fix(parser): fix crash when css variable property does not end with a semicolon

Fixes less#3698 less#3373

Author: b-kelly

packages/less/src/less-browser/utils.js

@@ -9,7 +9,7 @@ export function extractId(href) {
 }
 
 export function addDataAttr(options, tag) {
-	if(!tag) return; // in case of tag is null or undefined
+    if (!tag) {return;} // in case of tag is null or undefined
     for (const opt in tag.dataset) {
         if (tag.dataset.hasOwnProperty(opt)) {
             if (opt === 'env' || opt === 'dumpLineNumbers' || opt === 'rootpath' || opt === 'errorReporting') {

packages/less/src/less/parser/parser.js

@@ -1541,7 +1541,7 @@ const Parser = function Parser(context, imports, fileInfo) {
 
                         // Custom property values get permissive parsing
                         if (name[0].value && name[0].value.slice(0, 2) === '--') {
-                            value = this.permissiveValue();
+                            value = this.permissiveValue(/[;}]/);
                         }
                         // Try to store values as anonymous
                         // If we need the value later we'll re-parse it in ruleset.parseValue

packages/test-data/css/_main/permissive-parse.css

@@ -35,3 +35,12 @@ foo[attr="blah"] {
   --value: a /* { ; } */;
   --comment-within: ( /* okay?; comment; */ );
 }
+.test-no-trailing-semicolon {
+  --value: blue;
+}
+.test-no-trailing-semicolon2 {
+  --value: blue;
+}
+.test-no-trailing-semicolon3 {
+  --value: blue;
+}

packages/test-data/less/_main/permissive-parse.less

@@ -47,4 +47,9 @@
 .test-rule-comment {
   --value: a/* { ; } */;
   --comment-within: ( /* okay?; comment; */ );
-}
+}
+.test-no-trailing-semicolon {
+  --value: blue
+}
+.test-no-trailing-semicolon2 {--value: blue}
+.test-no-trailing-semicolon3 { --value: blue }