fix(checkbox-group): throw if name does not contain []

packages/checkbox-group/README.md

@@ -35,3 +35,23 @@ import '@lion/checkbox-group/lion-checkbox-group.js';
   <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
 </lion-checkbox-group>
 ```
+
+### Model value
+
+The `modelValue` of a `lion-checkbox-group` is an array containing the `choiceValues` of the `lion-checkbox` elements that have been checked.
+
+Given the scientists example above, say that we were to select the first and last options (Archimedes & Marie Curie).
+
+Then the `modelValue` of the `lion-checkbox-group` will look as follows:
+
+```js
+const groupElement = [parent].querySelector('lion-checkbox-group');
+groupElement.modelValue;
+  => ["Archimedes", "Marie Curie"];
+```
+
+### The `name` attribute
+
+The `name` attribute of a `lion-checkbox-group` automatically gets assigned to its `lion-checkbox` children. You can also specify names for the `lion-checkbox` elements, but if this name is different from the name assigned to `lion-checkbox-group`, then an exception will be thrown.
+
+Our recommendation would be to set the `name` attribute only on the `lion-checkbox-group` and not on the `lion-checkbox` elements.

packages/checkbox-group/src/LionCheckboxGroup.js

@@ -6,4 +6,11 @@ export class LionCheckboxGroup extends ChoiceGroupMixin(LionFieldset) {
     super();
     this.multipleChoice = true;
   }
+
+  updated(changedProperties) {
+    super.updated(changedProperties);
+    if (changedProperties.has('name') && !String(this.name).match(/\[\]$/)) {
+      throw new Error('Names should end in "[]".');
+    }
+  }
 }

packages/checkbox-group/test/lion-checkbox-group.test.js

@@ -53,4 +53,21 @@ describe('<lion-checkbox-group>', () => {
     `);
     await expect(el).to.be.accessible();
   });
+
+  it("should throw exception if name doesn't end in []", async () => {
+    const el = await fixture(
+      html`
+        <lion-checkbox-group name="woof[]"></lion-checkbox-group>
+      `,
+    );
+    el.name = 'woof';
+    let err;
+    try {
+      await el.updateComplete;
+    } catch (e) {
+      err = e;
+    }
+    expect(err).to.be.an.instanceof(Error);
+    expect(err.message).to.equal('Names should end in "[]".');
+  });
 });

packages/form-system/stories/15-features-overview.stories.mdx

@@ -1,5 +1,4 @@
-import { Story, Preview, Meta, html } from '@open-wc/demoing-storybook';
-import '@lion/checkbox-group/lion-checkbox-group.js';
+import { Story, Meta, html } from '@open-wc/demoing-storybook';
 import '@lion/checkbox/lion-checkbox.js';
 import '@lion/fieldset/lion-fieldset.js';
 import '@lion/form/lion-form.js';
@@ -59,7 +58,7 @@ For usage and installation please see the appropriate packages.
           <lion-input-email name="email" label="Email"></lion-input-email>
           <lion-checkbox-group
             label="What do you like?"
-            name="checkers"
+            name="checkers[]"
             .validators="${[new Required()]}"
           >
             <lion-checkbox .choiceValue=${'foo'} label="I like foo"></lion-checkbox>

packages/radio-group/README.md

@@ -35,3 +35,23 @@ import '@lion/radio-group/lion-radio-group.js';
 
 - Make sure that to use a name attribute as it is necessary for the [lion-form](../form)'s serialization result.
 - If you have many options for a user to pick from, consider using [`lion-select`](../select) instead
+
+### Model value
+
+The `modelValue` of a `lion-radio-group` is string equal to the `choiceValue` of the `lion-radio` element that has been checked.
+
+Given the dinosaur example above, say that we were to select the last option (diplodocus).
+
+Then the `modelValue` of the `lion-radio-group` will look as follows:
+
+```js
+const groupElement = [parent].querySelector('lion-radio-group');
+groupElement.modelValue;
+  => "diplodocus";
+```
+
+### The `name` attribute
+
+The `name` attribute of a `lion-radio-group` automatically gets assigned to its `lion-radio` children. You can also specify names for the `lion-radio` elements, but if this name is different from the name assigned to `lion-radio-group`, then an exception will be thrown.
+
+Our recommendation would be to set the `name` attribute only on the `lion-radio-group` and not on the `lion-checkbox` elements.