optimise for ternary expressions when excluding unused css (#696)

src/css/Selector.ts

@@ -1,4 +1,5 @@
 import MagicString from 'magic-string';
+import { gatherPossibleValues, UNKNOWN } from './gatherPossibleValues';
 import { Validator } from '../validate/index';
 import { Node } from '../interfaces';
 
@@ -192,12 +193,22 @@ function attributeMatches(node: Node, name: string, expectedValue: string, opera
 	const attr = node.attributes.find((attr: Node) => attr.name === name);
 	if (!attr) return false;
 	if (attr.value === true) return operator === null;
-	if (isDynamic(attr.value)) return true;
+	if (attr.value.length > 1) return true;
-
-	const actualValue = attr.value[0].data;
 
 	const pattern = operators[operator](expectedValue, caseInsensitive ? 'i' : '');
-	return pattern.test(actualValue);
+	const value = attr.value[0];
+
+	if (value.type === 'Text') return pattern.test(value.data);
+
+	const possibleValues = new Set();
+	gatherPossibleValues(value.expression, possibleValues);
+	if (possibleValues.has(UNKNOWN)) return true;
+
+	for (const x of Array.from(possibleValues)) { // TypeScript for-of is slightly unlike JS
+		if (pattern.test(x)) return true;
+	}
+
+	return false;
 }
 
 function isDynamic(value: Node) {

src/css/gatherPossibleValues.ts

@@ -0,0 +1,18 @@
+import { Node } from '../interfaces';
+
+export const UNKNOWN = {};
+
+export function gatherPossibleValues(node: Node, set: Set<string|{}>) {
+	if (node.type === 'Literal') {
+		set.add(node.value);
+	}
+
+	else if (node.type === 'ConditionalExpression') {
+		gatherPossibleValues(node.consequent, set);
+		gatherPossibleValues(node.alternate, set);
+	}
+
+	else {
+		set.add(UNKNOWN);
+	}
+}

test/css/index.js

@@ -13,7 +13,7 @@ function tryRequire(file) {
 }
 
 function normalizeWarning(warning) {
-	warning.frame = warning.frame.replace(/^\n/, '').replace(/^\t+/gm, '');
+	warning.frame = warning.frame.replace(/^\n/, '').replace(/^\t+/gm, '').replace(/\s+$/gm, '');
 	delete warning.filename;
 	delete warning.toString;
 	return warning;

test/css/samples/unused-selector-ternary/_config.js

@@ -0,0 +1,24 @@
+export default {
+	cascade: false,
+
+	data: {
+		active: true
+	},
+
+	warnings: [{
+		filename: "SvelteComponent.html",
+		message: "Unused CSS selector",
+		loc: {
+			line: 12,
+			column: 1
+		},
+		pos: 125,
+		frame: `
+			10:   }
+			11:
+			12:   .maybeactive {
+			      ^
+			13:     color: green;
+			14:   }`
+	}]
+};

test/css/samples/unused-selector-ternary/expected.css

@@ -0,0 +1 @@
+.active[svelte-xyz]{color:red}.inactive[svelte-xyz]{color:blue}

test/css/samples/unused-selector-ternary/expected.html

@@ -0,0 +1 @@
+<div svelte-xyz="" class="active"></div>

test/css/samples/unused-selector-ternary/input.html

@@ -0,0 +1,15 @@
+<div class='{{active ? "active": "inactive"}}'></div>
+
+<style>
+	.active {
+		color: red;
+	}
+
+	.inactive {
+		color: blue;
+	}
+
+	.maybeactive {
+		color: green;
+	}
+</style>

test/css/samples/unused-selector/warnings.json

@@ -1,10 +0,0 @@
-[{
-	"filename": "SvelteComponent.html",
-	"message": "Unused CSS selector",
-	"loc": {
-		"line": 8,
-		"column": 1
-	},
-	"pos": 61,
-	"frame": " 6:   }\n 7: \n 8:   .bar {\n      ^\n 9:     color: blue;\n10:   }"
-}]