
+      folder: 'packages/core/dev-test/backends/proxy/_i18n_playground_multiple_folders',
+      identifier_field: 'slug',
+      create: true,
+      fields: [
+        {
+          name: 'slug',
+          label: 'Slug',
+          widget: 'string',
+        },
+        {
+          name: 'description',
+          label: 'Description',
+          widget: 'text',
+          i18n: true,
+        },
+        {
+          name: 'date',
+          label: 'Date',
+          widget: 'datetime',
+          i18n: 'duplicate',
+        },
+      ],
+    },
+    {
+      name: 'i18n_playground_single_file',
+      label: 'i18n (Single File)',
+      i18n: {
+        structure: 'single_file',
+        locales: ['en', 'de', 'fr'],
+        defaultLocale: 'en',
+      },
+      folder: 'packages/core/dev-test/backends/proxy/_i18n_playground_single_file',
+      identifier_field: 'slug',
+      create: true,
+      fields: [
+        {
+          name: 'slug',
+          label: 'Slug',
+          widget: 'string',
+        },
+        {
+          name: 'description',
+          label: 'Description',
+          widget: 'text',
+          i18n: true,
+        },
+      ],
+    },
   ],
 };
 

packages/core/src/components/entry-editor/EditorInterface.css

@@ -14,19 +14,22 @@
 }
 
 & .CMS_Editor_i18n {
-  @apply flex
+  @apply hidden
     w-full
     overflow-y-auto
     h-main-mobile
     md:h-main;
+
+  &.CMS_Editor_i18n-active {
+    @apply flex;
+  }
 }
 
 & .CMS_Editor_mobile-i18n {
   @apply flex
     w-full
     overflow-y-auto
-    h-main-mobile
-    md:hidden;
+    h-main-mobile;
 }
 
 & .CMS_Editor_root {

packages/core/src/components/entry-editor/EditorInterface.tsx

@@ -4,6 +4,7 @@ import { ScrollSyncPane } from 'react-scroll-sync';
 import { EDITOR_SIZE_COMPACT } from '@staticcms/core/constants/views';
 import { summaryFormatter } from '@staticcms/core/lib/formatters';
 import useBreadcrumbs from '@staticcms/core/lib/hooks/useBreadcrumbs';
+import { useIsSmallScreen } from '@staticcms/core/lib/hooks/useMediaQuery';
 import { getI18nInfo, getPreviewEntry, hasI18n } from '@staticcms/core/lib/i18n';
 import classNames from '@staticcms/core/lib/util/classNames.util';
 import {
@@ -34,6 +35,7 @@ export const classes = generateClassNames('Editor', [
   'root',
   'default',
   'i18n',
+  'i18n-active',
   'mobile-i18n',
   'split-view',
   'mobile-preview',
@@ -120,10 +122,12 @@ const EditorInterface = ({
 }: TranslatedProps<EditorInterfaceProps>) => {
   const config = useAppSelector(selectConfig);
 
+  const isSmallScreen = useIsSmallScreen();
+
   const { locales, defaultLocale } = useMemo(() => getI18nInfo(collection), [collection]) ?? {};
   const translatedLocales = useMemo(
-    () => locales?.filter(locale => locale !== defaultLocale) ?? [],
-    [locales, defaultLocale],
+    () => (isSmallScreen ? locales : locales?.filter(locale => locale !== defaultLocale)) ?? [],
+    [isSmallScreen, locales, defaultLocale],
   );
 
   const [previewActive, setPreviewActive] = useState(
@@ -140,6 +144,10 @@ const EditorInterface = ({
     (i18nActive ? translatedLocales?.[0] : defaultLocale) ?? 'en',
   );
 
+  useEffect(() => {
+    setSelectedLocale((i18nActive ? translatedLocales?.[0] : defaultLocale) ?? 'en');
+  }, [defaultLocale, i18nActive, translatedLocales]);
+
   useEffect(() => {
     loadScroll();
   }, [loadScroll]);
@@ -293,24 +301,44 @@ const EditorInterface = ({
   );
 
   const editorLocale = useMemo(
-    () => (
-      <div key={selectedLocale} className={classes.i18n}>
-        <EditorControlPane
-          collection={collection}
-          entry={entry}
-          fields={fields}
-          fieldsErrors={fieldsErrors}
-          locale={selectedLocale}
-          onLocaleChange={handleLocaleChange}
-          submitted={submitted}
-          canChangeLocale
-          context="i18nSplit"
-          hideBorder
-          t={t}
-        />
-      </div>
-    ),
-    [collection, entry, fields, fieldsErrors, handleLocaleChange, selectedLocale, submitted, t],
+    () =>
+      locales
+        ?.filter(l => l !== defaultLocale)
+        .map(locale => (
+          <div
+            key={locale}
+            className={classNames(
+              classes.i18n,
+              selectedLocale === locale && classes['i18n-active'],
+            )}
+          >
+            <EditorControlPane
+              collection={collection}
+              entry={entry}
+              fields={fields}
+              fieldsErrors={fieldsErrors}
+              locale={locale}
+              onLocaleChange={handleLocaleChange}
+              submitted={submitted}
+              canChangeLocale
+              context="i18nSplit"
+              hideBorder
+              t={t}
+            />
+          </div>
+        )),
+    [
+      collection,
+      defaultLocale,
+      entry,
+      fields,
+      fieldsErrors,
+      handleLocaleChange,
+      locales,
+      selectedLocale,
+      submitted,
+      t,
+    ],
   );
 
   const previewEntry = useMemo(
@@ -320,24 +348,35 @@ const EditorInterface = ({
   );
 
   const mobileLocaleEditor = useMemo(
-    () => (
-      <div key={selectedLocale} className={classes['mobile-i18n']}>
-        <EditorControlPane
-          collection={collection}
-          entry={entry}
-          fields={fields}
-          fieldsErrors={fieldsErrors}
-          locale={selectedLocale}
-          onLocaleChange={handleLocaleChange}
-          allowDefaultLocale
-          submitted={submitted}
-          canChangeLocale
-          hideBorder
-          t={t}
-        />
-      </div>
-    ),
-    [collection, entry, fields, fieldsErrors, handleLocaleChange, selectedLocale, submitted, t],
+    () =>
+      isSmallScreen ? (
+        <div key={selectedLocale} className={classes['mobile-i18n']}>
+          <EditorControlPane
+            collection={collection}
+            entry={entry}
+            fields={fields}
+            fieldsErrors={fieldsErrors}
+            locale={selectedLocale}
+            onLocaleChange={handleLocaleChange}
+            allowDefaultLocale
+            submitted={submitted}
+            canChangeLocale
+            hideBorder
+            t={t}
+          />
+        </div>
+      ) : null,
+    [
+      collection,
+      entry,
+      fields,
+      fieldsErrors,
+      handleLocaleChange,
+      isSmallScreen,
+      selectedLocale,
+      submitted,
+      t,
+    ],
   );
 
   const editorWithPreview = (

packages/core/src/components/entry-editor/editor-control-pane/EditorControlPane.tsx

@@ -108,6 +108,7 @@ const EditorControlPane = ({
       {i18n?.locales && locale ? (
         <div className={classes.locale_dropdown_wrapper}>
           <LocaleDropdown
+            locale={locale}
             locales={i18n.locales}
             defaultLocale={i18n.defaultLocale}
             dropdownText={t('editor.editorControlPane.i18n.writingInLocale', {

packages/core/src/components/entry-editor/editor-control-pane/LocaleDropdown.css

@@ -1,4 +1,18 @@
 .CMS_LocaleDropdown_root {
+  &:not(.CMS_LocaleDropdown_no-edit) {
+    @apply flex
+      gap-2
+      items-center;
+  }
+}
+
+.CMS_LocaleDropdown_dropdown {
+}
+
+.CMS_LocaleDropdown_errors-icon {
+  @apply w-7
+    h-7
+    text-red-500;
 }
 
 .CMS_LocaleDropdown_no-edit {