Assign supplementary private-use planes before Unicode 3.0.1

UnicodeData from Unicode 2.0 through 3.0.0 lists the Private Use High
Surrogates but not the planes 15 and 16 private-use characters their
surrogate pairs encode, so those planes were reported as unassigned.
Unicode 3.0.1 added the ranges to the file, and its documentation
describes them as the characters those surrogate pairs represent.

Assisted-By: Claude Opus 5.5

Author: JLHwung

scripts/parse-blocks-scripts-properties.mjs

@@ -195,6 +195,7 @@ const parseDerivedGeneralCategory = async (version) => {
 		let flag = false;
 		let first = 0;
 		let lastCodePoint = -1;
+		let hasPrivateUseHighSurrogates = false;
 		// Unicode 1.1.5 lists only U+4E00 as a representative of the Unified
 		// Han ideographs. The Unicode 1.1 Han cross-reference table assigns the
 		// whole 4E00..9FA5 range:
@@ -241,6 +242,8 @@ const parseDerivedGeneralCategory = async (version) => {
 				if (/<.+, First>/.test(name)) {
 					flag = true;
 					first = codePoint;
+					hasPrivateUseHighSurrogates ||=
+						name === '<Private Use High Surrogate, First>';
 				} else {
 					for (const category of categories) {
 						categoryMap[category].addRange(codePoint, recordEnd);
@@ -266,6 +269,13 @@ const parseDerivedGeneralCategory = async (version) => {
 			// Unicode 1.1 Han cross-reference table lists as F900..FA2D.
 			unlistedRanges.push([0xf900, 0xfa2d, 'Lo']);
 		}
+		if (hasPrivateUseHighSurrogates && lastCodePoint < 0x10000) {
+			// Before Unicode 3.0.1, UnicodeData lists the Private Use High
+			// Surrogates but not the planes 15 and 16 private-use characters
+			// their surrogate pairs encode. Unicode 3.0.1 added those ranges:
+			// https://www.unicode.org/Public/3.0-Update1/UnicodeData-3.0.1.html
+			unlistedRanges.push([0xf0000, 0xffffd, 'Co'], [0x100000, 0x10fffd, 'Co']);
+		}
 		for (const [start, end, generalCategory] of unlistedRanges) {
 			// Undo the gap handling, which recorded the range as unassigned.
 			for (const category of [

tests/parsers.mjs

@@ -186,6 +186,24 @@ test('Unicode 1.1.5 assigns the unlisted CJK compatibility ideographs', async (t
 	}
 });
 
+test('Supplementary private-use planes are assigned from Unicode 2.0', async (t) => {
+	for (const version of ['2.0.14', '2.1.9', '3.0.0', '3.0.1', '3.1.0']) {
+		const categories = await parseDerivedGeneralCategory(version);
+		for (const cp of [0xf0000, 0xffffd, 0x100000, 0x10fffd]) {
+			const message = `${version}: ${cp.toString(16)}`;
+			t.assert.ok(categories.Private_Use.contains(cp), message);
+			t.assert.ok(categories.Assigned.contains(cp), message);
+			t.assert.ok(!categories.Unassigned.contains(cp), message);
+		}
+		for (const cp of [0xeffff, 0xffffe, 0xfffff, 0x10ffff]) {
+			const message = `${version}: ${cp.toString(16)}`;
+			t.assert.ok(categories.Unassigned.contains(cp), message);
+		}
+	}
+	const categories = await parseDerivedGeneralCategory('1.1.5');
+	t.assert.ok(categories.Unassigned.contains(0xf0000));
+});
+
 test('Bidi class applies historical and current unassigned defaults', async (t) => {
 	for (const version of [
 		'3.0.0',