Add more tests and simplify implementation

Fixes #66

Author: sindresorhus

index.js

@@ -6,7 +6,7 @@ Logic:
 - Segment graphemes to match how terminals render clusters.
 - Width rules:
 	1. Skip non-printing clusters (Default_Ignorable, Control, pure Mark, lone Surrogates). Tabs are ignored by design.
-	2. Emoji clusters are double-width only when VS16 is present, the base has Emoji_Presentation (and not VS15), or the cluster has multiple scalars (flags, ZWJ, keycaps, tags, etc.).
+	2. RGI emoji clusters (\p{RGI_Emoji}) are double-width.
 	3. Otherwise use East Asian Width of the cluster’s first visible code point, and add widths for trailing Halfwidth/Fullwidth Forms within the same cluster (e.g., dakuten/handakuten/prolonged sound mark).
 */
 
@@ -20,8 +20,6 @@ const leadingNonPrintingRegex = /^[\p{Default_Ignorable_Code_Point}\p{Control}\p
 
 // RGI emoji sequences
 const rgiEmojiRegex = /^\p{RGI_Emoji}$/v;
-// Default emoji presentation (single-scalar emoji without VS16)
-const emojiPresentationRegex = /^\p{Emoji_Presentation}$/v;
 
 function baseVisible(segment) {
 	return segment.replace(leadingNonPrintingRegex, '');
@@ -31,29 +29,6 @@ function isZeroWidthCluster(segment) {
 	return zeroWidthClusterRegex.test(segment);
 }
 
-function isDoubleWidthEmojiCluster(segment) {
-	const hasVs16 = segment.includes('\uFE0F');
-
-	if (hasVs16) {
-		return true;
-	}
-
-	const visible = baseVisible(segment);
-	const baseScalar = visible.codePointAt(0);
-	const baseChar = String.fromCodePoint(baseScalar);
-	const baseIsEmojiPresentation = emojiPresentationRegex.test(baseChar);
-	const hasVs15 = segment.includes('\uFE0E');
-
-	if (baseIsEmojiPresentation && !hasVs15) {
-		return true;
-	}
-
-	const codePointCount = [...segment].length;
-	const multiScalarMeaningful = codePointCount > 1 && !(codePointCount === 2 && hasVs15 && !hasVs16);
-
-	return multiScalarMeaningful;
-}
-
 function trailingHalfwidthWidth(segment, eastAsianWidthOptions) {
 	let extra = 0;
 	if (segment.length > 1) {
@@ -97,7 +72,7 @@ export default function stringWidth(input, options = {}) {
 		}
 
 		// Emoji width logic
-		if (rgiEmojiRegex.test(segment) && isDoubleWidthEmojiCluster(segment)) {
+		if (rgiEmojiRegex.test(segment)) {
 			width += 2;
 			continue;
 		}

test.js

@@ -158,3 +158,94 @@ test('prepend + emoji', macro, '\u0600😀', 2);
 
 // Sequence consisting only of default ignorables should be zero
 test('only default ignorables (tags)', macro, '\u{E0020}\u{E007F}', 0);
+
+// Emoji coverage for RGI and related cases
+// Case 1: Emoji with VS16 (should be double-width)
+test('digit with VS16 (keycap base)', macro, '0\uFE0F', 1); // Digits/asterisk/pound are not RGI emoji
+test('asterisk with VS16', macro, '*\uFE0F', 1);
+test('pound with VS16', macro, '#\uFE0F', 1);
+test('trademark with VS16', macro, '™\uFE0F', 2);
+test('watch with VS16', macro, '⌚\uFE0F', 2);
+test('phone with VS16', macro, '☎\uFE0F', 2);
+test('keyboard with VS16', macro, '⌨\uFE0F', 2);
+test('envelope with VS16', macro, '✉\uFE0F', 2);
+
+// Case 2: Emoji_Presentation characters without VS15 (should be double-width)
+test('face emoji (has Emoji_Presentation)', macro, '😀', 2);
+test('heart emoji (has Emoji_Presentation)', macro, '❤️', 2);
+test('fire emoji (has Emoji_Presentation)', macro, '🔥', 2);
+test('rocket emoji (has Emoji_Presentation)', macro, '🚀', 2);
+test('star emoji (has Emoji_Presentation)', macro, '⭐', 2);
+
+// Case 3: Emoji_Presentation with VS15 (should be single-width)
+test('heart with VS15 (text style)', macro, '❤\uFE0E', 1);
+test('star with VS15 (text style)', macro, '⭐\uFE0E', 2); // Star with VS15 still renders as 2 in terminals
+
+// Case 4: Multi-scalar meaningful sequences (should be double-width)
+test('keycap sequence 0️⃣', macro, '0️⃣', 2);
+test('keycap sequence 1️⃣', macro, '1️⃣', 2);
+test('keycap sequence 9️⃣', macro, '9️⃣', 2);
+test('keycap sequence *️⃣', macro, '*️⃣', 2);
+test('keycap sequence #️⃣', macro, '#️⃣', 2);
+test('flag emoji GB', macro, '🇬🇧', 2);
+test('flag emoji JP', macro, '🇯🇵', 2);
+test('skin tone modifier', macro, '👋🏻', 2);
+test('skin tone modifier dark', macro, '👋🏿', 2);
+test('couple with heart', macro, '👨‍❤️‍👨', 2);
+test('woman technologist', macro, '👩‍💻', 2);
+test('man health worker', macro, '👨‍⚕️', 2);
+
+// Case 5: Non-emoji presentation without VS16 (should be single-width via EAW)
+test('watch without VS', macro, '⌚', 2); // Watch is actually RGI emoji with Emoji_Presentation
+test('phone without VS (not Emoji_Presentation)', macro, '☎', 1);
+test('keyboard without VS (not Emoji_Presentation)', macro, '⌨', 1);
+test('envelope without VS (not Emoji_Presentation)', macro, '✉', 1);
+
+// Case 6: Edge cases for multi-scalar logic
+test('single code point with VS15 (2 scalars but not meaningful)', macro, 'A\uFE0E', 1);
+test('emoji with VS15 only (2 scalars, VS15 present)', macro, '⌚\uFE0E', 2); // Watch with VS15 still renders as 2
+test('three code points with VS15 at end', macro, 'A👋\uFE0E', 3);
+
+// Case 7: RGI emoji coverage
+test('RGI emoji face', macro, '😊', 2);
+test('RGI emoji hand', macro, '✋', 2);
+test('RGI emoji animal', macro, '🐶', 2);
+test('RGI emoji food', macro, '🍕', 2);
+test('RGI emoji flag', macro, '🏁', 2);
+
+// Case 8: Complex emoji sequences that test all branches
+test('emoji with combining mark', macro, '😀\u0301', 2);
+test('emoji with ZWJ and another emoji', macro, '😀\u200D😀', 2);
+test('text character made emoji with VS16', macro, '↔\uFE0F', 2);
+test('text character kept text with VS15', macro, '↔\uFE0E', 1);
+
+// Case 9: Non-RGI sequences
+test('non-RGI with VS16', macro, '〰\uFE0F', 2);
+test('non-RGI multi-scalar', macro, '☎\uFE0F\u20E3', 1); // Not RGI emoji, counts as 1
+
+// Case 10: VS15 on Emoji_Presentation remain width 2 in most terminals via EAW
+test('hourglass with VS15', macro, '⌛\uFE0E', 2);
+test('fast-forward with VS15', macro, '⏩\uFE0E', 2);
+test('rewind with VS15', macro, '⏪\uFE0E', 2);
+test('arrow double up with VS15', macro, '⏫\uFE0E', 2);
+test('arrow double down with VS15', macro, '⏬\uFE0E', 2);
+test('alarm clock with VS15', macro, '⏰\uFE0E', 2);
+test('hourglass flowing sand with VS15', macro, '⏳\uFE0E', 2);
+test('umbrella with rain with VS15', macro, '☔\uFE0E', 2);
+test('hot beverage with VS15', macro, '☕\uFE0E', 2);
+// Removed redundant duplicate of '⭐\uFE0E' test
+
+// Other emoji that may not have Emoji_Presentation but are affected
+test('sun with VS15', macro, '☀\uFE0E', 1);
+test('cloud with VS15', macro, '☁\uFE0E', 1);
+test('umbrella with VS15', macro, '☂\uFE0E', 1);
+test('snowman with VS15', macro, '☃\uFE0E', 1);
+test('comet with VS15', macro, '☄\uFE0E', 1);
+test('black nib with VS15', macro, '✒\uFE0E', 1);
+test('heavy check mark with VS15', macro, '✔\uFE0E', 1);
+
+// More edge cases for single-scalar text characters (not emoji)
+test('digit zero as plain text (not emoji)', macro, '0', 1);
+test('digit one as plain text', macro, '1', 1);
+test('asterisk as plain text', macro, '*', 1);
+test('hash as plain text', macro, '#', 1);