add loopGuardTimeout options

site/content/docs/04-compile-time.md

@@ -53,6 +53,7 @@ The following options can be passed to the compiler. None are required:
 | `tag` | string | null
 | `accessors` | boolean | `false`
 | `css` | boolean | `true`
+| `loopGuardTimeout` | number | 0
 | `preserveComments` | boolean | `false`
 | `preserveWhitespace` | boolean | `false`
 | `outputFilename` | string | `null`
@@ -73,6 +74,7 @@ The following options can be passed to the compiler. None are required:
 | `customElement` | `false` | If `true`, tells the compiler to generate a custom element constructor instead of a regular Svelte component.
 | `tag` | `null` | A `string` that tells Svelte what tag name to register the custom element with. It must be a lowercase alphanumeric string with at least one hyphen, e.g. `"my-element"`.
 | `css` | `true` | If `true`, styles will be included in the JavaScript class and injected at runtime. It's recommended that you set this to `false` and use the CSS that is statically generated, as it will result in smaller JavaScript bundles and better performance.
+| `loopGuardTimeout` | 0 | A `number` that tells Svelte to break the loop if it blocks the thread for more than `loopGuardTimeout` ms. This is useful to prevent infinite loops. **Only available when `dev: true`**
 | `preserveComments` | `false` | If `true`, your HTML comments will be preserved during server-side rendering. By default, they are stripped out.
 | `preserveWhitespace` | `false` | If `true`, whitespace inside and between elements is kept as you typed it, rather than optimised by Svelte.
 | `outputFilename` | `null` | A `string` used for your JavaScript sourcemap.

src/compiler/compile/Component.ts

@@ -750,8 +750,8 @@ export default class Component {
 
 				component.warn_on_undefined_store_value_references(node, parent, scope);
 
-				if (component.compile_options.dev) {
-					const to_insert_for_loop_protect = component.loop_protect(node, prop, index);
+				if (component.compile_options.dev && component.compile_options.loopGuardTimeout > 0) {
+					const to_insert_for_loop_protect = component.loop_protect(node, prop, index, component.compile_options.loopGuardTimeout);
 					if (to_insert_for_loop_protect) {
 						if (!Array.isArray(parent[prop])) {
 							parent[prop] = {
@@ -863,7 +863,7 @@ export default class Component {
 		}
 	}
 
-	loop_protect(node, prop, index) {
+	loop_protect(node, prop, index, timeout) {
 		if (node.type === 'WhileStatement' ||
 			node.type === 'ForStatement' ||
 			node.type === 'DoWhileStatement') {
@@ -873,7 +873,7 @@ export default class Component {
 				internal: true,
 			});
 
-			const before = b`const ${guard} = @loop_guard()`;
+			const before = b`const ${guard} = @loop_guard(${timeout})`;
 			const inside = b`${guard}();`;
 
 			// wrap expression statement with BlockStatement

src/compiler/compile/index.ts

@@ -24,12 +24,13 @@ const valid_options = [
 	'customElement',
 	'tag',
 	'css',
+	'loopGuardTimeout',
 	'preserveComments',
 	'preserveWhitespace'
 ];
 
 function validate_options(options: CompileOptions, warnings: Warning[]) {
-	const { name, filename } = options;
+	const { name, filename, loopGuardTimeout, dev } = options;
 
 	Object.keys(options).forEach(key => {
 		if (valid_options.indexOf(key) === -1) {
@@ -54,6 +55,16 @@ function validate_options(options: CompileOptions, warnings: Warning[]) {
 			toString: () => message,
 		});
 	}
+
+	if (loopGuardTimeout && !dev) {
+		const message = 'options.loopGuardTimeout is for options.dev = true only';
+		warnings.push({
+			code: `options-loop-guard-timeout`,
+			message,
+			filename,
+			toString: () => message,
+		});
+	}
 }
 
 export default function compile(source: string, options: CompileOptions = {}) {

src/compiler/interfaces.ts

@@ -121,6 +121,7 @@ export interface CompileOptions {
 	customElement?: boolean;
 	tag?: string;
 	css?: boolean;
+	loopGuardTimeout?: number;
 
 	preserveComments?: boolean;
 	preserveWhitespace?: boolean;

src/runtime/internal/dev.ts

@@ -96,10 +96,10 @@ export class SvelteComponentDev extends SvelteComponent {
 	}
 }
 
-export function loop_guard() {
+export function loop_guard(timeout) {
 	const start = Date.now();
 	return () => {
-		if (Date.now() - start > 100) {
+		if (Date.now() - start > timeout) {
 			throw new Error(`Infinite loop detected`);
 		}
 	};

test/js/samples/loop-protect/_config.js

@@ -1,5 +1,6 @@
 export default {
 	options: {
-		dev: true
-	}
-};
+		dev: true,
+		loopGuardTimeout: 100,
+	},
+};

test/js/samples/loop-protect/expected.js

@@ -35,28 +35,28 @@ function create_fragment(ctx) {
 }
 
 function instance($$self) {
-	const guard = loop_guard();
+	const guard = loop_guard(100);
 
 	while (true) {
 		foo();
 		guard();
 	}
 
-	const guard_1 = loop_guard();
+	const guard_1 = loop_guard(100);
 
 	for (; ; ) {
 		foo();
 		guard_1();
 	}
 
-	const guard_2 = loop_guard();
+	const guard_2 = loop_guard(100);
 
 	while (true) {
 		foo();
 		guard_2();
 	}
 
-	const guard_4 = loop_guard();
+	const guard_4 = loop_guard(100);
 
 	do {
 		foo();
@@ -68,11 +68,11 @@ function instance($$self) {
 	};
 
 	$$self.$inject_state = $$props => {
-
+		
 	};
 
 	$: {
-		const guard_3 = loop_guard();
+		const guard_3 = loop_guard(100);
 
 		while (true) {
 			foo();
@@ -81,7 +81,7 @@ function instance($$self) {
 	}
 
 	$: {
-		const guard_5 = loop_guard();
+		const guard_5 = loop_guard(100);
 
 		do {
 			foo();

test/runtime/samples/loop-protect/_config.js

@@ -2,5 +2,6 @@ export default {
 	error: 'Infinite loop detected',
 	compileOptions: {
 		dev: true,
+		loopGuardTimeout: 100,
 	}
 };