[improvement] make props less magic (#3775)

src/picker/PickerColumn.js

@@ -35,8 +35,11 @@ export default createComponent({
     className: String,
     itemHeight: Number,
     defaultIndex: Number,
-    initialOptions: Array,
-    visibleItemCount: Number
+    visibleItemCount: Number,
+    initialOptions: {
+      type: Array,
+      default: () => []
+    }
   },
 
   data() {

src/picker/index.js

@@ -11,8 +11,14 @@ const [createComponent, bem, t] = createNamespace('picker');
 export default createComponent({
   props: {
     ...pickerProps,
-    columns: Array,
-    defaultIndex: Number,
+    defaultIndex: {
+      type: Number,
+      default: 0
+    },
+    columns: {
+      type: Array,
+      default: () => []
+    },
     toolbarPosition: {
       type: String,
       default: 'top'

src/picker/test/__snapshots__/index.spec.js.snap

@@ -2,7 +2,7 @@
 
 exports[`column watch default index 1`] = `
 <div class="van-picker-column">
-  <ul class="van-picker-column__wrapper" style="transform: translate3d(0, -75px, 0); transition-duration: 0ms; transition-property: none; line-height: 50px;">
+  <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 100px, 0); transition-duration: 0ms; transition-property: none; line-height: 50px;">
     <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled" style="height: 50px;">1</li>
     <li class="van-ellipsis van-picker-column__item" style="height: 50px;">1990</li>
     <li class="van-ellipsis van-picker-column__item" style="height: 50px;">1991</li>
@@ -16,7 +16,7 @@ exports[`column watch default index 1`] = `
 
 exports[`column watch default index 2`] = `
 <div class="van-picker-column">
-  <ul class="van-picker-column__wrapper" style="transform: translate3d(0, -125px, 0); transition-duration: 0ms; transition-property: none; line-height: 50px;">
+  <ul class="van-picker-column__wrapper" style="transform: translate3d(0, 0px, 0); transition-duration: 0ms; transition-property: none; line-height: 50px;">
     <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled" style="height: 50px;">1</li>
     <li class="van-ellipsis van-picker-column__item" style="height: 50px;">1990</li>
     <li class="van-ellipsis van-picker-column__item" style="height: 50px;">1991</li>

src/picker/test/index.spec.js

@@ -114,7 +114,8 @@ test('column watch default index', async () => {
     propsData: {
       initialOptions: [disabled, ...simpleColumn],
       valueKey: 'text',
-      itemHeight: 50
+      itemHeight: 50,
+      visibleItemCount: 5
     }
   });