New Props API (#515)

* wip: update props api

* feat(#139, #309): enable new props api

* chore: migrate examples to new props API

* docs: update syntax guide for new props API

* chore: update examples to new props API

* chore: update docs to new Props API

* fix: hide __astroInternal from `Astro.props` consumers

* chore: remove scratchpad file

* chore: fix script error

* test: fix failing collection tests

* fix: set __astroInternal to `enumerable: false`

* chore: add changeset

* feat: warn users using old props api

1 files changed, 18 insertions, 5 deletions

diff --git a/docs/syntax.md b/docs/syntax.md
index 62b73104c..8476a2823 100644
--- a/docs/syntax.md
+++ b/docs/syntax.md
@@ -86,14 +86,27 @@ let name = 'world';
 </main>
 ```
 
-`.astro` components can also accept props when they are rendered. Public props can be marked using the `export` keyword.
-
-Local values are overwritten when props are passed, otherwise they are considered the default value.
+`.astro` components can also accept props when they are rendered. Public props are exposed on the `Astro.props` global.
 
 ```jsx
 ---
-export let greeting = 'Hello';
-export let name;
+const { greeting = 'Hello', name } = Astro.props;
+---
+
+<main>
+    <h1>{greeting} {name}!</h1>
+</main>
+```
+
+To define the props which your component accepts, you may export a TypeScript interface or type named `Props`.
+```tsx
+---
+export interface Props {
+  name: string;
+  greeting?: string;
+}
+
+const { greeting = 'Hello', name } = Astro.props;
 ---
 
 <main>