From 7d4990c5d47eec078548fa806d61cac5687edc07 Mon Sep 17 00:00:00 2001
From: yosuke ota <otameshiyo23@gmail.com>
Date: Mon, 11 Apr 2022 09:50:56 +0900
Subject: [PATCH] Strip newline logic to src/compiler/compile/nodes/Eleement.ts

---
 src/compiler/compile/nodes/Element.ts            | 16 ++++++++++------
 src/compiler/compile/nodes/Text.ts               |  9 ---------
 .../compile/render_dom/wrappers/Fragment.ts      |  3 ---
 .../compile/render_ssr/handlers/Element.ts       | 10 ++++++++++
 .../samples/pre-tag/_expected.html               | 12 ++++--------
 5 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/src/compiler/compile/nodes/Element.ts b/src/compiler/compile/nodes/Element.ts
index 4ca28ca736..55b7fbfb9d 100644
--- a/src/compiler/compile/nodes/Element.ts
+++ b/src/compiler/compile/nodes/Element.ts
@@ -198,6 +198,16 @@ export default class Element extends Node {
 		this.namespace = get_namespace(parent as Element, this, component.namespace);
 
 		if (this.namespace !== namespaces.foreign) {
+			if (this.name === 'pre' || this.name === 'textarea') {
+				const first = info.children[0];
+				if (first && first.type === 'Text') {
+					// The leading newline character should be stripped.
+					// see https://html.spec.whatwg.org/multipage/syntax.html#element-restrictions
+					// see https://html.spec.whatwg.org/multipage/grouping-content.html#the-pre-element
+					first.data = first.data.replace(start_newline, '');
+				}
+			}
+
 			if (this.name === 'textarea') {
 				if (info.children.length > 0) {
 					const value_attribute = info.attributes.find(node => node.name === 'value');
@@ -208,12 +218,6 @@ export default class Element extends Node {
 
 					// this is an egregious hack, but it's the easiest way to get <textarea>
 					// children treated the same way as a value attribute
-					const first = info.children[0];
-					if (first && first.type === 'Text') {
-						// The leading newline character should be stripped.
-						// see https://html.spec.whatwg.org/multipage/syntax.html#element-restrictions
-						first.data = first.data.replace(start_newline, '');
-					}
 					info.attributes.push({
 						type: 'Attribute',
 						name: 'value',
diff --git a/src/compiler/compile/nodes/Text.ts b/src/compiler/compile/nodes/Text.ts
index 1c5a6a7584..347beb9c23 100644
--- a/src/compiler/compile/nodes/Text.ts
+++ b/src/compiler/compile/nodes/Text.ts
@@ -49,15 +49,6 @@ export default class Text extends Node {
 		return this.within_pre();
 	}
 
-	/**
-	 * @returns If true, the leading newline character should be stripped.
-	 * @see https://html.spec.whatwg.org/multipage/grouping-content.html#the-pre-element
-	 */
-	should_strip_leading_newline(): boolean {
-		const parent = this.parent;
-		return parent.type === 'Element' && parent.name === 'pre' && parent.children[0] === this;
-	}
-
 	within_pre(): boolean {
 		let node = this.parent;
 		while (node) {
diff --git a/src/compiler/compile/render_dom/wrappers/Fragment.ts b/src/compiler/compile/render_dom/wrappers/Fragment.ts
index 7986e43c83..de77dfc7c5 100644
--- a/src/compiler/compile/render_dom/wrappers/Fragment.ts
+++ b/src/compiler/compile/render_dom/wrappers/Fragment.ts
@@ -21,7 +21,6 @@ import Block from '../Block';
 import { trim_start, trim_end } from '../../../utils/trim';
 import { link } from '../../../utils/link';
 import { Identifier } from 'estree';
-import { start_newline } from '../../../utils/patterns';
 
 const wrappers = {
 	AwaitBlock,
@@ -131,8 +130,6 @@ export default class FragmentWrapper {
 			if (first && first.node.type === 'Text') {
 				if (!first.node.keep_space()) {
 					first.data = trim_start(first.data);
-				} else if (first.node.should_strip_leading_newline()) {
-					first.data = first.data.replace(start_newline, '');
 				}
 				if (!first.data) {
 					first.var = null;
diff --git a/src/compiler/compile/render_ssr/handlers/Element.ts b/src/compiler/compile/render_ssr/handlers/Element.ts
index fc05cbb74a..ebc18e17cd 100644
--- a/src/compiler/compile/render_ssr/handlers/Element.ts
+++ b/src/compiler/compile/render_ssr/handlers/Element.ts
@@ -8,6 +8,7 @@ import Expression from '../../nodes/shared/Expression';
 import remove_whitespace_children from './utils/remove_whitespace_children';
 import fix_attribute_casing from '../../render_dom/wrappers/Element/fix_attribute_casing';
 import { namespaces } from '../../../utils/namespaces';
+import { start_newline } from '../../../utils/patterns';
 
 export default function(node: Element, renderer: Renderer, options: RenderOptions) {
 
@@ -176,6 +177,15 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 			renderer.add_string(`</${node.name}>`);
 		}
 	} else {
+		if (node.name === 'pre') {
+			// Two or more leading newlines are required to restore the leading newline immediately after `<pre>`.
+			// see https://html.spec.whatwg.org/multipage/grouping-content.html#the-pre-element
+			// see https://html.spec.whatwg.org/multipage/syntax.html#element-restrictions
+			const first = children[0];
+			if (first && first.type === 'Text' && start_newline.test(first.data)) {
+				renderer.add_string('\n');
+			}
+		}
 		renderer.render(children, options);
 
 		if (!is_void(node.name)) {
diff --git a/test/server-side-rendering/samples/pre-tag/_expected.html b/test/server-side-rendering/samples/pre-tag/_expected.html
index 8d8ad5497d..5459102786 100644
--- a/test/server-side-rendering/samples/pre-tag/_expected.html
+++ b/test/server-side-rendering/samples/pre-tag/_expected.html
@@ -1,5 +1,4 @@
-<pre>
-  A
+<pre>  A
   B
   <span>
     C
@@ -18,8 +17,7 @@
   F
 </div>
 
-<div><pre>
-    A
+<div><pre>    A
     B
     <span>
       C
@@ -29,10 +27,8 @@
     F
   </pre></div>
 
-<div id="pre-with-leading-newline"><pre>
-leading newline</pre>
-  <pre>
-  leading newline and spaces</pre>
+<div id="pre-with-leading-newline"><pre>leading newline</pre>
+  <pre>  leading newline and spaces</pre>
   <pre>
 
 leading newlines</pre></div>