fix: refine css :global() selector checks in a compound selector

Author: tanhauhau

.changeset/dry-fans-march.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: refine css `:global()` selector checks in a compound selector

packages/svelte/src/compiler/errors.js

@@ -108,6 +108,8 @@ const css = {
 	'invalid-css-global-selector': () => `:global(...) must contain exactly one selector`,
 	'invalid-css-global-selector-list': () =>
 		`:global(...) must not contain type or universal selectors when used in a compound selector`,
+	'invalid-css-type-selector-placement': () =>
+		`:global(...) must not be followed with a type selector`,
 	'invalid-css-selector': () => `Invalid selector`,
 	'invalid-css-identifier': () => 'Expected a valid CSS identifier',
 	'invalid-nesting-selector': () => `Nesting selectors can only be used inside a rule`,

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

@@ -99,41 +99,31 @@ const validation_visitors = {
 			}
 		}
 
-		// ensure `:global(...)`contains a single selector
-		// (standalone :global() with multiple selectors is OK)
-		if (node.children.length > 1 || node.children[0].selectors.length > 1) {
-			for (const relative_selector of node.children) {
-				for (const selector of relative_selector.selectors) {
-					if (
-						selector.type === 'PseudoClassSelector' &&
-						selector.name === 'global' &&
-						selector.args !== null &&
-						selector.args.children.length > 1
-					) {
-						error(selector, 'invalid-css-global-selector');
-					}
-				}
-			}
-		}
-
-		// ensure `:global(...)` is not part of a larger compound selector
+		// ensure `:global(...)` do not lead to invalid css after `:global()` is removed
 		for (const relative_selector of node.children) {
 			for (let i = 0; i < relative_selector.selectors.length; i++) {
 				const selector = relative_selector.selectors[i];
 
 				if (selector.type === 'PseudoClassSelector' && selector.name === 'global') {
 					const child = selector.args?.children[0].children[0];
+					// ensure `:global(element)` to be at the first position in a compound selector
+					if (child?.selectors[0].type === 'TypeSelector' && i !== 0) {
+						error(selector, 'invalid-css-global-selector-list');
+					}
+
+					// ensure `:global(.class)` is not followed by a type selector, eg: `:global(.class)element`
+					if (relative_selector.selectors[i + 1]?.type === 'TypeSelector') {
+						error(relative_selector.selectors[i + 1], 'invalid-css-type-selector-placement');
+					}
+
+					// ensure `:global(...)`contains a single selector
+					// (standalone :global() with multiple selectors is OK)
 					if (
-						child?.selectors[0].type === 'TypeSelector' &&
-						!/[.:#]/.test(child.selectors[0].name[0]) &&
-						(i !== 0 ||
-							relative_selector.selectors
-								.slice(1)
-								.some(
-									(s) => s.type !== 'PseudoElementSelector' && s.type !== 'PseudoClassSelector'
-								))
+						selector.args !== null &&
+						selector.args.children.length > 1 &&
+						(node.children.length > 1 || relative_selector.selectors.length > 1)
 					) {
-						error(selector, 'invalid-css-global-selector-list');
+						error(selector, 'invalid-css-global-selector');
 					}
 				}
 			}

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

@@ -230,7 +230,7 @@ const visitors = {
 
 				context.state.specificity.bumped = true;
 
-				// TODO err... can this happen?
+				// for any :global() at the middle of compound selector
 				for (const selector of relative_selector.selectors) {
 					if (selector.type === 'PseudoClassSelector' && selector.name === 'global') {
 						remove_global_pseudo_class(selector);

packages/svelte/tests/validator/samples/css-invalid-global-selector-list/errors.json

@@ -0,0 +1,14 @@
+[
+	{
+		"code": "invalid-css-global-selector-list",
+		"message": ":global(...) must not contain type or universal selectors when used in a compound selector",
+		"start": {
+			"line": 20,
+			"column": 6
+		},
+		"end": {
+			"line": 20,
+			"column": 17
+		}
+	}
+]

packages/svelte/tests/validator/samples/css-invalid-global-selector-list/input.svelte

@@ -0,0 +1,27 @@
+<style>
+	::foo:global([data-state='checked']) {
+		color: red;
+	}
+	::foo:global(.foo) {
+		color: red;
+	}
+	::foo:global(#foo) {
+		color: red;
+	}
+	::foo:global(::foo) {
+		color: red;
+	}
+	::foo:global(:foo) {
+		color: red;
+	}
+	:global(h1) {
+		color: red;
+	}
+	::foo:global(h1) {
+		color: red;
+	}
+</style>
+
+<div>
+	<h1>hello world</h1>
+</div>

packages/svelte/tests/validator/samples/css-invalid-type-selector-placement/errors.json

@@ -0,0 +1,14 @@
+[
+	{
+		"code": "invalid-css-type-selector-placement",
+		"message": ":global(...) must not be followed with a type selector",
+		"start": {
+			"line": 17,
+			"column": 14
+		},
+		"end": {
+			"line": 17,
+			"column": 16
+		}
+	}
+]

packages/svelte/tests/validator/samples/css-invalid-type-selector-placement/input.svelte

@@ -0,0 +1,24 @@
+<style>
+	:global(.foo):foo {
+		color: red;
+	}
+	:global(.foo)::foo {
+		color: red;
+	}
+	:global(.foo).bar {
+		color: red;
+	}
+	:global(.foo)#baz {
+		color: red;
+	}
+	:global(.foo)[id] {
+		color: red;
+	}
+	:global(.foo)h1 {
+		color: red;
+	}
+</style>
+
+<div>
+	<h1 class="bar" id="baz">hello world</h1>
+</div>