Add label to OcSelect (#1570)

* Add label to OcSelect

* OcSelect: Add optionLabel prop which is passed as label to vue-select

* Move input-id into additional attributes computed prop

Co-authored-by: Dominik Schmidt <dev@dominik-schmidt.de>
Co-authored-by: Benedikt Kulmann <benedikt@kulmann.biz>

changelog/unreleased/change-ocselect-label

@@ -0,0 +1,9 @@
+Change: Label for OcSelect
+
+We've added a configurable `<label>` for OcSelect accessible via the `label` property.
+This shadows the `label` property of `vue-select`. Hence we introduced the `optionLabel`
+property on OcSelect which maps to the `label` property of `vue-select`.
+
+https://github.com/owncloud/owncloud-design-system/pull/1633
+https://github.com/owncloud/owncloud-design-system/pull/1570
+https://github.com/owncloud/owncloud-design-system/issues/1503

src/components/OcSelect.vue

@@ -1,13 +1,23 @@
 <template>
-  <vue-select ref="select" :value="model" class="oc-select" v-bind="$attrs" v-on="$listeners">
-    <template v-for="(index, name) in $scopedSlots" #[name]="data">
-      <slot :name="name" v-bind="data"></slot>
-    </template>
-    <div slot="no-options" v-translate>No options available.</div>
-  </vue-select>
+  <div>
+    <label :for="id" v-text="label" />
+    <vue-select
+      ref="select"
+      :value="model"
+      class="oc-select"
+      v-bind="additionalAttributes"
+      v-on="$listeners"
+    >
+      <template v-for="(index, name) in $scopedSlots" #[name]="data">
+        <slot :name="name" v-bind="data"></slot>
+      </template>
+      <div slot="no-options" v-translate>No options available.</div>
+    </vue-select>
+  </div>
 </template>
 
 <script>
+import uniqueId from "../utils/uniqueId"
 import VueSelect from "vue-select"
 import "vue-select/dist/vue-select.css"
 
@@ -27,16 +37,55 @@ export default {
   },
 
   props: {
+    /**
+     * The ID of the element.
+     */
+    id: {
+      type: String,
+      required: false,
+      default: () => uniqueId("oc-select-"),
+    },
+    /**
+     * The model of the select component. Provide it as value or bind it with v-model.
+     **/
     model: {
       type: [Array, String, Object],
       required: false,
       default: null,
     },
+    /**
+     * Label of the select component
+     * ATTENTION: this shadows the vue-select prop `label`. If you need access to that use `optionLabel`.
+     */
+    label: {
+      type: String,
+      default: null,
+    },
+    /**
+     * Key to use as label when option is an object
+     * NOTE: this maps to the vue-select prop `label`
+     */
+    optionLabel: {
+      type: String,
+      default: null,
+    },
+  },
+
+  computed: {
+    additionalAttributes() {
+      const additionalAttrs = {}
+      additionalAttrs["input-id"] = this.id
+      if (this.optionLabel) {
+        additionalAttrs["label"] = this.optionLabel
+      }
+      return { ...this.$attrs, ...additionalAttrs }
+    },
   },
 
   mounted() {
     this.setComboBoxAriaLabel()
   },
+
   methods: {
     setComboBoxAriaLabel() {
       const comboBoxElement = this.$refs.select.$el.querySelector("div:first-child")
@@ -98,7 +147,7 @@ For detailed documentation (props, slots, events, etc.), please visit https://vu
 ```js
 <template>
   <div class="oc-docs-width-medium">
-    <oc-select v-model="selected" :options="['Bannana', 'Orange', 'Pear']" />
+    <oc-select label="Custom label" v-model="selected" :options="['Bannana', 'Orange', 'Pear']" />
   </div>
 </template>
 <script>
@@ -146,14 +195,65 @@ export default {
 </script>
 ```
 
+### Use objects as options
+If we want to select from a list of option objects, we can use `option-label` to select the key of the object to use as label.
+
+```js
+<template>
+  <div class="oc-docs-width-medium">
+    <oc-select
+      label="Custom Label"
+      option-label="title"
+      :options="options"
+      v-model="selected"
+      class="oc-mb-m"
+    />
+  </div>
+</template>
+<script>
+const options = [
+  {
+    title: 'Apple',
+    desc: 'An apple is an edible fruit produced by an apple tree (Malus domestica)'
+  },
+  {
+    title: 'Bannana',
+    desc: 'Bannana is a genus of goblin spiders (family Oonopidae) native to Xishuangbanna prefecture, Yunnan Province, China, where it lives in the leaf-litter of tropical rainforest'
+  },
+  {
+    title: 'Orange',
+    desc: 'The orange is the fruit of various citrus species in the family Rutaceae'
+  },
+]
+
+export default {
+  data: () => ({
+    selected: options[1],
+    options
+  })
+}
+</script>
+```
+
+
+
+
 ### Using slots to display complex options
-Sometimes we need to display more complex options. This can include e.g. an option with a title and a description. To still display all those values exactly as we want to, we need to use scoped slot called `option`.
-We can then retrieve all the values that we want to display from the slots parametres. It is important to specify the `label` prop on the `oc-select` component which will specify which key should be used as the option label.
+Sometimes we need to display more complex options. This can include e.g. an option with a title and a description. To
+still display all those values exactly as we want to, we need to use scoped slots called `option` and `selected-option`.
+We can then retrieve all the values that we want to display from the slot parameters.
+It is important to specify the `option-label` prop on the `oc-select` to make filtering work.
 
 ```js
 <template>
   <div class="oc-docs-width-medium">
-    <oc-select v-model="selected" :options="options" label="title" class="oc-mb-m">
+    <oc-select
+      label="Custom Label"
+       option-label="title"
+      :options="options"
+      v-model="selected"
+      class="oc-mb-m"
+    >
       <template v-slot:option="{ title, desc }">
         <span class="option">
           <strong v-text="title" />