From 62b9d02f6fbb08d51bed73f33435c1ed83d5b2ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barth=C3=A9l=C3=A9my=20Ledoux?= <ledouxb@me.com>
Date: Mon, 17 Aug 2020 10:20:28 -0500
Subject: [PATCH] feat(compiler-core): add `comments` parser option (#1858)

---
 packages/compiler-core/__tests__/parse.spec.ts | 10 ++++++++++
 packages/compiler-core/src/options.ts          |  4 ++++
 packages/compiler-core/src/parse.ts            | 11 ++++++++---
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/packages/compiler-core/__tests__/parse.spec.ts b/packages/compiler-core/__tests__/parse.spec.ts
index 7f12a700..56bea060 100644
--- a/packages/compiler-core/__tests__/parse.spec.ts
+++ b/packages/compiler-core/__tests__/parse.spec.ts
@@ -374,6 +374,16 @@ describe('compiler: parse', () => {
         }
       })
     })
+
+    test('comments option', () => {
+      __DEV__ = false
+      const astNoComment = baseParse('<!--abc-->')
+      const astWithComments = baseParse('<!--abc-->', { comments: true })
+      __DEV__ = true
+
+      expect(astNoComment.children).toHaveLength(0)
+      expect(astWithComments.children).toHaveLength(1)
+    })
   })
 
   describe('Element', () => {
diff --git a/packages/compiler-core/src/options.ts b/packages/compiler-core/src/options.ts
index f0d5258c..22d8a086 100644
--- a/packages/compiler-core/src/options.ts
+++ b/packages/compiler-core/src/options.ts
@@ -49,6 +49,10 @@ export interface ParserOptions {
    */
   decodeEntities?: (rawText: string, asAttr: boolean) => string
   onError?: (error: CompilerError) => void
+  /**
+   * Keep comments in the templates AST, even in production
+   */
+  comments?: boolean
 }
 
 export type HoistTransform = (
diff --git a/packages/compiler-core/src/parse.ts b/packages/compiler-core/src/parse.ts
index e2888e32..60d60427 100644
--- a/packages/compiler-core/src/parse.ts
+++ b/packages/compiler-core/src/parse.ts
@@ -50,7 +50,8 @@ export const defaultParserOptions: MergedParserOptions = {
   isCustomElement: NO,
   decodeEntities: (rawText: string): string =>
     rawText.replace(decodeRE, (_, p1) => decodeMap[p1]),
-  onError: defaultOnError
+  onError: defaultOnError,
+  comments: false
 }
 
 export const enum TextModes {
@@ -228,8 +229,12 @@ function parseChildren(
           } else {
             node.content = node.content.replace(/[\t\r\n\f ]+/g, ' ')
           }
-        } else if (!__DEV__ && node.type === NodeTypes.COMMENT) {
-          // remove comment nodes in prod
+        } else if (
+          !__DEV__ &&
+          node.type === NodeTypes.COMMENT &&
+          !context.options.comments
+        ) {
+          // remove comment nodes in prod by default
           removedWhitespace = true
           nodes[i] = null as any
         }