Make longer and undefined/same hues have parity with CSS spec (#474)

* Make longer and undefined have parity with CSS spec

* Don't correct hues until after raw angles are returned

* Doesn't just apply to undefined

src/angles.js

@@ -1,13 +1,31 @@
+import * as util from "./util.js";
+
 export function constrain (angle) {
 	return ((angle % 360) + 360) % 360;
 }
 
 export function adjust (arc, angles) {
+	let [a1, a2] = angles;
+
+	let none1 = util.isNone(a1);
+	let none2 = util.isNone(a2);
+
+	if (none1 && none2) {
+		return [a1, a2];
+	}
+	else if (none1) {
+		a1 = a2;
+	}
+	else if (none2) {
+		a2 = a1;
+	}
+
 	if (arc === "raw") {
 		return angles;
 	}
 
-	let [a1, a2] = angles.map(constrain);
+	a1 = constrain(a1);
+	a2 = constrain(a2);
 
 	let angleDiff = a2 - a1;
 

test/angles.js

@@ -31,5 +31,15 @@ export default {
 			args: ["raw", [-20, 380]],
 			expect: [-20, 380],
 		},
+		{
+			name: "Longer and Undefined",
+			args: ["longer", [90, NaN]],
+			expect: [90, 450],
+		},
+		{
+			name: "Longer and Same Hues",
+			args: ["longer", [90, 90]],
+			expect: [90, 450],
+		},
 	],
 };