fix(parse): match color function names and keywords case-insensitively

src/hsl/parseHslLegacy.js

@@ -6,7 +6,8 @@ import { hue, per, num_per, c } from '../util/regex.js';
 	Reference: https://drafts.csswg.org/css-color/#the-hsl-notation
  */
 const hsl_old = new RegExp(
-	`^hsla?\\(\\s*${hue}${c}${per}${c}${per}\\s*(?:,\\s*${num_per}\\s*)?\\)$`
+	`^hsla?\\(\\s*${hue}${c}${per}${c}${per}\\s*(?:,\\s*${num_per}\\s*)?\\)$`,
+	'i'
 );
 
 const parseHslLegacy = color => {

src/parse.js

@@ -143,7 +143,7 @@ function identlike(chars) {
 }
 
 export function tokenize(str = '') {
-	let chars = str.trim();
+	let chars = str.trim().toLowerCase();
 	let tokens = [];
 	let ch;
 
@@ -264,10 +264,13 @@ export function parseColorSyntax(tokens) {
 	if (token.type !== Tok.Ident) {
 		return undefined;
 	}
-	const mode = colorProfiles[token.value];
-	if (!mode) {
+	// Use an own-property check so that identifiers inherited from
+	// `Object.prototype` (`constructor`, `__proto__`, …) don't resolve to
+	// truthy non-profile values and crash further down.
+	if (!Object.prototype.hasOwnProperty.call(colorProfiles, token.value)) {
 		return undefined;
 	}
+	const mode = colorProfiles[token.value];
 	const res = { mode };
 	const coords = consumeCoords(tokens, false);
 	if (!coords) {

src/rgb/parseRgbLegacy.js

@@ -5,11 +5,13 @@ import { num, per, num_per, c } from '../util/regex.js';
 	Reference: https://drafts.csswg.org/css-color/#rgb-functions
  */
 const rgb_num_old = new RegExp(
-	`^rgba?\\(\\s*${num}${c}${num}${c}${num}\\s*(?:,\\s*${num_per}\\s*)?\\)$`
+	`^rgba?\\(\\s*${num}${c}${num}${c}${num}\\s*(?:,\\s*${num_per}\\s*)?\\)$`,
+	'i'
 );
 
 const rgb_per_old = new RegExp(
-	`^rgba?\\(\\s*${per}${c}${per}${c}${per}\\s*(?:,\\s*${num_per}\\s*)?\\)$`
+	`^rgba?\\(\\s*${per}${c}${per}${c}${per}\\s*(?:,\\s*${num_per}\\s*)?\\)$`,
+	'i'
 );
 
 const parseRgbLegacy = color => {

src/rgb/parseTransparent.js

@@ -1,5 +1,5 @@
 const parseTransparent = c =>
-	c === 'transparent'
+	c?.toLowerCase() === 'transparent'
 		? { mode: 'rgb', r: 0, g: 0, b: 0, alpha: 0 }
 		: undefined;
 

src/util/hue.js

@@ -1,5 +1,5 @@
 const hueToDeg = (val, unit) => {
-	switch (unit) {
+	switch (unit?.toLowerCase()) {
 		case 'deg':
 			return +val;
 		case 'rad':

test/parse.test.js

@@ -1,6 +1,6 @@
 import test from 'node:test';
 import assert from 'node:assert';
-import { parse } from '../src/index.js';
+import { parse, parseTransparent } from '../src/index.js';
 
 test('named colors', t => {
 	assert.deepEqual(
@@ -408,3 +408,97 @@ test('undefined', t => {
 test('Issue #204', t => {
 	assert.equal(parse('oklch(70% 0..1 156)'), undefined);
 });
+
+test('case-insensitive function names and keywords', t => {
+	// Function names are ASCII case-insensitive in CSS.
+	assert.deepEqual(parse('RGB(255 0 0)'), parse('rgb(255 0 0)'), 'RGB()');
+	assert.deepEqual(
+		parse('RGBA(255, 0, 0, 0.5)'),
+		parse('rgba(255, 0, 0, 0.5)'),
+		'RGBA() legacy'
+	);
+	assert.deepEqual(
+		parse('HSL(120 50% 50%)'),
+		parse('hsl(120 50% 50%)'),
+		'HSL()'
+	);
+	assert.deepEqual(
+		parse('HSLA(120, 50%, 50%, 0.5)'),
+		parse('hsla(120, 50%, 50%, 0.5)'),
+		'HSLA() legacy'
+	);
+	assert.deepEqual(parse('HWB(120 0% 0%)'), parse('hwb(120 0% 0%)'), 'HWB()');
+	assert.deepEqual(parse('LAB(50 0 0)'), parse('lab(50 0 0)'), 'LAB()');
+	assert.deepEqual(parse('LCH(50 40 30)'), parse('lch(50 40 30)'), 'LCH()');
+	assert.deepEqual(
+		parse('OkLCH(0.5 0.1 30)'),
+		parse('oklch(0.5 0.1 30)'),
+		'OkLCH() (mixed case)'
+	);
+
+	// Color-space identifiers inside color() are case-insensitive too.
+	assert.deepEqual(
+		parse('COLOR(DISPLAY-P3 1 0 0)'),
+		parse('color(display-p3 1 0 0)'),
+		'color() with uppercase profile'
+	);
+
+	// Hue angle units are case-insensitive, in both modern and legacy syntax.
+	assert.deepEqual(
+		parse('hsl(120DEG 50% 50%)'),
+		parse('hsl(120deg 50% 50%)'),
+		'uppercase hue unit (modern)'
+	);
+	assert.deepEqual(
+		parse('hsl(0.5TURN, 50%, 50%)'),
+		parse('hsl(0.5turn, 50%, 50%)'),
+		'uppercase hue unit (legacy)'
+	);
+
+	// The `transparent` keyword is case-insensitive.
+	assert.deepEqual(
+		parse('TRANSPARENT'),
+		{ mode: 'rgb', r: 0, g: 0, b: 0, alpha: 0 },
+		'TRANSPARENT'
+	);
+});
+
+test('color() with a non-profile identifier returns undefined', t => {
+	// Identifiers inherited from Object.prototype must not resolve to a
+	// truthy value in the color-space lookup (and must not throw).
+	assert.equal(parse('color(__proto__ 1 0 0)'), undefined, '__proto__');
+	assert.equal(parse('color(constructor 1 0 0)'), undefined, 'constructor');
+	assert.equal(parse('color(CONSTRUCTOR 1 0 0)'), undefined, 'CONSTRUCTOR');
+	assert.equal(parse('color(toString 1 0 0)'), undefined, 'toString');
+});
+
+test('parseTransparent accepts absent colors', t => {
+	assert.equal(parseTransparent(), undefined);
+	assert.equal(parseTransparent(null), undefined);
+	assert.equal(parseTransparent(''), undefined);
+	assert.equal(parseTransparent('red'), undefined);
+	assert.deepEqual(parseTransparent('TrAnSpArEnT'), {
+		mode: 'rgb',
+		r: 0,
+		g: 0,
+		b: 0,
+		alpha: 0
+	});
+});
+
+test('case-insensitive keywords and exponential notation', t => {
+	assert.deepEqual(parse('  RGB(1E2 NoNe 0 / NoNe)  '), {
+		mode: 'rgb',
+		r: 100 / 255,
+		b: 0
+	});
+});
+
+test('case-insensitive hue units in modern and legacy syntax', t => {
+	for (const unit of ['DEG', 'RAD', 'GRAD', 'TURN']) {
+		for (const separator of [' ', ', ']) {
+			const color = `HSL(0.5${unit}${separator}50%${separator}50%)`;
+			assert.deepEqual(parse(color), parse(color.toLowerCase()), color);
+		}
+	}
+});