"selector-newline": look for newline characters in selectors

Usually it's a forgotten comma, not a descendant combinator.
Closes gh-282

Author: mahonnaise

src/rules/selector-newline.js

@@ -0,0 +1,34 @@
+/*
+ * Rule: Avoid new-line characters in selectors.
+ */
+
+CSSLint.addRule({
+
+    //rule information
+    id: "selector-newline",
+    name: "Disallow new-line characters in selectors",
+    desc: "New-line characters in selectors are usually a forgotten comma and not a descendant combinator.",
+    browsers: "All",
+
+    //initialization
+    init: function(parser, reporter) {
+        var rule = this;
+
+        parser.addListener("startrule", function(event) {
+            var i, len, selector, p, pLen, part, previousLine, currentLine,
+                selectors = event.selectors;
+
+            for (i = 0, len = selectors.length; i < len; i++) {
+                selector = selectors[i];
+                for (p = 0, pLen = selector.parts.length; p < pLen; p++) {
+                    part = selector.parts[p];
+                    currentLine = part.line;
+                    if (currentLine === previousLine) {
+                        reporter.report("newline character found in selector (forgot a comma?)", currentLine, selectors[i].parts[0].col, rule);
+                    }
+                    previousLine = currentLine;
+                }
+            }
+        });
+    }
+});

tests/rules/selector-newline.js

@@ -0,0 +1,34 @@
+/*global YUITest, CSSLint*/
+(function () {
+
+    var ruleId = "selector-newline", expectWarning, expectPass;
+
+    expectWarning = function (ruleset, expectedMessage) {
+        var result, enabledRules = {};
+        enabledRules[ruleId] = 1;
+        result = CSSLint.verify(ruleset, enabledRules);
+        YUITest.Assert.areEqual(1, result.messages.length);
+        YUITest.Assert.areEqual("warning", result.messages[0].type);
+        YUITest.Assert.areEqual(expectedMessage, result.messages[0].message);
+    };
+
+    expectPass = function (ruleset) {
+        var result, enabledRules = {};
+        enabledRules[ruleId] = 1;
+        result = CSSLint.verify(ruleset, enabledRules);
+        YUITest.Assert.areEqual(0, result.messages.length);
+    };
+
+    YUITest.TestRunner.add(new YUITest.TestCase({
+
+        name: ruleId + " Rule Errors",
+
+        "a newline in a selector should result in a warning": function () {
+            expectWarning(".foo\n.bar{}", "newline character found in selector (forgot a comma?)");
+        },
+        "a newline between selectors should not result in a warning": function () {
+            expectPass(".foo,\n.bar{}");
+        }
+    }));
+
+}());