✨ [#2] Implement columns component schema type

src/formio/components/columns.ts

@@ -0,0 +1,59 @@
+import {AnyComponentSchema, LayoutComponentSchema} from '..';
+
+/**
+ * Configuration of a single column.
+ *
+ * Note that this deviates from Formio.js' own schema, as they are tightly coupled with
+ * Bootstrap properties/class names, which we deliberately avoid.
+ */
+export interface Column {
+  /**
+   * Size on non-mobile viewports.
+   *
+   * The size specifies the number of columns spanned in a 12-column grid. If no mobile
+   * size is specified, a 100% width is assumed.
+   */
+  size: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12;
+  /**
+   * Size on mobile viewports.
+   *
+   * The mobile size specifies the numbers of columns spanned in a 4-column grid.
+   *
+   * @todo Add backend migration to ensure this attribute is set everywhere.
+   */
+  sizeMobile: 1 | 2 | 3 | 4;
+  /**
+   * Nested components inside a single column.
+   */
+  components: AnyComponentSchema[];
+}
+
+/**
+ * The columns component schema.
+ *
+ * Columns are used to manage layout on desktop and mobile viewports by grouping nested
+ * components inside into columns.
+ *
+ * @group Form.io components
+ * @category Concrete types
+ */
+export interface ColumnsComponentSchema
+  extends Omit<
+    LayoutComponentSchema<never>,
+    | 'label'
+    | 'placeholder'
+    | 'multiple'
+    | 'defaultValue'
+    | 'conditional'
+    | 'errors'
+    | 'description'
+    | 'tooltip'
+    | 'hideLabel'
+    | 'disabled'
+    | 'validateOn'
+  > {
+  id: string;
+  key: string;
+  type: 'columns';
+  columns: Column[];
+}

src/formio/components/index.ts

@@ -21,3 +21,4 @@ export * from './radio';
 
 // Layout components
 export * from './content';
+export * from './columns';

src/formio/index.ts

@@ -1,6 +1,7 @@
 import {
   BsnComponentSchema,
   CheckboxComponentSchema,
+  ColumnsComponentSchema,
   ContentComponentSchema,
   CurrencyComponentSchema,
   DateComponentSchema,
@@ -67,7 +68,8 @@ export type AnyComponentSchema =
   | BsnComponentSchema
   | NpFamilyMembersComponentSchema
   // layout
-  | ContentComponentSchema;
+  | ContentComponentSchema
+  | ColumnsComponentSchema;
 
 /**
  * Convenience type alias for all supported concrete component schema types.

test-d/formio/components/columns.test-d.ts

@@ -0,0 +1,62 @@
+import {expectAssignable, expectNotAssignable} from 'tsd';
+
+import {Column, ColumnsComponentSchema} from '../../../lib';
+
+// Minimal schema
+expectAssignable<ColumnsComponentSchema>({
+  id: 'eqegfc',
+  type: 'columns',
+  key: 'columns',
+  columns: [],
+});
+
+// Full schema
+expectAssignable<ColumnsComponentSchema>({
+  id: 'eqegfc',
+  type: 'columns',
+  key: 'columns',
+  columns: [
+    {
+      size: 6,
+      sizeMobile: 4,
+      components: [
+        {
+          id: 'wien53il',
+          type: 'textfield',
+          key: 'nestedTextField',
+          label: 'Nested text field',
+        },
+      ],
+    },
+    {
+      size: 3,
+      sizeMobile: 4,
+      components: [
+        {
+          id: 'abcdefgh',
+          type: 'textfield',
+          key: 'nested2',
+          label: 'Second text field',
+        },
+      ],
+    },
+  ],
+});
+
+expectNotAssignable<Column>({
+  size: 0 as const,
+  sizeMobile: 4 as const,
+  components: [],
+});
+
+expectNotAssignable<Column>({
+  size: 13 as const,
+  sizeMobile: 4 as const,
+  components: [],
+});
+
+expectNotAssignable<Column>({
+  size: 3.14 as number,
+  sizeMobile: 4 as const,
+  components: [],
+});