feat: add css.hasGlobal to compile output (#15450)

* feat: add `hasUnscopedGlobalCss` to `compile` metadata

* chore: rename to `has_unscoped_global`

* fix: handle `-global` keyframes

* chore: guard the check if the value is already true

* update types

* add tests

* tweak

* tweak

* regenerate types

* Update .changeset/plenty-hotels-mix.md

* fix test, add failing test

* fix

* fix

* fix jsdoc

* unused

* fix

* lint

* rename

* rename

* reduce indirection

* tidy up

* revert

* tweak

* lint

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

Author: paoloricciuti

.changeset/plenty-hotels-mix.md

@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: add `css.hasGlobal` to `compile` output

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

@@ -118,6 +118,7 @@ function read_rule(parser) {
 		metadata: {
 			parent_rule: null,
 			has_local_selectors: false,
+			has_global_selectors: false,
 			is_global_block: false
 		}
 	};
@@ -342,6 +343,7 @@ function read_selector(parser, inside_pseudo_class = false) {
 				children,
 				metadata: {
 					rule: null,
+					is_global: false,
 					used: false
 				}
 			};

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

@@ -7,13 +7,15 @@ import { is_keyframes_node } from '../../css.js';
 import { is_global, is_unscoped_pseudo_class } from './utils.js';
 
 /**
- * @typedef {Visitors<
- *   AST.CSS.Node,
- *   {
- *     keyframes: string[];
- *     rule: AST.CSS.Rule | null;
- *   }
- * >} CssVisitors
+ * @typedef {{
+ *   keyframes: string[];
+ *   rule: AST.CSS.Rule | null;
+ *   analysis: ComponentAnalysis;
+ * }} CssState
+ */
+
+/**
+ * @typedef {Visitors<AST.CSS.Node, CssState>} CssVisitors
  */
 
 /**
@@ -28,6 +30,15 @@ function is_global_block_selector(simple_selector) {
 	);
 }
 
+/**
+ * @param {AST.SvelteNode[]} path
+ */
+function is_unscoped(path) {
+	return path
+		.filter((node) => node.type === 'Rule')
+		.every((node) => node.metadata.has_global_selectors);
+}
+
 /**
  *
  * @param {Array<AST.CSS.Node>} path
@@ -42,6 +53,9 @@ const css_visitors = {
 		if (is_keyframes_node(node)) {
 			if (!node.prelude.startsWith('-global-') && !is_in_global_block(context.path)) {
 				context.state.keyframes.push(node.prelude);
+			} else if (node.prelude.startsWith('-global-')) {
+				// we don't check if the block.children.length because the keyframe is still added even if empty
+				context.state.analysis.css.has_global ||= is_unscoped(context.path);
 			}
 		}
 
@@ -99,10 +113,12 @@ const css_visitors = {
 
 		node.metadata.rule = context.state.rule;
 
-		node.metadata.used ||= node.children.every(
+		node.metadata.is_global = node.children.every(
 			({ metadata }) => metadata.is_global || metadata.is_global_like
 		);
 
+		node.metadata.used ||= node.metadata.is_global;
+
 		if (
 			node.metadata.rule?.metadata.parent_rule &&
 			node.children[0]?.selectors[0]?.type === 'NestingSelector'
@@ -190,6 +206,7 @@ const css_visitors = {
 
 				if (idx !== -1) {
 					is_global_block = true;
+
 					for (let i = idx + 1; i < child.selectors.length; i++) {
 						walk(/** @type {AST.CSS.Node} */ (child.selectors[i]), null, {
 							ComplexSelector(node) {
@@ -242,16 +259,26 @@ const css_visitors = {
 			}
 		}
 
-		context.next({
-			...context.state,
-			rule: node
-		});
+		const state = { ...context.state, rule: node };
 
-		node.metadata.has_local_selectors = node.prelude.children.some((selector) => {
-			return selector.children.some(
-				({ metadata }) => !metadata.is_global && !metadata.is_global_like
-			);
-		});
+		// visit selector list first, to populate child selector metadata
+		context.visit(node.prelude, state);
+
+		for (const selector of node.prelude.children) {
+			node.metadata.has_global_selectors ||= selector.metadata.is_global;
+			node.metadata.has_local_selectors ||= !selector.metadata.is_global;
+		}
+
+		// if this rule has a ComplexSelector whose RelativeSelector children are all
+		// `:global(...)`, and the rule contains declarations (rather than just
+		// nested rules) then the component as a whole includes global CSS
+		context.state.analysis.css.has_global ||=
+			node.metadata.has_global_selectors &&
+			node.block.children.filter((child) => child.type === 'Declaration').length > 0 &&
+			is_unscoped(context.path);
+
+		// visit block list, so parent rule metadata is populated
+		context.visit(node.block, state);
 	},
 	NestingSelector(node, context) {
 		const rule = /** @type {AST.CSS.Rule} */ (context.state.rule);
@@ -289,5 +316,12 @@ const css_visitors = {
  * @param {ComponentAnalysis} analysis
  */
 export function analyze_css(stylesheet, analysis) {
-	walk(stylesheet, { keyframes: analysis.css.keyframes, rule: null }, css_visitors);
+	/** @type {CssState} */
+	const css_state = {
+		keyframes: analysis.css.keyframes,
+		rule: null,
+		analysis
+	};
+
+	walk(stylesheet, css_state, css_visitors);
 }

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

@@ -456,7 +456,8 @@ export function analyze_component(root, source, options) {
 						hash
 					})
 				: '',
-			keyframes: []
+			keyframes: [],
+			has_global: false
 		},
 		source,
 		undefined_exports: new Map(),

packages/svelte/src/compiler/phases/3-transform/css/index.js

@@ -59,7 +59,8 @@ export function render_stylesheet(source, analysis, options) {
 			// generateMap takes care of calculating source relative to file
 			source: options.filename,
 			file: options.cssOutputFilename || options.filename
-		})
+		}),
+		hasGlobal: analysis.css.has_global
 	};
 
 	merge_with_preprocessor_map(css, options, css.map.sources[0]);

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

@@ -74,6 +74,7 @@ export interface ComponentAnalysis extends Analysis {
 		ast: AST.CSS.StyleSheet | null;
 		hash: string;
 		keyframes: string[];
+		has_global: boolean;
 	};
 	source: string;
 	undefined_exports: Map<string, Node>;

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

@@ -34,6 +34,10 @@ export namespace _CSS {
 		metadata: {
 			parent_rule: null | Rule;
 			has_local_selectors: boolean;
+			/**
+			 * `true` if the rule contains a ComplexSelector whose RelativeSelectors are all global or global-like
+			 */
+			has_global_selectors: boolean;
 			/**
 			 * `true` if the rule contains a `:global` selector, and therefore everything inside should be unscoped
 			 */
@@ -64,6 +68,7 @@ export namespace _CSS {
 		/** @internal */
 		metadata: {
 			rule: null | Rule;
+			is_global: boolean;
 			/** True if this selector applies to an element. For global selectors, this is defined in css-analyze, for others in css-prune while scoping */
 			used: boolean;
 		};

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

@@ -18,6 +18,8 @@ export interface CompileResult {
 		code: string;
 		/** A source map */
 		map: SourceMap;
+		/** Whether or not the CSS includes global rules */
+		hasGlobal: boolean;
 	};
 	/**
 	 * An array of warning objects that were generated during compilation. Each warning has several properties:

packages/svelte/tests/css/samples/global-keyframes/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	hasGlobal: true
+});

packages/svelte/tests/css/samples/global-local-nested/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	hasGlobal: false
+});