preserve js comments where possible (#4293)

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Allow access to `let:` variables in sibling attributes on slot root ([#4173](https://github.com/sveltejs/svelte/issues/4173))
 * Fix `~=` and class selector matching against values separated by any whitespace characters ([#4242](https://github.com/sveltejs/svelte/issues/4242))
 * Fix code generation for `await`ed expressions that need parentheses ([#4267](https://github.com/sveltejs/svelte/issues/4267))
+* Preserve JavaScript comments from the original component source where possible ([#4268](https://github.com/sveltejs/svelte/issues/4268))
 * Add some more known globals ([#4276](https://github.com/sveltejs/svelte/pull/4276))
 * Correctly apply event modifiers to `<svelte:body>` events ([#4278](https://github.com/sveltejs/svelte/issues/4278))
 

package-lock.json

@@ -597,9 +597,9 @@
       "dev": true
     },
     "code-red": {
-      "version": "0.0.30",
-      "resolved": "https://registry.npmjs.org/code-red/-/code-red-0.0.30.tgz",
-      "integrity": "sha512-nsScy3A59tbV5uzndcedIEGHmdWNEByJrC7DUyb0Wh7qZcoPfAlcYsr0ZINkAEhZofSI26F1mi+lRO0/6EV2/g==",
+      "version": "0.0.31",
+      "resolved": "https://registry.npmjs.org/code-red/-/code-red-0.0.31.tgz",
+      "integrity": "sha512-7Gf3vm8pDbs+H/hKsaqOZe0xKlE9Neah12GCfs7qun3fBUaOXwexAMjn0Eo9cvJJvhRMaL0jgPiY9ZGLTWoe8A==",
       "dev": true,
       "requires": {
         "acorn": "^7.1.0",

package.json

@@ -70,7 +70,7 @@
     "acorn": "^7.1.0",
     "agadoo": "^1.1.0",
     "c8": "^5.0.1",
-    "code-red": "0.0.30",
+    "code-red": "0.0.31",
     "codecov": "^3.5.0",
     "css-tree": "1.0.0-alpha22",
     "eslint": "^6.3.0",

src/compiler/parse/acorn.ts

@@ -1,14 +1,13 @@
-import * as acorn from 'acorn';
+import { Node } from 'acorn';
+import * as code_red from 'code-red';
 
-const Parser = acorn.Parser;
-
-export const parse = (source: string) => Parser.parse(source, {
+export const parse = (source: string): Node => code_red.parse(source, {
 	sourceType: 'module',
 	ecmaVersion: 11,
 	locations: true
 });
 
-export const parse_expression_at = (source: string, index: number) => Parser.parseExpressionAt(source, index, {
+export const parse_expression_at = (source: string, index: number): Node => code_red.parseExpressionAt(source, index, {
 	ecmaVersion: 11,
 	locations: true
 });

test/js/samples/action-custom-event-handler/expected.js

@@ -43,7 +43,7 @@ function handleFoo(bar) {
 
 function foo(node, callback) {
 	
-}
+} // code goes here
 
 function instance($$self, $$props, $$invalidate) {
 	let { bar } = $$props;

test/js/samples/event-modifiers/expected.js

@@ -63,11 +63,11 @@ function create_fragment(ctx) {
 
 function handleTouchstart() {
 	
-}
+} // ...
 
 function handleClick() {
 	
-}
+} // ...
 
 class Component extends SvelteComponent {
 	constructor(options) {

test/js/samples/ssr-no-oncreate-etc/expected.js

@@ -13,7 +13,7 @@ function foo() {
 
 function swipe(node, callback) {
 	
-}
+} // TODO implement
 
 const Component = create_ssr_component(($$result, $$props, $$bindings, $$slots) => {
 	onMount(() => {

test/parser/samples/script-comment-only/output.json

@@ -41,7 +41,15 @@
 				}
 			},
 			"body": [],
-			"sourceType": "module"
+			"sourceType": "module",
+			"trailingComments": [
+				{
+					"type": "Line",
+					"value": " TODO write some code",
+					"start": 10,
+					"end": 33
+				}
+			]
 		}
 	}
 }

test/parser/samples/script-comment-trailing-multiline/output.json

@@ -134,7 +134,15 @@
 					"kind": "let"
 				}
 			],
-			"sourceType": "module"
+			"sourceType": "module",
+			"trailingComments": [
+				{
+					"type": "Block",
+					"value": "\n\ttrailing multiline comment\n",
+					"start": 32,
+					"end": 67
+				}
+			]
 		}
 	}
 }

test/parser/samples/script-comment-trailing/output.json

@@ -134,7 +134,15 @@
 					"kind": "let"
 				}
 			],
-			"sourceType": "module"
+			"sourceType": "module",
+			"trailingComments": [
+				{
+					"type": "Line",
+					"value": " trailing line comment",
+					"start": 32,
+					"end": 56
+				}
+			]
 		}
 	}
 }