Allow sourceType: module even with ecmaVersion < 6

acorn-loose/src/statement.js

@@ -10,9 +10,7 @@ lp.parseTopLevel = function() {
  while (this.tok.type !== tt.eof) node.body.push(this.parseStatement())
  this.toks.adaptDirectivePrologue(node.body)
  this.last = this.tok
- if (this.options.ecmaVersion >= 6) {
- node.sourceType = this.options.sourceType
- }
+ node.sourceType = this.options.sourceType
  return this.finishNode(node, "Program")
 }
 

acorn/README.md

@@ -64,6 +64,9 @@ an object containing any of these fields:
  either `"script"` or `"module"`. This influences global strict mode
  and parsing of `import` and `export` declarations.
 
+ **NOTE**: If set to `"module"`, then static `import` / `export` syntax
+ will be valid, even if `ecmaVersion` is less than 6.
+
 - **onInsertedSemicolon**: If given a callback, that callback will be
  called whenever a missing semicolon is inserted by the parser. The
  callback will be given the character offset of the point where the

acorn/src/state.js

@@ -9,7 +9,7 @@ export class Parser {
  constructor(options, input, startPos) {
  this.options = options = getOptions(options)
  this.sourceFile = options.sourceFile
- this.keywords = wordsRegexp(keywords[options.ecmaVersion >= 6 ? 6 : 5])
+ this.keywords = wordsRegexp(keywords[options.ecmaVersion >= 6 ? 6 : options.sourceType === "module" ? "5module" : 5])
  let reserved = ""
  if (options.allowReserved !== true) {
  for (let v = options.ecmaVersion;; v--)

acorn/src/statement.js

@@ -27,9 +27,7 @@ pp.parseTopLevel = function(node) {
  this.raiseRecoverable(this.undefinedExports[name].start, `Export '${name}' is not defined`)
  this.adaptDirectivePrologue(node.body)
  this.next()
- if (this.options.ecmaVersion >= 6) {
- node.sourceType = this.options.sourceType
- }
+ node.sourceType = this.options.sourceType
  return this.finishNode(node, "Program")
 }
 

test/tests.js

@@ -7,6 +7,35 @@ if (typeof exports != "undefined") {
  var acorn = require("../acorn");
 }
 
+test("import ''", {
+ type: "Program",
+ start: 0,
+ end: 9,
+ body: [
+ {
+ type: "ImportDeclaration",
+ start: 0,
+ end: 9,
+ specifiers: [],
+ source: {
+ type: "Literal",
+ start: 7,
+ end: 9,
+ value: "",
+ raw: "''"
+ }
+ }
+ ]
+}, {
+ ecmaVersion: 5,
+ sourceType: "module"
+});
+
+testFail("import('')", "Unexpected token (1:6)", {
+ ecmaVersion: 5,
+ sourceType: "module"
+});
+
 test("new Object", {
  type: "Program",
  start: 0,