breaking: deprecate context="module" in favor of module

Also reserve a few attributes, which we may or may not use in the future

closes #12637

Author: dummdidumm

.changeset/quick-eagles-sit.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+breaking: deprecate `context="module"` in favor of `module`

documentation/docs/02-template-syntax/01-component-fundamentals.md

@@ -161,16 +161,16 @@ If you'd like to react to changes to a prop, use the `$derived` or `$effect` run
 
 For more information on reactivity, read the documentation around runes.
 
-## <script context="module">
+## <script module>
 
-A `<script>` tag with a `context="module"` attribute runs once when the module first evaluates, rather than for each component instance. Values declared in this block are accessible from a regular `<script>` (and the component markup) but not vice versa.
+A `<script>` tag with a `module` attribute runs once when the module first evaluates, rather than for each component instance. Values declared in this block are accessible from a regular `<script>` (and the component markup) but not vice versa.
 
 You can `export` bindings from this block, and they will become exports of the compiled module.
 
 You cannot `export default`, since the default export is the component itself.
 
 ```svelte
-<script context="module">
+<script module>
 	let totalComponents = 0;
 
 	// the export keyword allows this function to imported with e.g.

packages/svelte/messages/compile-errors/script.md

@@ -16,7 +16,7 @@
 
 ## declaration_duplicate_module_import
 
-> Cannot declare same variable name which is imported inside `<script context="module">`
+> Cannot declare same variable name which is imported inside `<script module>`
 
 ## derived_invalid_export
 
@@ -152,7 +152,7 @@
 
 ## store_invalid_subscription
 
-> Cannot reference store value inside `<script context="module">`
+> Cannot reference store value inside `<script module>`
 
 ## store_invalid_subscription_module
 

packages/svelte/messages/compile-errors/template.md

@@ -216,12 +216,20 @@ HTML restricts where certain elements can appear. In case of a violation the bro
 
 ## script_duplicate
 
-> A component can have a single top-level `<script>` element and/or a single top-level `<script context="module">` element
+> A component can have a single top-level `<script>` element and/or a single top-level `<script module>` element
+
+## script_invalid_attribute_value
+
+> If the %name% attribute is supplied, it must be a boolean attribute
 
 ## script_invalid_context
 
 > If the context attribute is supplied, its value must be "module"
 
+## script_reserved_attribute
+
+> The %name% attribute is reserved and cannot be used
+
 ## slot_attribute_duplicate
 
 > Duplicate slot name '%name%' in <%component%>

packages/svelte/messages/compile-warnings/template.md

@@ -50,6 +50,10 @@ HTML restricts where certain elements can appear. In case of a violation the bro
 
 This code will work when the component is rendered on the client (which is why this is a warning rather than an error), but if you use server rendering it will cause hydration to fail.
 
+## script_context_deprecated
+
+> `context="module"` is deprecated, use the `module` attribute instead
+
 ## slot_element_deprecated
 
 > Using `<slot>` to render parent content is deprecated. Use `{@render ...}` tags instead

packages/svelte/src/compiler/errors.js

@@ -99,12 +99,12 @@ export function declaration_duplicate(node, name) {
 }
 
 /**
- * Cannot declare same variable name which is imported inside `<script context="module">`
+ * Cannot declare same variable name which is imported inside `<script module>`
  * @param {null | number | NodeLike} node
  * @returns {never}
  */
 export function declaration_duplicate_module_import(node) {
-	e(node, "declaration_duplicate_module_import", "Cannot declare same variable name which is imported inside `<script context=\"module\">`");
+	e(node, "declaration_duplicate_module_import", "Cannot declare same variable name which is imported inside `<script module>`");
 }
 
 /**
@@ -417,12 +417,12 @@ export function store_invalid_scoped_subscription(node) {
 }
 
 /**
- * Cannot reference store value inside `<script context="module">`
+ * Cannot reference store value inside `<script module>`
  * @param {null | number | NodeLike} node
  * @returns {never}
  */
 export function store_invalid_subscription(node) {
-	e(node, "store_invalid_subscription", "Cannot reference store value inside `<script context=\"module\">`");
+	e(node, "store_invalid_subscription", "Cannot reference store value inside `<script module>`");
 }
 
 /**
@@ -1044,12 +1044,22 @@ export function render_tag_invalid_spread_argument(node) {
 }
 
 /**
- * A component can have a single top-level `<script>` element and/or a single top-level `<script context="module">` element
+ * A component can have a single top-level `<script>` element and/or a single top-level `<script module>` element
  * @param {null | number | NodeLike} node
  * @returns {never}
  */
 export function script_duplicate(node) {
-	e(node, "script_duplicate", "A component can have a single top-level `<script>` element and/or a single top-level `<script context=\"module\">` element");
+	e(node, "script_duplicate", "A component can have a single top-level `<script>` element and/or a single top-level `<script module>` element");
+}
+
+/**
+ * If the %name% attribute is supplied, it must be a boolean attribute
+ * @param {null | number | NodeLike} node
+ * @param {string} name
+ * @returns {never}
+ */
+export function script_invalid_attribute_value(node, name) {
+	e(node, "script_invalid_attribute_value", `If the ${name} attribute is supplied, it must be a boolean attribute`);
 }
 
 /**
@@ -1061,6 +1071,16 @@ export function script_invalid_context(node) {
 	e(node, "script_invalid_context", "If the context attribute is supplied, its value must be \"module\"");
 }
 
+/**
+ * The %name% attribute is reserved and cannot be used
+ * @param {null | number | NodeLike} node
+ * @param {string} name
+ * @returns {never}
+ */
+export function script_reserved_attribute(node, name) {
+	e(node, "script_reserved_attribute", `The ${name} attribute is reserved and cannot be used`);
+}
+
 /**
  * Duplicate slot name '%name%' in <%component%>
  * @param {null | number | NodeLike} node

packages/svelte/src/compiler/migrate/index.js

@@ -1,5 +1,4 @@
 /** @import { VariableDeclarator, Node, Identifier } from 'estree' */
-/** @import { SvelteNode } from '../types/template.js' */
 /** @import { Visitors } from 'zimmerframe' */
 /** @import { ComponentAnalysis } from '../phases/types.js' */
 /** @import { Scope } from '../phases/scope.js' */
@@ -58,6 +57,13 @@ export function migrate(source) {
 			needs_run: false
 		};
 
+		if (parsed.module) {
+			const context = parsed.module.attributes.find((attr) => attr.name === 'context');
+			if (context) {
+				state.str.update(context.start, context.end, 'module');
+			}
+		}
+
 		if (parsed.instance) {
 			walk(parsed.instance.content, state, instance_script);
 		}
@@ -223,7 +229,7 @@ export function migrate(source) {
  * }} State
  */
 
-/** @type {Visitors<SvelteNode, State>} */
+/** @type {Visitors<Compiler.SvelteNode, State>} */
 const instance_script = {
 	_(node, { state, next }) {
 		// @ts-expect-error
@@ -472,7 +478,7 @@ const instance_script = {
 	}
 };
 
-/** @type {Visitors<SvelteNode, State>} */
+/** @type {Visitors<Compiler.SvelteNode, State>} */
 const template = {
 	Identifier(node, { state, path }) {
 		handle_identifier(node, state, path);
@@ -590,7 +596,7 @@ const template = {
 /**
  * @param {VariableDeclarator} declarator
  * @param {MagicString} str
- * @param {Compiler.SvelteNode[]} path
+ * @param {Array<Compiler.SvelteNode>} path
  */
 function extract_type_and_comment(declarator, str, path) {
 	const parent = path.at(-1);

packages/svelte/src/compiler/phases/1-parse/read/script.js

@@ -4,6 +4,7 @@
 import * as acorn from '../acorn.js';
 import { regex_not_newline_characters } from '../../patterns.js';
 import * as e from '../../../errors.js';
+import * as w from '../../../warnings.js';
 
 const regex_closing_script_tag = /<\/script\s*>/;
 const regex_starts_with_closing_script_tag = /^<\/script\s*>/;
@@ -13,22 +14,42 @@ const regex_starts_with_closing_script_tag = /^<\/script\s*>/;
  * @returns {string}
  */
 function get_context(attributes) {
-	const context = attributes.find(
-		/** @param {any} attribute */ (attribute) => attribute.name === 'context'
-	);
-	if (!context) return 'default';
+	for (const attribute of attributes) {
+		switch (attribute.name) {
+			case 'context': {
+				if (attribute.value.length !== 1 || attribute.value[0].type !== 'Text') {
+					e.script_invalid_context(attribute.start);
+				}
 
-	if (context.value.length !== 1 || context.value[0].type !== 'Text') {
-		e.script_invalid_context(context.start);
-	}
+				const value = attribute.value[0].data;
+
+				if (value !== 'module') {
+					e.script_invalid_context(attribute.start);
+				}
+
+				w.script_context_deprecated(attribute);
 
-	const value = context.value[0].data;
+				return value;
+			}
+			case 'module': {
+				if (attribute.value !== true) {
+					// Deliberately a generic code to future-proof for potential other attributes
+					e.script_invalid_attribute_value(attribute.start, attribute.name);
+				}
 
-	if (value !== 'module') {
-		e.script_invalid_context(context.start);
+				return 'module';
+			}
+			case 'server':
+			case 'client':
+			case 'worker':
+			case 'test':
+			case 'default': {
+				e.script_reserved_attribute(attribute.start, attribute.name);
+			}
+		}
 	}
 
-	return value;
+	return 'default';
 }
 
 /**

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -330,7 +330,7 @@ export function analyze_component(root, source, options) {
 
 			if (module.ast) {
 				for (const { node, path } of references) {
-					// if the reference is inside context="module", error. this is a bit hacky but it works
+					// if the reference is inside module, error. this is a bit hacky but it works
 					if (
 						/** @type {number} */ (node.start) > /** @type {number} */ (module.ast.start) &&
 						/** @type {number} */ (node.end) < /** @type {number} */ (module.ast.end) &&

packages/svelte/src/compiler/types/template.d.ts

@@ -61,7 +61,7 @@ export interface Root extends BaseNode {
 	css: Css.StyleSheet | null;
 	/** The parsed `<script>` element, if exists */
 	instance: Script | null;
-	/** The parsed `<script context="module">` element, if exists */
+	/** The parsed `<script module>` element, if exists */
 	module: Script | null;
 	metadata: {
 		/** Whether the component was parsed with typescript */

packages/svelte/src/compiler/warnings.js

@@ -117,6 +117,7 @@ export const codes = [
 	"element_invalid_self_closing_tag",
 	"event_directive_deprecated",
 	"node_invalid_placement_ssr",
+	"script_context_deprecated",
 	"slot_element_deprecated",
 	"svelte_component_deprecated",
 	"svelte_element_invalid_this"
@@ -769,6 +770,14 @@ export function node_invalid_placement_ssr(node, thing, parent) {
 	w(node, "node_invalid_placement_ssr", `${thing} is invalid inside \`<${parent}>\`. When rendering this component on the server, the resulting HTML will be modified by the browser, likely resulting in a \`hydration_mismatch\` warning`);
 }
 
+/**
+ * `context="module"` is deprecated, use the `module` attribute instead
+ * @param {null | NodeLike} node
+ */
+export function script_context_deprecated(node) {
+	w(node, "script_context_deprecated", "`context=\"module\"` is deprecated, use the `module` attribute instead");
+}
+
 /**
  * Using `<slot>` to render parent content is deprecated. Use `{@render ...}` tags instead
  * @param {null | NodeLike} node

packages/svelte/tests/compiler-errors/samples/export-state-module/main.svelte

@@ -1,4 +1,4 @@
-<script context="module">
+<script module>
 	export const object = $state({
 		ok: true
 	});

packages/svelte/tests/compiler-errors/samples/runes-export-let/main.svelte

@@ -1,4 +1,4 @@
-<script context="module">
+<script module>
     export let bar = ''; // check that it doesn't error here already
 </script>
 

packages/svelte/tests/compiler-errors/samples/store-autosub-context-module/_config.js

@@ -3,7 +3,7 @@ import { test } from '../../test';
 export default test({
 	error: {
 		code: 'store_invalid_subscription',
-		message: 'Cannot reference store value inside `<script context="module">`',
+		message: 'Cannot reference store value inside `<script module>`',
 		position: [164, 168]
 	}
 });

packages/svelte/tests/compiler-errors/samples/store-autosub-context-module/main.svelte

@@ -1,4 +1,4 @@
-<script context="module">
+<script module>
 	// this should be fine (state rune is not treated as a store)
 	const state = $state(0);
 	// this is not

packages/svelte/tests/migrate/samples/script-context-module/input.svelte

@@ -0,0 +1,3 @@
+<script context="module">
+	let foo = true;
+</script>

packages/svelte/tests/migrate/samples/script-context-module/output.svelte

@@ -0,0 +1,3 @@
+<script module>
+	let foo = true;
+</script>

packages/svelte/tests/parser-modern/samples/options/input.svelte

@@ -1,6 +1,6 @@
 <svelte:options customElement="my-custom-element" runes={true} />
 
-<script context="module" lang="ts">
+<script module lang="ts">
 </script>
 
 <script lang="ts" generics="T extends { foo: number }">

packages/svelte/tests/runtime-legacy/samples/component-namespace/Widget.svelte

@@ -1,5 +1,5 @@
-<script context="module">
-  import Tooltip from './Tooltip.svelte';
+<script module>
+	import Tooltip from './Tooltip.svelte';
 
-  export const Widget = { Tooltip };
-</script>
+	export const Widget = { Tooltip };
+</script>

packages/svelte/tests/runtime-legacy/samples/component-namespaced/components.svelte

@@ -1,5 +1,5 @@
-<script context="module">
-  import Foo from './Foo.svelte';
+<script module>
+	import Foo from './Foo.svelte';
 
-  export const Components = { Foo };
-</script>
+	export const Components = { Foo };
+</script>