prevent top-level text being discarded - fixes #3027

src/compiler/compile/nodes/Text.ts

@@ -6,7 +6,6 @@ import { INode } from './interfaces';
 export default class Text extends Node {
 	type: 'Text';
 	data: string;
-	use_space = false;
 
 	constructor(component: Component, parent: INode, scope: TemplateScope, info: any) {
 		super(component, parent, scope, info);
@@ -20,8 +19,6 @@ export default class Text extends Node {
 				}
 				node = node.parent;
 			}
-
-			this.use_space = true;
 		}
 	}
 }

src/compiler/compile/render_dom/wrappers/Element/index.ts

@@ -335,7 +335,7 @@ export default class ElementWrapper extends Wrapper {
 
 		function to_html(wrapper: ElementWrapper | TextWrapper) {
 			if (wrapper.node.type === 'Text') {
-				if (wrapper.node.use_space) return ' ';
+				if ((wrapper as TextWrapper).use_space()) return ' ';
 
 				const parent = wrapper.node.parent as Element;
 

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

@@ -17,6 +17,7 @@ import { INode } from '../../nodes/interfaces';
 import Renderer from '../Renderer';
 import Block from '../Block';
 import { trim_start, trim_end } from '../../../utils/trim';
+import TextWrapper from './Text';
 
 const wrappers = {
 	AwaitBlock,
@@ -91,8 +92,7 @@ export default class FragmentWrapper {
 				// *unless* there is no whitespace between this node and its next sibling
 				if (this.nodes.length === 0) {
 					const should_trim = (
-						// @ts-ignore todo: probably error, should it be next_sibling.node.data?
-						next_sibling ? (next_sibling.node.type === 'Text' && /^\s/.test(next_sibling.data) && trimmable_at(child, next_sibling)) : !child.has_ancestor('EachBlock')
+						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) {
@@ -103,8 +103,7 @@ export default class FragmentWrapper {
 
 				// glue text nodes (which could e.g. be separated by comments) together
 				if (last_child && last_child.node.type === 'Text') {
-					// @ts-ignore todo: probably error, should it be last_child.node.data?
-					last_child.data = data + last_child.data;
+					(last_child as TextWrapper).data = data + (last_child as TextWrapper).data;
 					continue;
 				}
 

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

@@ -49,12 +49,27 @@ export default class TextWrapper extends Wrapper {
 		this.var = this.skip ? null : 't';
 	}
 
+	use_space() {
+		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;
+	}
+
 	render(block: Block, parent_node: string, parent_nodes: string) {
 		if (this.skip) return;
 
 		block.add_element(
 			this.var,
-			this.node.use_space ? `@space()` : `@text(${stringify(this.data)})`,
+			this.use_space() ? `@space()` : `@text(${stringify(this.data)})`,
 			parent_nodes && `@claim_text(${parent_nodes}, ${stringify(this.data)})`,
 			parent_node
 		);

test/runtime/samples/isolated-text/_config.js

@@ -0,0 +1,6 @@
+export default {
+	html: `
+		before
+		<h1>after</h1>
+	`
+};

test/runtime/samples/isolated-text/main.svelte

@@ -0,0 +1,5 @@
+before
+
+<!---->
+
+<h1>after</h1>