fix(color-contrast): allow disabled label children

Closes #596

Author: Marcy Sutton

lib/rules/color-contrast-matches.js

@@ -35,8 +35,12 @@ if (nodeName === 'FIELDSET' && node.disabled || axe.commons.dom.findUp(node, 'fi
 var nodeParentLabel = axe.commons.dom.findUp(node, 'label');
 if (nodeName === 'LABEL' || nodeParentLabel) {
 	var relevantNode = node;
+	var relevantVirtualNode = virtualNode;
+
 	if (nodeParentLabel) {
 		relevantNode = nodeParentLabel;
+		// we need an input candidate from a parent to account for label children
+		relevantVirtualNode = axe.utils.getNodeFromTree(axe._tree[0], nodeParentLabel);
 	}
 	// explicit label of disabled input
 	let doc = axe.commons.dom.getRootNode(relevantNode);
@@ -45,7 +49,7 @@ if (nodeName === 'LABEL' || nodeParentLabel) {
 		return false;
 	}
 
-	var candidate = axe.utils.querySelectorAll(virtualNode, 'input:not([type="hidden"]):not([type="image"])' +
+	var candidate = axe.utils.querySelectorAll(relevantVirtualNode, 'input:not([type="hidden"]):not([type="image"])' +
 		':not([type="button"]):not([type="submit"]):not([type="reset"]), select, textarea');
 	if (candidate.length && candidate[0].actualNode.disabled) {
 		return false;

test/rule-matches/color-contrast-matches.js

@@ -149,7 +149,18 @@ describe('color-contrast-matches', function () {
 		var target = fixture.querySelector('input');
 		var tree = axe._tree = axe.utils.getFlattenedTree(fixture);
 		assert.isFalse(rule.matches(target, axe.utils.getNodeFromTree(tree[0], target)));
+	});
 
+	it('should not match a disabled implicit label child', function () {
+		fixture.innerHTML = '<label>' +
+			'<input type="checkbox" style="position: absolute;display: inline-block;width: 1.5rem;height: 1.5rem;opacity: 0;" disabled checked>' +
+			'<span style="background-color:rgba(0, 0, 0, 0.26);display:inline-block;width: 1.5rem;height: 1.5rem;" aria-hidden="true"></span>' +
+			'<span style="color:rgba(0, 0, 0, 0.38);" id="target">Baseball</span>' +
+			'</label>';
+		var target = fixture.querySelector('#target');
+		var tree = axe._tree = axe.utils.getFlattenedTree(fixture);
+		var result = rule.matches(target, axe.utils.getNodeFromTree(tree[0], target));
+		assert.isFalse(result);
 	});
 
 	it('should not match <textarea disabled>', function () {