Support {#key} block

package.json

@@ -36,7 +36,7 @@
         "rollup-plugin-commonjs": "9.2.0",
         "rollup-plugin-node-resolve": "4.0.0",
         "rollup-plugin-typescript": "1.0.0",
-        "svelte": "^3.20.0",
+        "svelte": "^3.28.0",
         "ts-node": "^7.0.1",
         "tslib": "^1.9.3",
         "typescript": "3.2.4"

src/print/index.ts

@@ -377,6 +377,18 @@ export function print(path: FastPath, options: ParserOptions, print: PrintFn): D
 
             return group(concat(block));
         }
+        case 'KeyBlock': {
+            const def: Doc[] = [
+                '{#key ',
+                printJS(path, print, 'expression'),
+                '}',
+                printIndentedWithNewlines(path, print),
+            ];
+
+            def.push('{/key}');
+
+            return concat([group(concat(def)), breakParent]);
+        }
         case 'ThenBlock':
         case 'PendingBlock':
         case 'CatchBlock':
@@ -439,7 +451,7 @@ export function print(path: FastPath, options: ParserOptions, print: PrintFn): D
         case 'Comment': {
             /**
              * If there is no sibling node that starts right after us but the parent indicates
-             * that there used to be, that means that node was actually an embedded `<style>` 
+             * that there used to be, that means that node was actually an embedded `<style>`
              * or `<script>` node that was cut out.
              * If so, the comment does not refer to the next line we will see.
              * The `embed` function handles printing the comment in the right place.
@@ -545,7 +557,7 @@ function printChildren(path: FastPath, print: PrintFn): Doc[] {
      */
     function outputChildDoc(childDoc?: Doc, fromNode?: Node) {
         if (!isPreformat) {
-            if ((!childDoc || !fromNode || canBreakBefore(fromNode))) {
+            if (!childDoc || !fromNode || canBreakBefore(fromNode)) {
                 linebreakPossible();
 
                 const lastChild = childDocs[childDocs.length - 1];

src/print/nodes.ts

@@ -76,6 +76,12 @@ export interface AwaitBlockNode extends BaseNode {
     catch: CatchBlockNode;
 }
 
+export interface KeyBlockNode extends BaseNode {
+    type: 'KeyBlock';
+    expression: Node;
+    children: Node[];
+}
+
 export interface ThenBlockNode extends BaseNode {
     type: 'ThenBlock';
     children: Node[];
@@ -257,6 +263,7 @@ export type Node =
     | ElseBlockNode
     | EachBlockNode
     | AwaitBlockNode
+    | KeyBlockNode
     | ThenBlockNode
     | PendingBlockNode
     | CatchBlockNode

test/printer/samples/key-block.html

@@ -0,0 +1,10 @@
+{#key value}
+    <p>hello</p>
+    <p>hello</p>
+{/key}
+{#key $store}
+    <p>hello</p>
+{/key}
+{#key expr.obj}
+    <p>hello</p>
+{/key}