fix: change keyword plugin and import regexp (#3668)

* fix: change the  and  regexp match

* feat: change unit test

* chore: change desc

Author: iChenLei

.gitignore

@@ -6,6 +6,7 @@
 .idea
 *.iml
 *.sublime-*
+.DS_Store
 
 # npm
 node_modules

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

@@ -1684,7 +1684,7 @@ const Parser = function Parser(context, imports, fileInfo) {
                 let features;
                 const index = parserInput.i;
 
-                const dir = parserInput.$re(/^@import?\s+/);
+                const dir = parserInput.$re(/^@import\s+/);
 
                 if (dir) {
                     const options = (dir ? this.importOptions() : null) || {};
@@ -1844,7 +1844,7 @@ const Parser = function Parser(context, imports, fileInfo) {
                 let args;
                 let options;
                 const index = parserInput.i;
-                const dir   = parserInput.$re(/^@plugin?\s+/);
+                const dir   = parserInput.$re(/^@plugin\s+/);
 
                 if (dir) {
                     args = this.pluginArgs();

packages/test-data/css/_main/impor.css

@@ -0,0 +1 @@
+@impor "impor-typo-dont-parse-as-@import.less";

packages/test-data/css/_main/plugi.css

@@ -0,0 +1 @@
+@plugi "plugi-typo-dont-parse-as-@plugin";

packages/test-data/less/_main/impor.less

@@ -0,0 +1,5 @@
+// https://github.com/less/less.js/issues/3660
+// const dir = parserInput.$re(/^@import?\s+/);
+// correct regexp is /^@import\s+/
+// so follow code will change nothing, parse result is same with raw less code
+@impor "impor-typo-dont-parse-as-@import.less";

packages/test-data/less/_main/plugi.less

@@ -0,0 +1,5 @@
+// https://github.com/less/less.js/issues/3660
+// const dir = parserInput.$re(/^@plugin?\s+/);
+// correct regexp is /^@plugin\s+/
+// so follow code will change nothing, parse result is same with raw less code
+@plugi "plugi-typo-dont-parse-as-@plugin";