Add support for dynamic import operator to JavaScript mode (#5259)

Author: tmcw

mode/javascript/javascript.js

@@ -400,6 +400,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     if (type == "{") return contCommasep(objprop, "}", null, maybeop);
     if (type == "quasi") return pass(quasi, maybeop);
     if (type == "new") return cont(maybeTarget(noComma));
+    if (type == "import") return cont(expression);
     return cont();
   }
   function maybeexpression(type) {
@@ -726,6 +727,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
   }
   function afterImport(type) {
     if (type == "string") return cont();
+    if (type == "(") return pass(expression);
     return pass(importSpec, maybeMoreImports, maybeFrom);
   }
   function importSpec(type, value) {

mode/javascript/test.js

@@ -63,6 +63,12 @@
   MT("import_trailing_comma",
      "[keyword import] {[def foo], [def bar],} [keyword from] [string 'baz']")
 
+  MT("import_dynamic",
+     "[keyword import]([string 'baz']).[property then]")
+
+  MT("import_dynamic",
+     "[keyword const] [def t] [operator =] [keyword import]([string 'baz']).[property then]")
+
   MT("const",
      "[keyword function] [def f]() {",
      "  [keyword const] [[ [def a], [def b] ]] [operator =] [[ [number 1], [number 2] ]];",