fix: make sure all string comparisons are case-insensitive

src/css-node.ts

@@ -45,7 +45,7 @@ import {
 	FLAG_HAS_PARENS,
 } from './arena'
 
-import { CHAR_MINUS_HYPHEN, CHAR_PLUS, is_whitespace } from './string-utils'
+import { CHAR_MINUS_HYPHEN, CHAR_PLUS, is_whitespace, str_starts_with } from './string-utils'
 import { parse_dimension } from './parse-utils'
 
 // Type name lookup table - maps numeric type to CSSTree-compatible strings
@@ -239,7 +239,7 @@ export class CSSNode {
 			// For URL nodes without children (e.g., @import url(...)), extract from text
 			// Handle both url("...") and url('...') and just "..." or '...'
 			const text = this.text
-			if (text.startsWith('url(')) {
+			if (str_starts_with(text, 'url(')) {
 				// url("...") or url('...') or url(...) - extract content between parens
 				const openParen = text.indexOf('(')
 				const closeParen = text.lastIndexOf(')')

src/parse-anplusb.ts

@@ -7,7 +7,7 @@
 import { Lexer } from './lexer'
 import { NTH_SELECTOR, CSSDataArena } from './arena'
 import { TOKEN_IDENT, TOKEN_NUMBER, TOKEN_DIMENSION, TOKEN_DELIM, type TokenType } from './token-types'
-import { CHAR_MINUS_HYPHEN, CHAR_PLUS } from './string-utils'
+import { CHAR_MINUS_HYPHEN, CHAR_PLUS, str_equals, str_index_of } from './string-utils'
 import { skip_whitespace_forward } from './parse-utils'
 import { CSSNode } from './css-node'
 
@@ -53,9 +53,9 @@ export class ANplusBParser {
 
 		// Handle special keywords: odd, even
 		if (this.lexer.token_type === TOKEN_IDENT) {
-			const text = this.source.substring(this.lexer.token_start, this.lexer.token_end).toLowerCase()
+			const text = this.source.substring(this.lexer.token_start, this.lexer.token_end)
 
-			if (text === 'odd' || text === 'even') {
+			if (str_equals('odd', text) || str_equals('even', text)) {
 				a_start = this.lexer.token_start
 				a_end = this.lexer.token_end
 				return this.create_anplusb_node(node_start, a_start, a_end, 0, 0)
@@ -168,7 +168,7 @@ export class ANplusBParser {
 		// Handle dimension tokens: 2n, 3n+1, -5n-2
 		if (this.lexer.token_type === TOKEN_DIMENSION) {
 			const token_text = this.source.substring(this.lexer.token_start, this.lexer.token_end)
-			const n_index = token_text.toLowerCase().indexOf('n')
+			const n_index = str_index_of(token_text, 'n')
 
 			if (n_index !== -1) {
 				a_start = this.lexer.token_start

src/parse-atrule-prelude.test.ts

@@ -1361,3 +1361,63 @@ describe('parse_atrule_prelude()', () => {
 		})
 	})
 })
+
+describe('Case-insensitive at-rule keywords', () => {
+	it('should parse @MEDIA with uppercase', () => {
+		const root = parse('@MEDIA (min-width: 768px) { body { color: red; } }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('MEDIA')
+	})
+
+	it('should parse @Media with mixed case', () => {
+		const root = parse('@Media (min-width: 768px) { body { color: red; } }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('Media')
+	})
+
+	it('should parse @IMPORT with uppercase', () => {
+		const root = parse('@IMPORT url("style.css");')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('IMPORT')
+	})
+
+	it('should parse @SUPPORTS with uppercase', () => {
+		const root = parse('@SUPPORTS (display: grid) { body { display: grid; } }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('SUPPORTS')
+	})
+
+	it('should parse @LAYER with uppercase', () => {
+		const root = parse('@LAYER base { }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('LAYER')
+	})
+
+	it('should parse @CONTAINER with uppercase', () => {
+		const root = parse('@CONTAINER (min-width: 400px) { }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('CONTAINER')
+	})
+
+	it('should parse media query operators in uppercase', () => {
+		const root = parse('@media (min-width: 768px) AND (max-width: 1024px) { }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('media')
+		// Verify the prelude was parsed (operators are case-insensitive)
+		expect(atrule?.children.length).toBeGreaterThan(0)
+	})
+
+	it('should parse OR operator in uppercase', () => {
+		const root = parse('@supports (display: grid) OR (display: flex) { }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('supports')
+		expect(atrule?.children.length).toBeGreaterThan(0)
+	})
+
+	it('should parse NOT operator in uppercase', () => {
+		const root = parse('@supports NOT (display: grid) { }')
+		const atrule = root.first_child
+		expect(atrule?.name).toBe('supports')
+		expect(atrule?.children.length).toBeGreaterThan(0)
+	})
+})

src/parse-selector.ts

@@ -47,6 +47,7 @@ import { skip_whitespace_forward, skip_whitespace_and_comments_forward, skip_whi
 import {
 	is_whitespace,
 	is_vendor_prefixed,
+	str_equals,
 	CHAR_PLUS,
 	CHAR_TILDE,
 	CHAR_GREATER_THAN,
@@ -751,16 +752,16 @@ export class SelectorParser {
 		// Parse the content inside the parentheses
 		if (content_end > content_start) {
 			// Check if this is an nth-* pseudo-class
-			let func_name = this.source.substring(func_name_start, func_name_end).toLowerCase()
+			let func_name_substr = this.source.substring(func_name_start, func_name_end)
 
-			if (this.is_nth_pseudo(func_name)) {
+			if (this.is_nth_pseudo(func_name_substr)) {
 				// Parse as An+B expression
 				let child = this.parse_nth_expression(content_start, content_end)
 				if (child !== null) {
 					this.arena.set_first_child(node, child)
 					this.arena.set_last_child(node, child)
 				}
-			} else if (func_name === 'lang') {
+			} else if (str_equals('lang', func_name_substr)) {
 				// Parse as :lang() - comma-separated language identifiers
 				this.parse_lang_identifiers(content_start, content_end, node)
 			} else {
@@ -771,7 +772,7 @@ export class SelectorParser {
 
 				// Recursively parse the content as a selector
 				// Only :has() accepts relative selectors (starting with combinator)
-				let allow_relative = func_name === 'has'
+				let allow_relative = str_equals('has', func_name_substr)
 				let child_selector = this.parse_selector(content_start, content_end, this.lexer.line, this.lexer.column, allow_relative)
 
 				// Restore lexer state and selector_end
@@ -792,12 +793,12 @@ export class SelectorParser {
 	// Check if pseudo-class name is an nth-* pseudo
 	private is_nth_pseudo(name: string): boolean {
 		return (
-			name === 'nth-child' ||
-			name === 'nth-last-child' ||
-			name === 'nth-of-type' ||
-			name === 'nth-last-of-type' ||
-			name === 'nth-col' ||
-			name === 'nth-last-col'
+			str_equals('nth-child', name) ||
+			str_equals('nth-last-child', name) ||
+			str_equals('nth-of-type', name) ||
+			str_equals('nth-last-of-type', name) ||
+			str_equals('nth-col', name) ||
+			str_equals('nth-last-col', name)
 		)
 	}
 

src/parse-value.test.ts

@@ -659,4 +659,62 @@ describe('Value Node Types', () => {
 			})
 		})
 	})
+
+	describe('Case-insensitive function names', () => {
+		const getValue = (css: string) => {
+			const root = parse(css)
+			const rule = root.first_child
+			const decl = rule?.first_child?.next_sibling?.first_child
+			return decl?.values[0]
+		}
+
+		it('should parse URL() with uppercase', () => {
+			const value = getValue('div { background: URL("image.png"); }')
+			expect(value?.type).toBe(URL)
+			expect(value?.text).toBe('URL("image.png")')
+		})
+
+		it('should parse Url() with mixed case', () => {
+			const value = getValue('div { background: Url("image.png"); }')
+			expect(value?.type).toBe(URL)
+			expect(value?.text).toBe('Url("image.png")')
+		})
+
+		it('should parse CALC() with uppercase', () => {
+			const value = getValue('div { width: CALC(100% - 20px); }')
+			expect(value?.type).toBe(FUNCTION)
+			expect(value?.text).toBe('CALC(100% - 20px)')
+		})
+
+		it('should parse Calc() with mixed case', () => {
+			const value = getValue('div { width: Calc(100% - 20px); }')
+			expect(value?.type).toBe(FUNCTION)
+			expect(value?.text).toBe('Calc(100% - 20px)')
+		})
+
+		it('should parse RGB() with uppercase', () => {
+			const value = getValue('div { color: RGB(255, 0, 0); }')
+			expect(value?.type).toBe(FUNCTION)
+			expect(value?.text).toBe('RGB(255, 0, 0)')
+		})
+
+		it('should parse RGBA() with uppercase', () => {
+			const value = getValue('div { color: RGBA(255, 0, 0, 0.5); }')
+			expect(value?.type).toBe(FUNCTION)
+			expect(value?.text).toBe('RGBA(255, 0, 0, 0.5)')
+		})
+
+		it('should parse unquoted URL() with uppercase', () => {
+			const value = getValue('div { background: URL(image.png); }')
+			expect(value?.type).toBe(URL)
+			expect(value?.text).toBe('URL(image.png)')
+			expect(value?.value).toBe('image.png')
+		})
+
+		it('should handle nested functions with uppercase', () => {
+			const value = getValue('div { width: CALC(MAX(100%, 50px) - 20px); }')
+			expect(value?.type).toBe(FUNCTION)
+			expect(value?.children[0].type).toBe(FUNCTION)
+		})
+	})
 })

src/parse-value.ts

@@ -15,7 +15,7 @@ import {
 	TOKEN_LEFT_PAREN,
 	TOKEN_RIGHT_PAREN,
 } from './token-types'
-import { is_whitespace, CHAR_MINUS_HYPHEN, CHAR_PLUS, CHAR_ASTERISK, CHAR_FORWARD_SLASH } from './string-utils'
+import { is_whitespace, CHAR_MINUS_HYPHEN, CHAR_PLUS, CHAR_ASTERISK, CHAR_FORWARD_SLASH, str_equals } from './string-utils'
 import { CSSNode } from './css-node'
 
 /** @internal */
@@ -154,11 +154,11 @@ export class ValueParser {
 		let name_end = end - 1 // Exclude the '('
 
 		// Get function name to check for special handling
-		let func_name = this.source.substring(start, name_end).toLowerCase()
+		let func_name_substr = this.source.substring(start, name_end)
 
 		// Create URL or function node based on function name (length will be set later)
 		let node = this.arena.create_node(
-			func_name === 'url' ? URL : FUNCTION,
+			str_equals('url', func_name_substr) ? URL : FUNCTION,
 			start,
 			0, // length unknown yet
 			this.lexer.line,
@@ -171,7 +171,7 @@ export class ValueParser {
 		// Don't parse contents to preserve URLs with dots, base64, inline SVGs, etc.
 		// Users can extract the full URL from the function's text property
 		// Note: Quoted urls like url("...") or url('...') parse normally
-		if (func_name === 'url' || func_name === 'src') {
+		if (str_equals('url', func_name_substr) || str_equals('src', func_name_substr)) {
 			// Peek at the next token to see if it's a string
 			// If it's a string, parse normally. Otherwise, skip parsing children.
 			let save_pos = this.lexer.save_position()