fix: check for NaN value when floating the label in text field

Author: hperrin

MIGRATING.md

@@ -15,6 +15,7 @@ https://github.com/material-components/material-components-web/blob/master/CHANG
 - The "\*ComponentDev" types (like `MenuComponentDev`) are gone. You can now use the component as its type. Components that can take a `component` or `tag` prop (like `Button`) have required generic arguments that you can get around by using "InstanceType", like `let button: InstanceType<typeof Button>;`.
 - If you're using `classAdderBuilder`, you need to use `keyof SmuiElementMap` instead of `string` as its generic argument.
 - The `dispatch` function in `@smui/common` will now throw an error if either the `Event` object is not available or the `element` is not provided.
+- The `Input` component from the `@smui/textfield` now sets `value` to `Number.NaN` when the input is empty.
 
 ## Changes
 

packages/textfield/src/Input.svelte

@@ -104,7 +104,7 @@
 
   function toNumber(value: string) {
     if (value === '') {
-      return NaN;
+      return Number.NaN;
     }
     return +value;
   }

packages/textfield/src/Textfield.svelte

@@ -66,7 +66,10 @@
       {#if !noLabel && (label != null || $$slots.label)}
         <FloatingLabel
           bind:this={floatingLabel}
-          floatAbove={focused || (value != null && value !== '')}
+          floatAbove={focused ||
+            (value != null &&
+              value !== '' &&
+              (typeof value !== 'number' || !isNaN(value)))}
           {required}
           wrapped
           {...prefixFilter($$restProps, 'label$')}
@@ -83,7 +86,10 @@
         {#if !noLabel && (label != null || $$slots.label)}
           <FloatingLabel
             bind:this={floatingLabel}
-            floatAbove={focused || (value != null && value !== '')}
+            floatAbove={focused ||
+              (value != null &&
+                value !== '' &&
+                (typeof value !== 'number' || !isNaN(value)))}
             {required}
             wrapped
             {...prefixFilter($$restProps, 'label$')}