expose svelte.walk (#2661)

site/content/docs/04-compile-time.md

@@ -280,6 +280,38 @@ const { code } = svelte.preprocess(source, [
 ```
 
 
+### `svelte.walk`
+
+```js
+walk(ast: Node, {
+	enter(node: Node, parent: Node)?: void,
+	leave(node: Node, parent: Node)?: void
+})
+```
+
+---
+
+The `walk` function provides a way to walk to abstract syntax trees generated by the parser, using the compiler's own built-in instance of [estree-walker](https://github.com/Rich-Harris/estree-walker).
+
+The walker takes an abstract syntax tree to walk and an object with two optional methods: `enter` and `leave`. For each node, `enter` is called (if present). Then, unless `this.skip()` is called during `enter`, each of the children are traversed, and then `leave` is called on the node.
+
+
+```js
+const svelte = require('svelte/compiler');
+svelte.walk(ast, {
+	enter(node, parent) {
+		do_something(node);
+		if (should_skip_children(node)) {
+			this.skip();
+		}
+	},
+	leave(node, parent) {
+		do_something_else(node);
+	}
+});
+```
+
+
 ### `svelte.VERSION`
 
 ---

src/index.ts

@@ -1,4 +1,5 @@
 export { default as compile } from './compile/index';
 export { default as preprocess } from './preprocess/index';
+export { walk } from 'estree-walker';
 
 export const VERSION = '__VERSION__';