Fix: Sparse arrays in rules with spacing and commas

For `disallowCommaBeforeLineBreak` and `requireCommaBeforeLineBreak`

Fixes #1909
Closes gh-1969

Author: bjdixon

lib/rules/disallow-comma-before-line-break.js

@@ -104,13 +104,15 @@ module.exports.prototype = {
         }
 
         file.iterateTokensByTypeAndValue('Punctuator', ',', function(token) {
-            if (canSkip(token)) {
+            var nextToken = file.getNextToken(token);
+
+            if (canSkip(token) || nextToken.value === ',') {
                 return;
             }
 
             errors.assert.sameLine({
                 token: token,
-                nextToken: file.getNextToken(token),
+                nextToken: nextToken,
                 message: 'Commas should be placed on the same line as value'
             });
 

lib/rules/require-comma-before-line-break.js

@@ -52,8 +52,13 @@ module.exports.prototype = {
 
     check: function(file, errors) {
         file.iterateTokensByTypeAndValue('Punctuator', ',', function(token) {
+            var prevToken = file.getPrevToken(token);
+
+            if (prevToken.value === ',') {
+                return;
+            }
             errors.assert.sameLine({
-                token: file.getPrevToken(token),
+                token: prevToken,
                 nextToken: token,
                 message: 'Commas should not be placed on new line'
             });

test/specs/rules/disallow-comma-before-line-break.js

@@ -44,6 +44,10 @@ describe('rules/disallow-comma-before-line-break', function() {
         expect(checker.checkString('var a = [1\n,2];')).to.have.no.errors();
     });
 
+    it('should not report legal comma placement in multiline sparse array declaration', function() {
+        expect(checker.checkString('var a = [1\n,\n,\n,2];')).to.have.no.errors();
+    });
+
     it('should not report legal comma placement in multiline object declaration', function() {
         expect(checker.checkString('var a = {a:1\n,c:3};')).to.have.no.errors();
     });

test/specs/rules/require-comma-before-line-break.js

@@ -32,6 +32,10 @@ describe('rules/require-comma-before-line-break', function() {
         expect(checker.checkString('var a = [1,\n2];')).to.have.no.errors();
     });
 
+    it('should not report legal comma placement in multiline sparse array declaration', function() {
+        expect(checker.checkString('var a = [1,\n,\n,\n2];')).to.have.no.errors();
+    });
+
     it('should not report legal comma placement in multiline object declaration', function() {
         expect(checker.checkString('var a = {a:1,\nc:3};')).to.have.no.errors();
     });