[fix]: keep space in `<pre>` or when `preserveWhitespace: true` (#6990)

Fixes #6437
Fixes #4731
Closes #4737

Whitespace is now untouched inside <pre> tag and other tags if preserveWhitespace is true

src/compiler/compile/nodes/Text.ts

@@ -43,4 +43,21 @@ export default class Text extends Node {
 
 		return parent_element.namespace || elements_without_text.has(parent_element.name);
 	}
+
+	keep_space(): boolean {
+		if (this.component.component_options.preserveWhitespace) return true;
+		return this.within_pre();
+	}
+
+	within_pre(): boolean {
+		let node = this.parent;
+		while (node) {
+			if (node.type === 'Element' && node.name === 'pre') {
+				return true;
+			}
+			node = node.parent;
+		}
+
+		return false;
+	}
 }

src/compiler/compile/render_dom/wrappers/Fragment.ts

@@ -95,7 +95,7 @@ export default class FragmentWrapper {
 						next_sibling ? (next_sibling.node.type === 'Text' && /^\s/.test(next_sibling.node.data) && trimmable_at(child, next_sibling)) : !child.has_ancestor('EachBlock')
 					);
 
-					if (should_trim) {
+					if (should_trim && !child.keep_space()) {
 						data = trim_end(data);
 						if (!data) continue;
 					}
@@ -127,7 +127,7 @@ export default class FragmentWrapper {
 		if (strip_whitespace) {
 			const first = this.nodes[0] as Text;
 
-			if (first && first.node.type === 'Text') {
+			if (first && first.node.type === 'Text' && !first.node.keep_space()) {
 				first.data = trim_start(first.data);
 				if (!first.data) {
 					first.var = null;

src/compiler/compile/render_dom/wrappers/Text.ts

@@ -29,15 +29,7 @@ export default class TextWrapper extends Wrapper {
 		if (this.renderer.component.component_options.preserveWhitespace) return false;
 		if (/[\S\u00A0]/.test(this.data)) return false;
 
-		let node = this.parent && this.parent.node;
-		while (node) {
-			if (node.type === 'Element' && node.name === 'pre') {
-				return false;
-			}
-			node = node.parent;
-		}
-
-		return true;
+		return !this.node.within_pre();
 	}
 
 	render(block: Block, parent_node: Identifier, parent_nodes: Identifier) {

src/compiler/compile/render_ssr/handlers/utils/remove_whitespace_children.ts

@@ -26,7 +26,7 @@ export default function remove_whitespace_children(children: INode[], next?: INo
 					  trimmable_at(child, next)
 					: !child.has_ancestor('EachBlock');
 
-				if (should_trim) {
+				if (should_trim && !child.keep_space()) {
 					data = trim_end(data);
 					if (!data) continue;
 				}
@@ -47,7 +47,7 @@ export default function remove_whitespace_children(children: INode[], next?: INo
 	}
 
 	const first = nodes[0];
-	if (first && first.type === 'Text') {
+	if (first && first.type === 'Text' && !first.keep_space()) {
 		first.data = trim_start(first.data);
 		if (!first.data) {
 			first.var = null;

test/runtime/samples/pre-tag/_config.js

@@ -0,0 +1,57 @@
+export default {
+	test({ assert, target }) {
+		// Test for <pre> tag
+		const elementPre = target.querySelector('#pre');
+		// Test for non <pre> tag
+		const elementDiv = target.querySelector('#div');
+		// Test for <pre> tag in non <pre> tag
+		const elementDivWithPre = target.querySelector('#div-with-pre');
+
+		// There is a slight difference in innerHTML because there is a difference in HTML optimization (in jsdom)
+		// depending on how the innerHTML is set.
+		// (There is no difference in the display.)
+		// Reassign innerHTML to add the same optimizations to innerHTML.
+
+		// eslint-disable-next-line no-self-assign
+		elementPre.innerHTML = elementPre.innerHTML;
+		// eslint-disable-next-line no-self-assign
+		elementDiv.innerHTML = elementDiv.innerHTML;
+		// eslint-disable-next-line no-self-assign
+		elementDivWithPre.innerHTML = elementDivWithPre.innerHTML;
+
+		assert.equal(
+			elementPre.innerHTML,
+			`
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+`
+		);
+		assert.equal(
+			elementDiv.innerHTML,
+			`A
+  B
+  <span>C
+    D</span>
+  E
+  F`
+		);
+		assert.equal(
+			elementDivWithPre.innerHTML,
+			`<pre>    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>`
+		);
+	}
+};

test/runtime/samples/pre-tag/main.svelte

@@ -0,0 +1,34 @@
+<pre id="pre">
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div id="div">
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div id="div-with-pre">
+  <pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+</div>

test/runtime/samples/preserve-whitespaces/_config.js

@@ -0,0 +1,66 @@
+export default {
+	compileOptions: {
+		preserveWhitespace: true
+	},
+	test({ assert, target }) {
+		// Test for <pre> tag
+		const elementPre = target.querySelector('#pre');
+		// Test for non <pre> tag
+		const elementDiv = target.querySelector('#div');
+		// Test for <pre> tag in non <pre> tag
+		const elementDivWithPre = target.querySelector('#div-with-pre');
+
+		// There is a slight difference in innerHTML because there is a difference in HTML optimization (in jsdom)
+		// depending on how the innerHTML is set.
+		// (There is no difference in the display.)
+		// Reassign innerHTML to add the same optimizations to innerHTML.
+
+		// eslint-disable-next-line no-self-assign
+		elementPre.innerHTML = elementPre.innerHTML;
+		// eslint-disable-next-line no-self-assign
+		elementDiv.innerHTML = elementDiv.innerHTML;
+		// eslint-disable-next-line no-self-assign
+		elementDivWithPre.innerHTML = elementDivWithPre.innerHTML;
+
+		assert.equal(
+			elementPre.innerHTML,
+			`
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+`
+		);
+		assert.equal(
+			elementDiv.innerHTML,
+			`
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+`
+		);
+		assert.equal(
+			elementDivWithPre.innerHTML,
+			`
+  <pre>    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+`
+		);
+	}
+};

test/runtime/samples/preserve-whitespaces/main.svelte

@@ -0,0 +1,34 @@
+<pre id="pre">
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div id="div">
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div id="div-with-pre">
+  <pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+</div>

test/server-side-rendering/index.ts

@@ -83,9 +83,13 @@ describe('ssr', () => {
 				if (css.code) fs.writeFileSync(`${dir}/_actual.css`, css.code);
 
 				try {
+					if (config.withoutNormalizeHtml) {
+						assert.strictEqual(html.trim(), expectedHtml.trim().replace(/\r\n/g, '\n'));
+					} else {
 						(compileOptions.preserveComments
 							? assert.htmlEqualWithComments
 							: assert.htmlEqual)(html, expectedHtml);
+					}
 				} catch (error) {
 					if (shouldUpdateExpected()) {
 						fs.writeFileSync(`${dir}/_expected.html`, html);

test/server-side-rendering/samples/pre-tag/_config.js

@@ -0,0 +1,3 @@
+export default {
+	withoutNormalizeHtml: true
+};

test/server-side-rendering/samples/pre-tag/_expected.html

@@ -0,0 +1,30 @@
+<pre>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div>A
+  B
+  <span>C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div><pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre></div>

test/server-side-rendering/samples/pre-tag/main.svelte

@@ -0,0 +1,34 @@
+<pre>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div>
+  <pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+</div>

test/server-side-rendering/samples/preserve-whitespaces/_config.js

@@ -0,0 +1,6 @@
+export default {
+	withoutNormalizeHtml: true,
+	compileOptions: {
+		preserveWhitespace: true
+	}
+};

test/server-side-rendering/samples/preserve-whitespaces/_expected.html

@@ -0,0 +1,34 @@
+<pre>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div>
+  <pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+</div>

test/server-side-rendering/samples/preserve-whitespaces/main.svelte

@@ -0,0 +1,34 @@
+<pre>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</pre>
+
+<div>
+  A
+  B
+  <span>
+    C
+    D
+  </span>
+  E
+  F
+</div>
+
+<div>
+  <pre>
+    A
+    B
+    <span>
+      C
+      D
+    </span>
+    E
+    F
+  </pre>
+</div>