fix(Select): Only dispatch populated event when appropriate

This fixes a problem where, when the Select's value is changed (by the
user), the `change` and `populated` events are both dispatched, even if
the list of options is unchanged.

Those subsequent dispatches of the `populated` event make it too easy
for consumers of this component to accidentally set the value of the
Select back to what it was an instant before, effectively preventing
the user's choice from "sticking" sometimes.

Author: forevermatt

components/mdc/Select/Select.svelte

@@ -21,12 +21,17 @@ const selectedTextID = generateRandomID('select-selected-text-')
 
 let element = {}
 let mdcSelect = {}
+let previousOptionsIDsCSV = ''
 
 $: selectedIndex = options.findIndex((option) => option.id === selectedID)
 $: dispatch('change', options[selectedIndex] || {})
 $: mdcSelect.disabled = disabled
 $: if (options && mdcSelect.layoutOptions) mdcSelect.layoutOptions()
 
+const getIDsCSV = (options) => options.map(option => option.id).join(',')
+
+const optionsHaveChanged = (options) => previousOptionsIDsCSV !== getIDsCSV(options)
+
 const recordSelectedID = (event) => (selectedID = event.detail.value)
 
 const isOptionSelected = (option) => option.id === selectedID
@@ -43,10 +48,11 @@ afterUpdate(() => {
   // This makes sure the index is updated AFTER the select list contains the full list of options.
   mdcSelect.selectedIndex = selectedIndex
 
-  // If options have been provided, give the current processes time to finish
+  // If options have been provided or changed, give the current processes time to finish
   // what they're doing, then indicate that this Select is now populated with
   // options. At this point, it's safe for the selectedID to be initialized.
-  if (options.length > 0) {
+  if (options.length > 0 && optionsHaveChanged(options)) {
+    previousOptionsIDsCSV = getIDsCSV(options)
     setTimeout(() => {
       dispatch('populated')
     })