feat: merge neighboring text and expressions into 1 text node

src/compiler/compile/index.ts

@@ -7,6 +7,7 @@ import { CompileOptions, Warning } from '../interfaces';
 import Component from './Component';
 import fuzzymatch from '../utils/fuzzymatch';
 import get_name_from_filename from './utils/get_name_from_filename';
+import optimise from '../parse/optimise/index';
 
 const valid_options = [
 	'format',
@@ -25,7 +26,8 @@ const valid_options = [
 	'tag',
 	'css',
 	'preserveComments',
-	'preserveWhitespace'
+	'preserveWhitespace',
+	'optimiseAst',
 ];
 
 function validate_options(options: CompileOptions, warnings: Warning[]) {
@@ -57,7 +59,7 @@ function validate_options(options: CompileOptions, warnings: Warning[]) {
 }
 
 export default function compile(source: string, options: CompileOptions = {}) {
-	options = assign({ generate: 'dom', dev: false }, options);
+	options = assign({ generate: 'dom', dev: false, optimiseAst: true }, options);
 
 	const stats = new Stats();
 	const warnings = [];
@@ -68,6 +70,12 @@ export default function compile(source: string, options: CompileOptions = {}) {
 	const ast = parse(source, options);
 	stats.stop('parse');
 
+	if (options.optimiseAst) {
+		stats.start('optimise-ast');
+		optimise(ast);
+		stats.stop('optimise-ast');
+	}
+
 	stats.start('create component');
 	const component = new Component(
 		ast,
@@ -79,9 +87,10 @@ export default function compile(source: string, options: CompileOptions = {}) {
 	);
 	stats.stop('create component');
 
-	const js = options.generate === false
+	const js =
-		? null
+		options.generate === false
-		: options.generate === 'ssr'
+			? null
+			: options.generate === 'ssr'
 			? render_ssr(component, options)
 			: render_dom(component, options);
 

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

@@ -297,6 +297,13 @@ export default class ElementWrapper extends Wrapper {
 					 // @ts-ignore todo: should it be this.fragment.nodes[0].node.data instead?
 					b`${node}.textContent = ${string_literal(this.fragment.nodes[0].data)};`
 				);
+			} else if (
+				this.fragment.nodes.length === 1 && 
+				this.fragment.nodes[0].node.type === 'MustacheTag' && 
+				this.fragment.nodes[0].node.expression.node.type === 'TemplateLiteral') {
+					block.chunks.create.push(
+						b`${node}.textContent = ${this.fragment.nodes[0].node.expression.manipulate(block)};`
+					);
 			} else {
 				const state = {
 					quasi: {

src/compiler/compile/render_dom/wrappers/shared/Tag.ts

@@ -4,6 +4,7 @@ import Renderer from '../../Renderer';
 import Block from '../../Block';
 import MustacheTag from '../../../nodes/MustacheTag';
 import RawMustacheTag from '../../../nodes/RawMustacheTag';
+import { is_string } from './is_string';
 import { Node } from 'estree';
 
 export default class Tag extends Wrapper {
@@ -29,14 +30,20 @@ export default class Tag extends Wrapper {
 		update: ((value: Node) => (Node | Node[]))
 	) {
 		const dependencies = this.node.expression.dynamic_dependencies();
+		const should_extract = this.node.should_cache && dependencies.length > 0;
 		let snippet = this.node.expression.manipulate(block);
+		snippet = is_string(snippet) ? snippet : x`${snippet} + ""`;
+		
+		if (should_extract) {
+			const fn_name = block.get_unique_name(`${this.var.name}_fn`);
+			block.add_variable(fn_name, x`(#ctx) => ${snippet}`);
+			snippet = x`${fn_name}(#ctx)`;
+		}
 
 		const value = this.node.should_cache && block.get_unique_name(`${this.var.name}_value`);
 		const content = this.node.should_cache ? value : snippet;
 
-		snippet = x`${snippet} + ""`;
+		if (this.node.should_cache) block.add_variable(value, snippet);
-
-		if (this.node.should_cache) block.add_variable(value, snippet); // TODO may need to coerce snippet to string
 
 		if (dependencies.length > 0) {
 			let condition = x`#changed.${dependencies[0]}`;

src/compiler/compile/render_dom/wrappers/shared/is_string.ts

@@ -0,0 +1,3 @@
+export function is_string(node) {
+  return node.type === 'TemplateLiteral' || (node.type === 'Literal' && typeof node.value === 'string');
+}

src/compiler/interfaces.ts

@@ -124,6 +124,7 @@ export interface CompileOptions {
 
 	preserveComments?: boolean;
 	preserveWhitespace?: boolean;
+	optimiseAst?: boolean;
 }
 
 export interface ParserOptions {

src/compiler/parse/optimise/index.ts

@@ -0,0 +1,85 @@
+import { walk } from 'estree-walker';
+import { Text, MustacheTag } from '../../interfaces';
+
+export default function optimise(ast) {
+	walk(ast, {
+		enter(node: any) {
+			if (node.type === 'Element') {
+				optimise_text_content(node.children);
+			}
+		},
+	});
+}
+
+const text_like_node_type = new Set(['MustacheTag', 'Text']);
+
+function optimise_text_content(children) {
+	let start = 0;
+	let end = 0;
+
+	do {
+		while (
+			start < children.length &&
+			!text_like_node_type.has(children[start].type)
+		)
+			start++;
+
+		end = start;
+
+		while (end < children.length && text_like_node_type.has(children[end].type))
+			end++;
+
+		if (end > start) {
+			const merged = merge_text_siblings(children.slice(start, end));
+			children.splice(start, end - start, ...merged);
+			start = end;
+		}
+	} while (start < children.length);
+}
+
+function merge_text_siblings(children: Array<Text | MustacheTag>) {
+	if (children.length < 3) {
+		return children;
+	}
+
+	const literal = {
+		type: 'TemplateLiteral',
+		expressions: [],
+		quasis: [],
+	};
+	const state = {
+		quasi: {
+			type: 'TemplateElement',
+			value: { raw: '' },
+			start: children[0].start,
+			end: children[0].start
+		},
+	};
+
+	for (const child of children) {
+		if (child.type === 'MustacheTag') {
+			literal.quasis.push(state.quasi);
+			literal.expressions.push(child.expression);
+			state.quasi = {
+				type: 'TemplateElement',
+				value: { raw: '' },
+				// @ts-ignore
+				start: child.expression.end + 1,
+				// @ts-ignore
+				end: child.expression.end + 1
+			};
+		} else if (child.type === 'Text') {
+			state.quasi.value.raw += child.data;
+			state.quasi.end = child.end;
+		}
+	}
+
+	literal.quasis.push(state.quasi);
+
+	return [{
+		type: 'MustacheTag',
+		expression: literal,
+		start: children[0].start,
+		end: children[children.length - 1].end,
+	}];
+}

test/js/index.js

@@ -36,6 +36,10 @@ describe("js", () => {
 
 			const expected = fs.readFileSync(`${dir}/expected.js`, "utf-8");
 
+			if (process.env.UPDATE_EXPECTED) {
+				fs.writeFileSync(`${dir}/expected.js`, actual);
+			}
+
 			assert.equal(
 				actual.trim().replace(/^[ \t]+$/gm, ""),
 				expected.trim().replace(/^[ \t]+$/gm, "")

test/js/samples/capture-inject-dev-only/expected.js

@@ -24,7 +24,7 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t0 = text(ctx.foo);
+			t0 = text(ctx.foo + "");
 			t1 = space();
 			input = element("input");
 			dispose = listen(input, "input", ctx.input_input_handler);
@@ -37,7 +37,7 @@ function create_fragment(ctx) {
 			set_input_value(input, ctx.foo);
 		},
 		p(changed, ctx) {
-			if (changed.foo) set_data(t0, ctx.foo);
+			if (changed.foo) set_data(t0, ctx.foo + "");
 
 			if (changed.foo && input.value !== ctx.foo) {
 				set_input_value(input, ctx.foo);

test/js/samples/collapses-text-around-comments/expected.js

@@ -26,7 +26,7 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.foo);
+			t = text(ctx.foo + "");
 			attr(p, "class", "svelte-1a7i8ec");
 		},
 		m(target, anchor) {
@@ -34,7 +34,7 @@ function create_fragment(ctx) {
 			append(p, t);
 		},
 		p(changed, ctx) {
-			if (changed.foo) set_data(t, ctx.foo);
+			if (changed.foo) set_data(t, ctx.foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/component-store-access-invalidate/expected.js

@@ -21,14 +21,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t = text(ctx.$foo);
+			t = text(ctx.$foo + "");
 		},
 		m(target, anchor) {
 			insert(target, h1, anchor);
 			append(h1, t);
 		},
 		p(changed, ctx) {
-			if (changed.$foo) set_data(t, ctx.$foo);
+			if (changed.$foo) set_data(t, ctx.$foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/component-store-reassign-invalidate/expected.js

@@ -26,7 +26,7 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t0 = text(ctx.$foo);
+			t0 = text(ctx.$foo + "");
 			t1 = space();
 			button = element("button");
 			button.textContent = "reset";
@@ -39,7 +39,7 @@ function create_fragment(ctx) {
 			insert(target, button, anchor);
 		},
 		p(changed, ctx) {
-			if (changed.$foo) set_data(t0, ctx.$foo);
+			if (changed.$foo) set_data(t0, ctx.$foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/debug-empty/expected.js

@@ -18,18 +18,16 @@ const file = undefined;
 
 function create_fragment(ctx) {
 	let h1;
+	let t0_fn = ctx => `Hello ${ctx.name}!`;
+	let t0_value = t0_fn(ctx);
 	let t0;
 	let t1;
-	let t2;
-	let t3;
 
 	const block = {
 		c: function create() {
 			h1 = element("h1");
-			t0 = text("Hello ");
+			t0 = text(t0_value);
-			t1 = text(ctx.name);
+			t1 = space();
-			t2 = text("!");
-			t3 = space();
 			debugger;
 			add_location(h1, file, 4, 0, 38);
 		},
@@ -39,19 +37,17 @@ function create_fragment(ctx) {
 		m: function mount(target, anchor) {
 			insert_dev(target, h1, anchor);
 			append_dev(h1, t0);
-			append_dev(h1, t1);
+			insert_dev(target, t1, anchor);
-			append_dev(h1, t2);
-			insert_dev(target, t3, anchor);
 		},
 		p: function update(changed, ctx) {
-			if (changed.name) set_data_dev(t1, ctx.name);
+			if (changed.name && t0_value !== (t0_value = t0_fn(ctx))) set_data_dev(t0, t0_value);
 			debugger;
 		},
 		i: noop,
 		o: noop,
 		d: function destroy(detaching) {
 			if (detaching) detach_dev(h1);
-			if (detaching) detach_dev(t3);
+			if (detaching) detach_dev(t1);
 		}
 	};
 

test/js/samples/debug-foo-bar-baz-things/expected.js

@@ -25,7 +25,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_fn = ctx => ctx.thing.name + "";
+	let t0_value = t0_fn(ctx);
 	let t0;
 	let t1;
 
@@ -49,7 +50,7 @@ function create_each_block(ctx) {
 			insert_dev(target, t1, anchor);
 		},
 		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
+			if (changed.things && t0_value !== (t0_value = t0_fn(ctx))) set_data_dev(t0, t0_value);
 
 			if (changed.foo || changed.bar || changed.baz || changed.things) {
 				const { foo, bar, baz, thing } = ctx;
@@ -95,7 +96,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(ctx.foo + "");
 			add_location(p, file, 12, 0, 182);
 		},
 		l: function claim(nodes) {
@@ -135,7 +136,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (changed.foo) set_data_dev(t2, ctx.foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/debug-foo/expected.js

@@ -25,7 +25,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_fn = ctx => ctx.thing.name + "";
+	let t0_value = t0_fn(ctx);
 	let t0;
 	let t1;
 
@@ -49,7 +50,7 @@ function create_each_block(ctx) {
 			insert_dev(target, t1, anchor);
 		},
 		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
+			if (changed.things && t0_value !== (t0_value = t0_fn(ctx))) set_data_dev(t0, t0_value);
 
 			if (changed.foo) {
 				const { foo } = ctx;
@@ -95,7 +96,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(ctx.foo + "");
 			add_location(p, file, 10, 0, 131);
 		},
 		l: function claim(nodes) {
@@ -135,7 +136,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (changed.foo) set_data_dev(t2, ctx.foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/deconflict-builtins/expected.js

@@ -21,7 +21,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.node + "";
+	let t_fn = ctx => ctx.node + "";
+	let t_value = t_fn(ctx);
 	let t;
 
 	return {
@@ -34,7 +35,7 @@ function create_each_block(ctx) {
 			append(span, t);
 		},
 		p(changed, ctx) {
-			if (changed.createElement && t_value !== (t_value = ctx.node + "")) set_data(t, t_value);
+			if (changed.createElement && t_value !== (t_value = t_fn(ctx))) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);

test/js/samples/dev-warning-missing-data-computed/expected.js

@@ -10,7 +10,6 @@ import {
 	noop,
 	safe_not_equal,
 	set_data_dev,
-	space,
 	text
 } from "svelte/internal";
 
@@ -18,17 +17,19 @@ const file = undefined;
 
 function create_fragment(ctx) {
 	let p;
-	let t0_value = Math.max(0, ctx.foo) + "";
+
-	let t0;
+	let t_fn = ctx => `
-	let t1;
+	${Math.max(0, ctx.foo)}
-	let t2;
+	${ctx.bar}
+`;
+
+	let t_value = t_fn(ctx);
+	let t;
 
 	const block = {
 		c: function create() {
 			p = element("p");
-			t0 = text(t0_value);
+			t = text(t_value);
-			t1 = space();
-			t2 = text(ctx.bar);
 			add_location(p, file, 7, 0, 67);
 		},
 		l: function claim(nodes) {
@@ -36,13 +37,10 @@ function create_fragment(ctx) {
 		},
 		m: function mount(target, anchor) {
 			insert_dev(target, p, anchor);
-			append_dev(p, t0);
+			append_dev(p, t);
-			append_dev(p, t1);
-			append_dev(p, t2);
 		},
 		p: function update(changed, ctx) {
-			if (changed.foo && t0_value !== (t0_value = Math.max(0, ctx.foo) + "")) set_data_dev(t0, t0_value);
+			if ((changed.foo || changed.bar) && t_value !== (t_value = t_fn(ctx))) set_data_dev(t, t_value);
-			if (changed.bar) set_data_dev(t2, ctx.bar);
 		},
 		i: noop,
 		o: noop,

test/js/samples/each-block-array-literal/expected.js

@@ -21,7 +21,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.num + "";
+	let t_fn = ctx => ctx.num + "";
+	let t_value = t_fn(ctx);
 	let t;
 
 	return {
@@ -34,7 +35,7 @@ function create_each_block(ctx) {
 			append(span, t);
 		},
 		p(changed, ctx) {
-			if ((changed.a || changed.b || changed.c || changed.d || changed.e) && t_value !== (t_value = ctx.num + "")) set_data(t, t_value);
+			if ((changed.a || changed.b || changed.c || changed.d || changed.e) && t_value !== (t_value = t_fn(ctx))) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);

test/js/samples/each-block-changed-check/expected.js

@@ -28,28 +28,27 @@ function create_each_block(ctx) {
 	let t0;
 	let t1;
 	let span;
-	let t2_value = ctx.comment.author + "";
+
+	let t2_fn = ctx => `
+			${ctx.comment.author} wrote ${ctx.elapsed(ctx.comment.time, ctx.time)} ago:
+		`;
+
+	let t2_value = t2_fn(ctx);
 	let t2;
 	let t3;
-	let t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "";
-	let t4;
-	let t5;
-	let t6;
 	let html_tag;
-	let raw_value = ctx.comment.html + "";
+	let raw_fn = ctx => ctx.comment.html + "";
+	let raw_value = raw_fn(ctx);
 
 	return {
 		c() {
 			div = element("div");
 			strong = element("strong");
-			t0 = text(ctx.i);
+			t0 = text(ctx.i + "");
 			t1 = space();
 			span = element("span");
 			t2 = text(t2_value);
-			t3 = text(" wrote ");
+			t3 = space();
-			t4 = text(t4_value);
-			t5 = text(" ago:");
-			t6 = space();
 			attr(span, "class", "meta");
 			html_tag = new HtmlTag(raw_value, null);
 			attr(div, "class", "comment");
@@ -61,16 +60,12 @@ function create_each_block(ctx) {
 			append(div, t1);
 			append(div, span);
 			append(span, t2);
-			append(span, t3);
+			append(div, t3);
-			append(span, t4);
-			append(span, t5);
-			append(div, t6);
 			html_tag.m(div);
 		},
 		p(changed, ctx) {
-			if (changed.comments && t2_value !== (t2_value = ctx.comment.author + "")) set_data(t2, t2_value);
+			if ((changed.comments || changed.elapsed || changed.time) && t2_value !== (t2_value = t2_fn(ctx))) set_data(t2, t2_value);
-			if ((changed.elapsed || changed.comments || changed.time) && t4_value !== (t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "")) set_data(t4, t4_value);
+			if (changed.comments && raw_value !== (raw_value = raw_fn(ctx))) html_tag.p(raw_value);
-			if (changed.comments && raw_value !== (raw_value = ctx.comment.html + "")) html_tag.p(raw_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);
@@ -97,7 +92,7 @@ function create_fragment(ctx) {
 
 			t0 = space();
 			p = element("p");
-			t1 = text(ctx.foo);
+			t1 = text(ctx.foo + "");
 		},
 		m(target, anchor) {
 			for (let i = 0; i < each_blocks.length; i += 1) {
@@ -132,7 +127,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data(t1, ctx.foo);
+			if (changed.foo) set_data(t1, ctx.foo + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/each-block-keyed-animated/expected.js

@@ -24,7 +24,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_fn = ctx => ctx.thing.name + "";
+	let t_value = t_fn(ctx);
 	let t;
 	let rect;
 	let stop_animation = noop;
@@ -42,7 +43,7 @@ function create_each_block(key_1, ctx) {
 			append(div, t);
 		},
 		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+			if (changed.things && t_value !== (t_value = t_fn(ctx))) set_data(t, t_value);
 		},
 		r() {
 			rect = div.getBoundingClientRect();

test/js/samples/each-block-keyed/expected.js

@@ -22,7 +22,8 @@ function get_each_context(ctx, list, i) {
 
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_fn = ctx => ctx.thing.name + "";
+	let t_value = t_fn(ctx);
 	let t;
 
 	return {
@@ -38,7 +39,7 @@ function create_each_block(key_1, ctx) {
 			append(div, t);
 		},
 		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+			if (changed.things && t_value !== (t_value = t_fn(ctx))) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);

test/js/samples/instrumentation-script-if-no-block/expected.js

@@ -28,7 +28,7 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
+			t3 = text(ctx.x + "");
 			dispose = listen(button, "click", ctx.foo);
 		},
 		m(target, anchor) {
@@ -39,7 +39,7 @@ function create_fragment(ctx) {
 			append(p, t3);
 		},
 		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+			if (changed.x) set_data(t3, ctx.x + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/instrumentation-script-x-equals-x/expected.js

@@ -18,7 +18,8 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_fn = ctx => ctx.things.length + "";
+	let t3_value = t3_fn(ctx);
 	let t3;
 	let dispose;
 
@@ -40,7 +41,7 @@ function create_fragment(ctx) {
 			append(p, t3);
 		},
 		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+			if (changed.things && t3_value !== (t3_value = t3_fn(ctx))) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,

test/js/samples/instrumentation-template-if-no-block/expected.js

@@ -28,7 +28,7 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
+			t3 = text(ctx.x + "");
 			dispose = listen(button, "click", ctx.click_handler);
 		},
 		m(target, anchor) {
@@ -39,7 +39,7 @@ function create_fragment(ctx) {
 			append(p, t3);
 		},
 		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+			if (changed.x) set_data(t3, ctx.x + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/instrumentation-template-x-equals-x/expected.js

@@ -18,7 +18,8 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_fn = ctx => ctx.things.length + "";
+	let t3_value = t3_fn(ctx);
 	let t3;
 	let dispose;
 
@@ -40,7 +41,7 @@ function create_fragment(ctx) {
 			append(p, t3);
 		},
 		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+			if (changed.things && t3_value !== (t3_value = t3_fn(ctx))) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,

test/js/samples/optimise-ast/expected.js

@@ -0,0 +1,65 @@
+import {
+	SvelteComponent,
+	append,
+	detach,
+	element,
+	init,
+	insert,
+	listen,
+	noop,
+	safe_not_equal,
+	set_data,
+	text
+} from "svelte/internal";
+
+function create_fragment(ctx) {
+	let button;
+
+	let t_fn = ctx => `
+	Clicked ${ctx.count} ${ctx.count === 1 ? "time" : "times"}
+`;
+
+	let t_value = t_fn(ctx);
+	let t;
+	let dispose;
+
+	return {
+		c() {
+			button = element("button");
+			t = text(t_value);
+			dispose = listen(button, "click", ctx.increment);
+		},
+		m(target, anchor) {
+			insert(target, button, anchor);
+			append(button, t);
+		},
+		p(changed, ctx) {
+			if (changed.count && t_value !== (t_value = t_fn(ctx))) set_data(t, t_value);
+		},
+		i: noop,
+		o: noop,
+		d(detaching) {
+			if (detaching) detach(button);
+			dispose();
+		}
+	};
+}
+
+function instance($$self, $$props, $$invalidate) {
+	let count = 0;
+
+	function increment() {
+		$$invalidate("count", count = count + 1);
+	}
+
+	return { count, increment };
+}
+
+class Component extends SvelteComponent {
+	constructor(options) {
+		super();
+		init(this, options, instance, create_fragment, safe_not_equal, {});
+	}
+}
+
+export default Component;

test/js/samples/optimise-ast/input.svelte

@@ -0,0 +1,9 @@
+<script>
+	let count = 0;
+	function increment() {
+		count = count + 1;
+	}
+</script>
+<button on:click={increment}>
+	Clicked {count} {count === 1 ? 'time' : 'times'}
+</button>

test/js/samples/unchanged-expression/expected.js

@@ -40,7 +40,7 @@ function create_fragment(ctx) {
 			div1 = element("div");
 			p3 = element("p");
 			t8 = text("Hello ");
-			t9 = text(ctx.world3);
+			t9 = text(ctx.world3 + "");
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
@@ -56,7 +56,7 @@ function create_fragment(ctx) {
 			append(p3, t9);
 		},
 		p(changed, ctx) {
-			if (changed.world3) set_data(t9, ctx.world3);
+			if (changed.world3) set_data(t9, ctx.world3 + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/unreferenced-state-not-invalidated/expected.js

@@ -20,14 +20,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.y);
+			t = text(ctx.y + "");
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t);
 		},
 		p(changed, ctx) {
-			if (changed.y) set_data(t, ctx.y);
+			if (changed.y) set_data(t, ctx.y + "");
 		},
 		i: noop,
 		o: noop,

test/js/samples/window-binding-scroll/expected.js

@@ -31,7 +31,7 @@ function create_fragment(ctx) {
 		c() {
 			p = element("p");
 			t0 = text("scrolled to ");
-			t1 = text(ctx.y);
+			t1 = text(ctx.y + "");
 
 			dispose = listen(window, "scroll", () => {
 				scrolling = true;
@@ -53,7 +53,7 @@ function create_fragment(ctx) {
 				scrolling_timeout = setTimeout(clear_scrolling, 100);
 			}
 
-			if (changed.y) set_data(t1, ctx.y);
+			if (changed.y) set_data(t1, ctx.y + "");
 		},
 		i: noop,
 		o: noop,

test/parser/index.js

@@ -23,9 +23,10 @@ describe('parse', () => {
 			const expectedError = tryToLoadJson(`${__dirname}/samples/${dir}/error.json`);
 
 			try {
-				const { ast } = svelte.compile(input, Object.assign(options, {
+				const { ast } = svelte.compile(
-					generate: false
+					input,
-				}));
+					Object.assign({ optimiseAst: false }, options, { generate: false })
+				);
 
 				fs.writeFileSync(`${__dirname}/samples/${dir}/_actual.json`, JSON.stringify(ast, null, '\t'));
 

test/parser/samples/optimised-ast-text-content/input.svelte

@@ -0,0 +1,4 @@
+<script>let name;</script>
+<div>Hello {name}!</div>
+<div>Hello <span>{name}</span>!</div>
+<div><span>Hello</span> {name}!</div>

test/parser/samples/optimised-ast-text-content/options.json

@@ -0,0 +1 @@
+{ "optimiseAst": true }

test/parser/samples/optimised-ast-text-content/output.json

@@ -0,0 +1,249 @@
+{
+	"html": {
+		"start": 27,
+		"end": 127,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 26,
+				"end": 27,
+				"type": "Text",
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"start": 27,
+				"end": 51,
+				"type": "Element",
+				"name": "div",
+				"attributes": [],
+				"children": [
+					{
+						"type": "MustacheTag",
+						"expression": {
+							"type": "TemplateLiteral",
+							"expressions": [
+								{
+									"type": "Identifier",
+									"start": 39,
+									"end": 43,
+									"name": "name"
+								}
+							],
+							"quasis": [
+								{
+									"type": "TemplateElement",
+									"value": {
+										"raw": "Hello "
+									},
+									"start": 32,
+									"end": 38
+								},
+								{
+									"type": "TemplateElement",
+									"value": {
+										"raw": "!"
+									},
+									"start": 44,
+									"end": 45
+								}
+							]
+						},
+						"start": 32,
+						"end": 45
+					}
+				]
+			},
+			{
+				"start": 51,
+				"end": 52,
+				"type": "Text",
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"start": 52,
+				"end": 89,
+				"type": "Element",
+				"name": "div",
+				"attributes": [],
+				"children": [
+					{
+						"start": 57,
+						"end": 63,
+						"type": "Text",
+						"raw": "Hello ",
+						"data": "Hello "
+					},
+					{
+						"start": 63,
+						"end": 82,
+						"type": "Element",
+						"name": "span",
+						"attributes": [],
+						"children": [
+							{
+								"start": 69,
+								"end": 75,
+								"type": "MustacheTag",
+								"expression": {
+									"type": "Identifier",
+									"start": 70,
+									"end": 74,
+									"name": "name"
+								}
+							}
+						]
+					},
+					{
+						"start": 82,
+						"end": 83,
+						"type": "Text",
+						"raw": "!",
+						"data": "!"
+					}
+				]
+			},
+			{
+				"start": 89,
+				"end": 90,
+				"type": "Text",
+				"raw": "\n",
+				"data": "\n"
+			},
+			{
+				"start": 90,
+				"end": 127,
+				"type": "Element",
+				"name": "div",
+				"attributes": [],
+				"children": [
+					{
+						"start": 95,
+						"end": 113,
+						"type": "Element",
+						"name": "span",
+						"attributes": [],
+						"children": [
+							{
+								"start": 101,
+								"end": 106,
+								"type": "Text",
+								"raw": "Hello",
+								"data": "Hello"
+							}
+						]
+					},
+					{
+						"type": "MustacheTag",
+						"expression": {
+							"type": "TemplateLiteral",
+							"expressions": [
+								{
+									"type": "Identifier",
+									"start": 115,
+									"end": 119,
+									"name": "name"
+								}
+							],
+							"quasis": [
+								{
+									"type": "TemplateElement",
+									"value": {
+										"raw": " "
+									},
+									"start": 113,
+									"end": 114
+								},
+								{
+									"type": "TemplateElement",
+									"value": {
+										"raw": "!"
+									},
+									"start": 120,
+									"end": 121
+								}
+							]
+						},
+						"start": 113,
+						"end": 121
+					}
+				]
+			}
+		]
+	},
+	"instance": {
+		"type": "Script",
+		"start": 0,
+		"end": 26,
+		"context": "default",
+		"content": {
+			"type": "Program",
+			"start": 8,
+			"end": 17,
+			"loc": {
+				"start": {
+					"line": 1,
+					"column": 0
+				},
+				"end": {
+					"line": 1,
+					"column": 17
+				}
+			},
+			"body": [
+				{
+					"type": "VariableDeclaration",
+					"start": 8,
+					"end": 17,
+					"loc": {
+						"start": {
+							"line": 1,
+							"column": 8
+						},
+						"end": {
+							"line": 1,
+							"column": 17
+						}
+					},
+					"declarations": [
+						{
+							"type": "VariableDeclarator",
+							"start": 12,
+							"end": 16,
+							"loc": {
+								"start": {
+									"line": 1,
+									"column": 12
+								},
+								"end": {
+									"line": 1,
+									"column": 16
+								}
+							},
+							"id": {
+								"type": "Identifier",
+								"start": 12,
+								"end": 16,
+								"loc": {
+									"start": {
+										"line": 1,
+										"column": 12
+									},
+									"end": {
+										"line": 1,
+										"column": 16
+									}
+								},
+								"name": "name"
+							},
+							"init": null
+						}
+					],
+					"kind": "let"
+				}
+			],
+			"sourceType": "module"
+		}
+	}
+}

test/runtime/samples/optimise-ast/_config.js

@@ -0,0 +1,12 @@
+export default {
+	html: `<button>Clicked 0 times</button>`,
+	async test({ assert, target, window }) {
+		const buttons = target.querySelectorAll('button');
+		const event = new window.MouseEvent('click');
+		await buttons[0].dispatchEvent(event);
+		assert.htmlEqual(target.innerHTML, `<button>Clicked 1 time</button>`);
+
+		await buttons[0].dispatchEvent(event);
+		assert.htmlEqual(target.innerHTML, `<button>Clicked 2 times</button>`);
+	},
+};

test/runtime/samples/optimise-ast/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	let count = 0;
+	function increment() {
+		count = count + 1;
+	}
+</script>
+<button on:click={increment}>
+	Clicked {count} {count === 1 ? 'time' : 'times'}
+</button>

test/sourcemaps/samples/basic/test.js

@@ -1,26 +1,9 @@
 export function test({ assert, smc, locateInSource, locateInGenerated }) {
 	const expected = locateInSource( 'foo.bar.baz' );
 
-	let start;
+	const start = locateInGenerated('foo.bar.baz');
-	let actual;
 
-	start = locateInGenerated('foo.bar.baz');
+	const actual = smc.originalPositionFor({
-
-	actual = smc.originalPositionFor({
-		line: start.line + 1,
-		column: start.column
-	});
-
-	assert.deepEqual( actual, {
-		source: 'input.svelte',
-		name: null,
-		line: expected.line + 1,
-		column: expected.column
-	});
-
-	start = locateInGenerated( 'foo.bar.baz', start.character + 1 );
-
-	actual = smc.originalPositionFor({
 		line: start.line + 1,
 		column: start.column
 	});