chore: markdown runtime errors/warnings (#11304)

* chore: markdown runtime warnings

* on second thoughts

* start adding errors too

* lint

* centralise

Author: Rich-Harris

.prettierignore

@@ -5,6 +5,9 @@ packages/**/config/*.js
 packages/svelte/messages/**/*.md
 packages/svelte/src/compiler/errors.js
 packages/svelte/src/compiler/warnings.js
+packages/svelte/src/internal/client/errors.js
+packages/svelte/src/internal/client/warnings.js
+packages/svelte/src/internal/shared/warnings.js
 packages/svelte/tests/**/*.svelte
 packages/svelte/tests/**/_expected*
 packages/svelte/tests/**/_actual*

eslint.config.js

@@ -35,6 +35,9 @@ export default [
 			'**/tests',
 			'packages/svelte/scripts/process-messages/templates/*.js',
 			'packages/svelte/src/compiler/errors.js',
+			'packages/svelte/src/internal/client/errors.js',
+			'packages/svelte/src/internal/client/warnings.js',
+			'packages/svelte/src/internal/shared/warnings.js',
 			'packages/svelte/compiler/index.js',
 			// documentation can contain invalid examples
 			'documentation',

packages/svelte/messages/client-errors/effects.md

@@ -0,0 +1,3 @@
+## effect_update_depth_exceeded
+
+Maximum update depth exceeded. This can happen when a reactive block or effect repeatedly sets a new value. Svelte limits the number of nested updates to prevent infinite loops

packages/svelte/messages/client-errors/lifecycle.md

@@ -0,0 +1,7 @@
+## lifecycle_outside_component
+
+`%name%(...)` can only be used during component initialisation
+
+## lifecycle_legacy_only
+
+`%name%(...)` cannot be used in runes mode

packages/svelte/messages/client-warnings/warnings.md

@@ -0,0 +1,7 @@
+## lifecycle_double_unmount
+
+Tried to unmount a component that was not mounted
+
+## ownership_invalid_binding
+
+%parent% passed a value to %child% with `bind:`, but the value is owned by %owner%. Consider creating a binding between %owner% and %parent%

packages/svelte/messages/shared-warnings/warnings.md

@@ -0,0 +1,3 @@
+## dynamic_void_element_content
+
+`<svelte:element this="%tag%">` is a void element — it cannot have content

packages/svelte/scripts/process-messages/index.js

@@ -220,3 +220,7 @@ function transform(name, dest) {
 
 transform('compile-errors', 'src/compiler/errors.js');
 transform('compile-warnings', 'src/compiler/warnings.js');
+
+transform('client-warnings', 'src/internal/client/warnings.js');
+transform('client-errors', 'src/internal/client/errors.js');
+transform('shared-warnings', 'src/internal/shared/warnings.js');

packages/svelte/scripts/process-messages/templates/client-errors.js

@@ -0,0 +1,17 @@
+import { DEV } from 'esm-env';
+
+/**
+ * MESSAGE
+ * @param {string} PARAMETER
+ * @returns {never}
+ */
+export function CODE(PARAMETER) {
+	if (DEV) {
+		const error = new Error(`${'CODE'}\n${MESSAGE}`);
+		error.name = 'Svelte error';
+		throw error;
+	} else {
+		// TODO print a link to the documentation
+		throw new Error('CODE');
+	}
+}

packages/svelte/scripts/process-messages/templates/client-warnings.js

@@ -0,0 +1,17 @@
+import { DEV } from 'esm-env';
+
+var bold = 'font-weight: bold';
+var normal = 'font-weight: normal';
+
+/**
+ * MESSAGE
+ * @param {string} PARAMETER
+ */
+export function CODE(PARAMETER) {
+	if (DEV) {
+		console.warn(`%c[svelte] ${'CODE'}\n%c${MESSAGE}`, bold, normal);
+	} else {
+		// TODO print a link to the documentation
+		console.warn('CODE');
+	}
+}

packages/svelte/scripts/process-messages/templates/shared-warnings.js

@@ -0,0 +1,19 @@
+import { DEV } from 'esm-env';
+
+var bold = 'font-weight: bold';
+var normal = 'font-weight: normal';
+
+/**
+ * MESSAGE
+ * @param {boolean} trace
+ * @param {string} PARAMETER
+ */
+export function CODE(trace, PARAMETER) {
+	if (DEV) {
+		console.warn(`%c[svelte] ${'CODE'}\n%c${MESSAGE}`, bold, normal);
+		if (trace) console.trace('stack trace');
+	} else {
+		// TODO print a link to the documentation
+		console.warn('CODE');
+	}
+}

packages/svelte/src/index-client.js

@@ -1,6 +1,7 @@
 import { current_component_context, flush_sync, untrack } from './internal/client/runtime.js';
 import { is_array } from './internal/client/utils.js';
 import { user_effect } from './internal/client/index.js';
+import * as e from './internal/client/errors.js';
 
 /**
  * The `onMount` function schedules a callback to run as soon as the component has been mounted to the DOM.
@@ -18,7 +19,7 @@ import { user_effect } from './internal/client/index.js';
  */
 export function onMount(fn) {
 	if (current_component_context === null) {
-		throw new Error('onMount can only be used during component initialisation.');
+		e.lifecycle_outside_component('onMount');
 	}
 
 	if (current_component_context.l !== null) {
@@ -43,7 +44,7 @@ export function onMount(fn) {
  */
 export function onDestroy(fn) {
 	if (current_component_context === null) {
-		throw new Error('onDestroy can only be used during component initialisation.');
+		e.lifecycle_outside_component('onDestroy');
 	}
 
 	onMount(() => () => untrack(fn));
@@ -87,7 +88,7 @@ function create_custom_event(type, detail, { bubbles = false, cancelable = false
 export function createEventDispatcher() {
 	const component_context = current_component_context;
 	if (component_context === null) {
-		throw new Error('createEventDispatcher can only be used during component initialisation.');
+		e.lifecycle_outside_component('createEventDispatcher');
 	}
 
 	return (type, detail, options) => {
@@ -126,7 +127,7 @@ export function createEventDispatcher() {
  */
 export function beforeUpdate(fn) {
 	if (current_component_context === null) {
-		throw new Error('beforeUpdate can only be used during component initialisation');
+		e.lifecycle_outside_component('beforeUpdate');
 	}
 
 	if (current_component_context.l === null) {
@@ -150,11 +151,11 @@ export function beforeUpdate(fn) {
  */
 export function afterUpdate(fn) {
 	if (current_component_context === null) {
-		throw new Error('afterUpdate can only be used during component initialisation.');
+		e.lifecycle_outside_component('afterUpdate');
 	}
 
 	if (current_component_context.l === null) {
-		throw new Error('afterUpdate cannot be used in runes mode');
+		e.lifecycle_legacy_only('afterUpdate');
 	}
 
 	init_update_callbacks(current_component_context).a.push(fn);

packages/svelte/src/internal/client/dev/ownership.js

@@ -4,6 +4,7 @@ import { STATE_SYMBOL } from '../constants.js';
 import { render_effect } from '../reactivity/effects.js';
 import { current_component_context, untrack } from '../runtime.js';
 import { get_prototype_of } from '../utils.js';
+import * as w from '../warnings.js';
 
 /** @type {Record<string, Array<{ start: Location, end: Location, component: Function }>>} */
 const boundaries = {};
@@ -115,10 +116,7 @@ export function add_owner(object, owner, global = false) {
 			let original = get_owner(metadata);
 
 			if (owner.filename !== component.filename) {
-				let message = `${component.filename} passed a value to ${owner.filename} with \`bind:\`, but the value is owned by ${original.filename}. Consider creating a binding between ${original.filename} and ${component.filename}`;
-
-				// eslint-disable-next-line no-console
-				console.warn(message);
+				w.ownership_invalid_binding(component.filename, owner.filename, original.filename);
 			}
 		}
 	}
@@ -234,6 +232,7 @@ export function check_ownership(metadata) {
 					`${component.filename} mutated a value owned by ${original.filename}. This is strongly discouraged`
 				: 'Mutating a value outside the component that created it is strongly discouraged';
 
+		// TODO get rid of this, but implement message overloads first
 		// eslint-disable-next-line no-console
 		console.warn(
 			`${message}. Consider passing values to child components with \`bind:\`, or use a callback instead.`

packages/svelte/src/internal/client/errors.js

@@ -0,0 +1,53 @@
+/* This file is generated by scripts/process-messages.js. Do not edit! */
+
+import { DEV } from 'esm-env';
+
+/**
+ * Maximum update depth exceeded. This can happen when a reactive block or effect repeatedly sets a new value. Svelte limits the number of nested updates to prevent infinite loops
+ * @returns {never}
+ */
+export function effect_update_depth_exceeded() {
+	if (DEV) {
+		const error = new Error(`${"effect_update_depth_exceeded"}\n${"Maximum update depth exceeded. This can happen when a reactive block or effect repeatedly sets a new value. Svelte limits the number of nested updates to prevent infinite loops"}`);
+
+		error.name = 'Svelte error';
+		throw error;
+	} else {
+		// TODO print a link to the documentation
+		throw new Error("effect_update_depth_exceeded");
+	}
+}
+
+/**
+ * `%name%(...)` can only be used during component initialisation
+ * @param {string} name
+ * @returns {never}
+ */
+export function lifecycle_outside_component(name) {
+	if (DEV) {
+		const error = new Error(`${"lifecycle_outside_component"}\n${`\`${name}(...)\` can only be used during component initialisation`}`);
+
+		error.name = 'Svelte error';
+		throw error;
+	} else {
+		// TODO print a link to the documentation
+		throw new Error("lifecycle_outside_component");
+	}
+}
+
+/**
+ * `%name%(...)` cannot be used in runes mode
+ * @param {string} name
+ * @returns {never}
+ */
+export function lifecycle_legacy_only(name) {
+	if (DEV) {
+		const error = new Error(`${"lifecycle_legacy_only"}\n${`\`${name}(...)\` cannot be used in runes mode`}`);
+
+		error.name = 'Svelte error';
+		throw error;
+	} else {
+		// TODO print a link to the documentation
+		throw new Error("lifecycle_legacy_only");
+	}
+}

packages/svelte/src/internal/client/render.js

@@ -19,6 +19,7 @@ import {
 import { array_from } from './utils.js';
 import { handle_event_propagation } from './dom/elements/events.js';
 import { reset_head_anchor } from './dom/blocks/svelte-head.js';
+import * as w from './warnings.js';
 
 /** @type {Set<string>} */
 export const all_registered_events = new Set();
@@ -269,6 +270,7 @@ function _mount(Component, { target, anchor, props = {}, events, context, intro
 				target.removeEventListener(event_name, bound_event_listener);
 			}
 			root_event_handles.delete(event_handle);
+			mounted_components.delete(component);
 		};
 	});
 
@@ -289,8 +291,9 @@ let mounted_components = new WeakMap();
 export function unmount(component) {
 	const fn = mounted_components.get(component);
 	if (DEV && !fn) {
+		w.lifecycle_double_unmount();
 		// eslint-disable-next-line no-console
-		console.warn('Tried to unmount a component that was not mounted.');
+		console.trace('stack trace');
 	}
 	fn?.();
 }

packages/svelte/src/internal/client/runtime.js

@@ -22,6 +22,7 @@ import { add_owner } from './dev/ownership.js';
 import { mutate, set, source } from './reactivity/sources.js';
 import { update_derived } from './reactivity/deriveds.js';
 import { inspect_captured_signals, inspect_fn, set_inspect_fn } from './dev/inspect.js';
+import * as e from './errors.js';
 
 const FLUSH_MICROTASK = 0;
 const FLUSH_SYNC = 1;
@@ -412,13 +413,7 @@ export function execute_effect(effect) {
 function infinite_loop_guard() {
 	if (flush_count > 1000) {
 		flush_count = 0;
-		throw new Error(
-			'ERR_SVELTE_TOO_MANY_UPDATES' +
-				(DEV
-					? ': Maximum update depth exceeded. This can happen when a reactive block or effect ' +
-						'repeatedly sets a new value. Svelte limits the number of nested updates to prevent infinite loops.'
-					: '')
-		);
+		e.effect_update_depth_exceeded();
 	}
 	flush_count++;
 }
@@ -880,12 +875,12 @@ export function is_signal(val) {
  * @returns {T}
  */
 export function getContext(key) {
-	const context_map = get_or_init_context_map();
+	const context_map = get_or_init_context_map('getContext');
 	const result = /** @type {T} */ (context_map.get(key));
 
 	if (DEV) {
 		// @ts-expect-error
-		const fn = current_component_context?.function;
+		const fn = current_component_context.function;
 		if (fn) {
 			add_owner(result, fn, true);
 		}
@@ -908,7 +903,7 @@ export function getContext(key) {
  * @returns {T}
  */
 export function setContext(key, context) {
-	const context_map = get_or_init_context_map();
+	const context_map = get_or_init_context_map('setContext');
 	context_map.set(key, context);
 	return context;
 }
@@ -922,7 +917,7 @@ export function setContext(key, context) {
  * @returns {boolean}
  */
 export function hasContext(key) {
-	const context_map = get_or_init_context_map();
+	const context_map = get_or_init_context_map('hasContext');
 	return context_map.has(key);
 }
 
@@ -936,7 +931,7 @@ export function hasContext(key) {
  * @returns {T}
  */
 export function getAllContexts() {
-	const context_map = get_or_init_context_map();
+	const context_map = get_or_init_context_map('getAllContexts');
 
 	if (DEV) {
 		// @ts-expect-error
@@ -951,16 +946,18 @@ export function getAllContexts() {
 	return /** @type {T} */ (context_map);
 }
 
-/** @returns {Map<unknown, unknown>} */
-function get_or_init_context_map() {
-	const component_context = current_component_context;
-	if (component_context === null) {
-		throw new Error(
-			'ERR_SVELTE_ORPHAN_CONTEXT' +
-				(DEV ? 'Context can only be used during component initialisation.' : '')
-		);
+/**
+ * @param {string} name
+ * @returns {Map<unknown, unknown>}
+ */
+function get_or_init_context_map(name) {
+	if (current_component_context === null) {
+		e.lifecycle_outside_component(name);
 	}
-	return (component_context.c ??= new Map(get_parent_context(component_context) || undefined));
+
+	return (current_component_context.c ??= new Map(
+		get_parent_context(current_component_context) || undefined
+	));
 }
 
 /**